JPS63183434A - Method for determining image processing condition - Google Patents

Abstract

PURPOSE:To remove the influence of noise by differentiating image data in each position, detecting a radiation field from the differential value and determining an image processing condition based on an image signal in the radiation field in case of determining the condition from a recording medium for radiation image information recorded through a radiation field stop. CONSTITUTION:When an image photographed on an accumulative phosphor sheet 1 to be a recording medium through a rectangular radiation field stop shown by an alternate long and short dash line, a digital signal f(x,y) in each picture element is found out to obtain Fig.(a) at first, and then a means value F(x,y) for every three picture elements in the (y) axis direction to obtain Fig.(b). These values are differentiated along the (x) axis and a difference F(1,2)-F(2,2)=DELTA(1,2) or the like is found out to obtain Fig.(c). Similar processing is executed also in the (x) axis direction and the outlines 2a, 2b of the radiation field stop can be determined by tracing the larger part of the difference. Consequently, noise due to dispersion on the outside of the contour of the radiation field stop can be removed and an optimum image processing condition for reproducing a visual image can be obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is for reproducing visible images read from a recording medium such as a stimulable phosphor sheet on which radiation image information is recorded by applying irradiation field aperture. The present invention relates to a method for determining image processing conditions used when processing an image signal.

(Prior art) When a certain type of phosphor is irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.), a part of this radiation energy is accumulated in the phosphor, and this It is known that when a phosphor is irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence depending on the accumulated energy, and phosphors that exhibit this property are called stimulable phosphors. .

This stimulable phosphor is used to record radiographic image information of subjects such as the human body on a sheet-shaped stimulable phosphor)
Then, the stimulable phosphor sheet is scanned with excitation light such as a laser beam to generate stimulated luminescence light, and this stimulated luminescence light is read in a charged manner to reproduce a visible image. A book reading image signal is obtained, this book reading image signal is subjected to image processing, and a radiation image of the subject is made visible on a recording material such as a photosensitive material or a display device such as a CRT based on the book reading image signal that has been subjected to image processing. The applicant has already proposed a radiation image information recording and reproducing system that outputs the information as an image. (Unexamined Japanese Patent Publication No. 55-1242
No. 9, No. 56-11395, etc. Note that in this specification, the reading of the image signal for the above-mentioned visible image reproduction is referred to as main reading, and the image signal obtained by this main reading is referred to as the main reading image signal.

Furthermore, the terms "real reading" and "real reading image signal" are used with the same meanings even when the recording medium is other than a stimulable phosphor sheet.

Image processing in the above system is generally performed based on image processing conditions determined based on the area to be imaged and the imaging method to obtain a visible image suitable for diagnostic purposes for each individual image. However, for example, it is based on the actual reading image signal, for example, the histogram (histogram of the image signal level) of the actual reading image signal, or based on the actual reading image signal and the above imaging site/imaging method, rather than the above-mentioned imaging site or imaging method.
It is also conceivable to decide based on both the photographing method and the photographing method.

In this way, it is determined based on the histogram of the main reading image signal that directly carries the characteristics of each image, and 1 = 1ili
& By performing image processing according to the processing conditions, it is possible to eliminate variations in the radiation energy level range recorded in the Mfi sheet on the sheet due to, for example, variations in the subject or irradiation area or variations in the amount of radiation exposure during individual image capture. However, it is possible to always obtain a visible image that is excellent in suitability for observation and interpretation, that is, in which always necessary subject image information is displayed in a density range suitable for observation and interpretation.

On the other hand, as is the case with the above system, when taking radiation images of the human body, it is generally necessary to avoid irradiating radiation to areas that are not necessary for humane diagnosis, or to avoid radiation to areas that are unnecessary for diagnosis. When a line is applied, scattered radiation enters the area necessary for diagnosis, reducing contrast resolution, so to prevent this, etc.
The radiation irradiation field may be narrowed down when recording radiation image information (at the time of imaging).

(Problem to be Solved by the Invention) However, when radiographic image information is captured with the irradiation field apertured as described above, the actual reading image signal read from the stimulable phosphor sheet, for example, the histogram of the image signal Even if image processing conditions are determined based on this, it is difficult to determine image processing conditions that are as favorable as one might have expected if they were determined in this way.

This is because when imaging is performed by narrowing down the radiation field of f)j-rays as described above, the scattered radiation generated from the subject in the radiation field usually enters the field of radiation on the stimulable phosphor sheet. Since the highly sensitive stimulable phosphor sheet also accumulates and records these scattered rays, the histogram of the actual reading image signal level also includes the image signal level based on this scattered ray, and as a result, the histogram of the actual reading image signal Even if the image processing conditions are determined based on the histogram of the image signal that carries the true image information within the irradiation field, it is determined based on the histogram that also includes the image signal (noise) based on scattered radiation. This is because there will be.

Therefore, when determining the image processing conditions based on the actual reading image signal as described above, if the image is being photographed with an irradiation field aperture, it is not determined simply based on the image signal itself obtained from the actual reading, but rather by some method. It is desirable to make the determination based on an image signal with less noise from which information due to the above-mentioned scattered radiation has been removed.

Problems in determining such image processing conditions occur not only in the case of imaging using the stimulable phosphor sheet mentioned above, but also in cases where radiation image information is generally recorded by applying an irradiation field aperture to the recording medium. This is something that can occur.

Note that the above-mentioned image processing conditions are a general term for various conditions that affect the relationship between the input and output of the image processing means, and include, for example, gradation processing conditions, spatial frequency processing conditions, etc. .

In view of the above-mentioned circumstances, an object of the present invention is to prevent scattered radiation information from being exposed outside the irradiation field when radiation image information is recorded on a recording medium such as a stimulable phosphor sheet with an irradiation field aperture. It is an object of the present invention to provide a method for determining image processing conditions based on the removed main reading image signal with less noise.

(Means for Solving the Problems) In order to achieve the above object, the method for determining image processing conditions according to the present invention uses a stimulable phosphor sheet, etc., on which radiation image information is photographed with the irradiation field apertured. Image data at each position on the recording medium is obtained from the actual reading image signal obtained by actual reading of the recording medium, this image data is subjected to differential processing, and the obtained differential value is used to determine the irradiation field on the recording medium. and determining image processing conditions based on the main reading image signal within this irradiation field.

Note that the term "recording medium" as used above refers to a medium capable of recording radiographic image information, and a specific example thereof includes the above-mentioned stimulable phosphor sheet, but is not necessarily limited thereto.

In addition, the above-mentioned "single reading image signal" refers to an image signal for visible image reproduction read from a recording medium as described above,
In the present invention, the main reading image signal used when determining the image processing conditions is the same as the image signal used for image processing.

In addition, the above-mentioned "determining the image processing conditions based on the main reading image signal within the irradiation field" refers to the case where the image processing conditions are determined based only on the image signal, as well as the case where the image processing condition is determined based on the image signal and other factors, such as the above-mentioned imaged part, etc. This meaning also includes cases where the decision is made based on the photographing method, etc.

Further, the image processing conditions may be determined in any manner as long as they are determined based on the main reading image signal within the irradiation field, that is, by using the main reading image signal within the irradiation field. One example is a method that uses the histogram of the actual reading image signal, but of course the method is not limited to this method.

Furthermore, the image processing conditions to be determined are typically gradation processing conditions, but are not necessarily limited thereto.

−15= Furthermore, the method of differentiation when differentiating the above image data is
It may be a -dimensional first-order differential or a higher-order differential, or it may be a two-dimensional first-order differential or a higher-order differential. Furthermore, in the case of discretely sampled images, differentiating is equivalent to finding the difference between adjacent image data. The method of differentiation, for example, how to find the difference between which image data, may be determined as appropriate, for example, depending on the individual algorithm that will be used subsequently to detect the irradiation field using the difference. Furthermore, "existing in the vicinity" is not limited to the case where the devices are adjacent to each other, but also includes, for example, the case where the devices are present every other time.

Note that in order to obtain image data at each position on the recording medium from the image signal, it is first necessary to set the position on the recording medium. This position may be set for each image, or a plurality of pixels having a certain relationship, for example, three to five pixels lined up in a certain direction, may be set as one position. In the former case, the image data at each position means the image signal of the pixel corresponding to that position, and in the latter case, the image data at each position means the image signal of the pixel corresponding to that position. Determined data, for example, image data obtained by averaging image signals of a plurality of pixels. This latter position setting means, in other words, that the image signal for each image obtained by reading is preprocessed by linear or nonlinear filtering, for example, the image information for each pixel is divided into 3 to 5 lines. It means one-dimensional smoothing. How to set the position, that is, what kind of preprocessing to perform, can be determined as appropriate depending on the differential processing to be performed later.
In short, any preprocessing may be used as long as it leaves necessary information such as irradiation field contour points and removes unnecessary information such as noise.

Further, the method of "irradiation field detection using differential values", that is, the algorithm for detecting the exposure field using differential values, is not limited to any particular method. The irradiation recognition method according to the present invention is based on the following method: [Since the level of the read image signal corresponds to the energy level of the radiation incident on the recording medium such as a stimulable phosphor sheet, the image signal outside the irradiation field generally has a low quantum level. , the image signal within the irradiation field will generally be at a high quantum level. Therefore, the system focuses on the fact that the difference (absolute value of the differential value) between image data in the part where the contour of the irradiation field is located is generally a larger quantum level than the difference between image data in other parts. If the irradiation field is to be detected using the characteristics of such differential values, for example, the differential values may be processed using an appropriate method, or other differential values may be calculated using an appropriate method. Any algorithm may be used, such as one that tracks things larger than the value.

(Effects of the Invention) As described above, the method according to the present invention obtains image data at each position on the recording medium from the main reading image signal, performs differential processing on this image data, and uses the obtained differential value to perform irradiation. The field is detected, and image processing conditions are determined based on the actual reading image signal within this field.

As mentioned above, the differential value of the part where the irradiation field contour is located is generally larger than the differential value of other parts, so based on such a differential value, for example, the differential value can be calculated using an appropriate method. The irradiation field can be detected accurately by tracking large differential values using a suitable method.

Therefore, even when the irradiation field is narrowed down, the method according to the present invention eliminates the adverse effects of scattered radiation outside the irradiation field on the recording medium, and the effective image signal within the irradiation field on the recording medium. Image processing conditions can be determined based solely on the above, and as a result, optimal reading conditions can always be determined.

In particular, the method according to the present invention directly detects the irradiation field based on the differential value obtained by differential processing the image data, that is, based on the image information recorded on the recording medium 1, and therefore accurately detects the irradiation field. It is possible to detect the irradiation field and therefore determine the optimal image processing conditions with higher accuracy.

In addition, if the main reading image signal for each pixel is preprocessed and then subjected to differential processing as described above, the preprocessing can eliminate the influence of noise contained in the image signal, and the subsequent processing Since the number of image data to be processed can be reduced, the irradiation field can be detected more accurately and at high speed.

By appropriately selecting an algorithm for detecting the irradiation field, the method according to the present invention can accurately detect the irradiation field not only when the shape of the irradiation field is rectangular but also when the shape is other than that, such as a circle. It can also be applied to detection.

(Example) Hereinafter, an example of the image processing condition determining method according to the present invention will be described with reference to the drawings.

First, a first example will be described.

The first embodiment is a method that can be applied when it is known in advance that the irradiation field is rectangular, and the X-axis is applied along two adjacent sides of the outline of the rectangular irradiation field.

Select the Y-axis, find the differential value in the X-axis direction (differentiate in the X-axis direction), aggregate this differential value in the Y-axis direction to determine the position of the above contour on the X-axis, and The irradiation field is detected by calculating the differential value in the direction (differentiating in the Y-axis direction) and totaling this differential value in the X-axis direction to determine the position of the above contour on the Y-axis. be.

In this example, when the irradiation field is rectangular, according to the above method, the aggregate of the differential value (absolute value of the differential value) of the part where each contour is located will be a much larger value than the aggregate of other places. This was done by focusing on the fact that

A specific example of this first embodiment will be described in detail below.

The specific example described below is to determine image processing conditions when imaging is performed with a rectangular irradiation field diaphragm as shown by the dashed line on the stimulable phosphor sheet 1, as shown in FIG. It's a method.

First, the X-axis and y@ are selected along the outline of the irradiation field 2 in FIG. 1, that is, along two adjacent sides of a rectangle indicated by a dashed line. Note that when the outline of the sheet 1 and the outline of the irradiation field 2 are parallel as shown in Fig. 1, the selected X-axis and y-axis
The axial direction corresponds to the main scanning direction and the sub-scanning direction in main reading.

Then, the position of the irradiation field outline 2a in the y-axis direction is determined as follows.

First, the above-mentioned sheet 1 is read, and the digital ii! ii Obtain image data. In this specific example, the actual reading image signal obtained by actual reading means each scanning point on the sheet 1 (i.e., each pixel ) refers to the electrical signal corresponding to the amount of stimulated luminescence for each period.

In this specific example, the digital electric signal f (×) for each pixel, which is the main reading image signal, is determined by the main reading.

y) (see Figure 2 (a)) and f(1, t).

f (2, t ), f (3, 1) -- are the lines lined up in the X-axis direction as the first line, f (1, 2>, f
(2゜2), f(3,2)... is the second line, and the same goes for the third line, fourth line, etc., and the above f(x , y) is preprocessed to one-dimensionally smooth every three lines to obtain digital image data F (x, y) at each position (second
(See figure (b)). That is, (f (s, + ) + f (t, 2 ) + f
(t, 3)/3 = r(t, 2) (f (2, 1>+f (2, 2>+f (2,
3>/3 =F (2, 2) (f (+, a) ten f (1, 5) + f (1,
6>/3 =F (+, s)(f
(2,4>10f (2,5>+f (2,8)/3
=F(2,5) and calculate the first. Second. The third line is one-dimensionally smoothed, and in the same manner, all f(x, y) are one-dimensionally smoothed three lines at a time to obtain digital image data F (x, y) at each position. Therefore, in this case, three pixels lined up in the y-axis direction are set as one position, and the digital image data at this position is f (×) at the three pixels.

y) is added and averaged.

It should be noted that the number of lines to be smoothed can be determined as appropriate, and if smoothing is to be performed every n lines, then F (x
, y) is expressed by the formula.

In this smoothing method, when calculating the edges (contours) of the irradiation field in the y-axis direction, the edges are averaged in the x-axis direction, so the edges are not blurred in the y-axis direction. Noise that interferes with extraction can be reduced, and calculations are simple and fast.

In this way, digital image data F (
After finding the image data F(x, V),
y). That is, the difference between the image data F (x, y) at nearby positions is determined. In this specific example, the difference Δ(X, V) between adjacent image data F(X, y) in the y-axis direction is calculated. (See Figure 2 (C)). That is, In(t,
2)-F(2,2)l-Δ(t, 2
)IF(2,2>-F(3,2>1-Δ(2,2
)IF(1,s) F(2,5>1 −△(1,
s ) IF (2, s) F (3, 11) l=
A differential process called Δ(2,s) is performed. The differential processing in this embodiment is not limited to finding the difference between adjacent image data; for example, image data F (1, 2) and F (3,
2) may also be a differential process that calculates the difference between 2) and 2).

Next, set an appropriate threshold TLI and set the above difference △(X
, l/) is greater than its threshold T, 11, then “1
”, otherwise rOJ as the difference Δ(×.

y) is binarized. By doing this, as shown in Figure 3 (
, l) can be obtained.

The above-mentioned smoothing and differentiation methods are just examples, and it goes without saying that a method that does not involve smoothing or a method that uses a Laplacian encyclopedia or the like as differentiation may also be used. However, the above method can perform calculations at high speed, and has a higher probability of extracting edges in the irradiation field than edges within the object (for example, bones).

Then, this binarized difference data Δ′(×.

y) in the y-axis direction, that is, Δ'(1, 2>+Δ'(t+5)+...
Δ' (2, 2 >10' (2, 5) 10...
Figure 3 (b ) is created, and the X coordinate whose frequency is greater than a predetermined threshold value 1-2 is determined to be the position of the irradiation field outline 2a in the y-axis direction.

If there is no X coordinate exceeding the threshold value TL2, it is determined that irradiation field narrowing has not been performed. Also,
When there is only one point to cross as shown in Figure 4(a),
The presentation level of the original f(x, y) is considered, and the one with the higher average quantum level (see FIG. 4(b)) is determined to be the irradiation field.

After finding the position of the irradiation field outline 2a in the y-axis direction (x position $J) as described above, next find the position (y coordinate) of the irradiation field outline 2b (see Figure 1) in the y-axis direction. However, the position of the contour 2b in the X-axis direction is also determined in the same manner as the position of the contour 2a in the y-axis direction.

That is, the position of the contour 2a in the y-axis direction is determined by smoothing arbitrary plural lines with f(x, y) arranged in the X-axis direction as one line, as described above, to determine the image data F (x, y), and calculate the adjacent F in the X-axis direction.
(x, y) The difference Δ(x, y) between the two is calculated, and Δ(x, y) is calculated in the y-axis direction. However, the position of the contour 2b in the X-axis direction is Image data F at each position is obtained by smoothing arbitrary multiple lines with the lined f(X, V) as one line.
(X, V) and adjacent F (x
, y) Find the difference Δ(x, y) between the two and calculate Δ(
X, V') is binarized using a predetermined threshold value TL1', this binarized data is aggregated in the X-axis direction, and the y-coordinate at which the frequency exceeds the predetermined threshold value TL2' is in the X-axis direction. It is determined that this is the position of the contour 2b.

If there is no point to be crossed or only one point to be crossed, the judgment is the same as for the contour 2a in the y-axis direction.When determining the position of the irradiation field contour 2b in the X-axis direction, the irradiation field contour 2b in the y-axis direction has already been Since the position of the field contour 2a has been determined, the image information f(x, y) within the radiation field contour 2a in the y-axis direction is
It is sufficient to perform the above-mentioned processing only for those areas, and by doing so, the detection speed of the irradiation field can be increased accordingly.

Once the irradiation field has been detected as described above, image processing conditions are determined from the main reading image information within the irradiation field. Any method may be used for this determination, but for example, as described above, a histogram of the main reading image signal within the irradiation field is obtained, and from that histogram, the maximum image signal level pmax and the minimum image signal level P of the desired image signal range are determined. min is determined, and tone processing conditions, which are one of the image processing conditions, are determined based on pmax and pmin.

This method will be explained in detail as follows. First, find the histogram of the reading image signal within the irradiation field,
The range of the desired image signal is determined from this histogram.

The desired image signal range is determined by the histogram pattern, which varies to some extent depending on the area to be imaged and the imaging method.
It is determined from the histogram with reference to these imaging areas and imaging methods. For example, the histogram for chest radiography has a pattern like this in Figure 5, where J is the mediastinal region,
Since we can know that K is the heart region, lung region, M is the skin and soft tissue, and N is the outside of the subject, from this histogram we can determine the maximum image signal level P max and the minimum image within the range of the desired image signal. The signal level p min can be determined. For example, in the case of FIG. 5, if information on the skin and soft parts M and the outside of the subject N is unnecessary, P max as shown including the desired image signal ranges J and KXL
to Pm1n. This p max and p
As a method for determining min, for example, a certain frequency threshold value T1. T2 is determined, and this T
1. One possible method is to obtain it using T2, but any other method may be used to obtain it from the histogram.

On the other hand, in a radiographic image information recording and reproducing system, as mentioned above, a main reading image signal is usually obtained from stimulated luminescence light by a photoelectric reading means, and this signal is subjected to gradation processing and other signal processing by an image processing means. The signal is reproduced and recorded as a visible output image on a photographic material or the like by an image reproduction means. In this output image, there is a density range suitable for observation and interpretation, and generally this appropriate density range (Dmax ~ Qm
in ) is predetermined, and the reproduction conditions of the image reproduction means (conditions that determine the relationship between the input to the reproduction means and the output from the reproduction means) are also predetermined, so that the appropriate density range (D max ~ [) min)
the input signal level range to the image reproduction means corresponding to (
Rmax to Rmin) are uniquely determined according to the image reproduction conditions.

Therefore, p max and Pm1n obtained as above
are R max and R min determined as above.
The gradation processing conditions in the gradation processing are determined so as to correspond to the gradation processing.

Gradation processing is a process in which each image signal input to an image processing means (gradation processing means) is output after converting its level according to certain conditions, and these certain conditions are called gradation processing conditions. , usually represented by a nonlinear tone curve.

The purpose of such gradation processing is to obtain a preferable visible output image suitable for diagnostic purposes depending on the imaging conditions such as the imaging region such as the head or chest and the imaging method such as simple or contrast imaging. , Generally, a basic form of nonlinear gradation processing conditions having the most preferable pattern for each imaging condition is determined in advance, and l! of each image is determined in advance. ! ! When performing i-tone processing, it is preferable to select an appropriate basic form of gradation processing conditions according to the photographing conditions of the image, and to perform gradation processing using this basic form.

In this specific example as well, an appropriate one is selected from among the basic shapes of gradation processing conditions predetermined according to the imaging conditions of the image, and it is modified based on the irradiation field white image signal. In other words, as shown in Fig. 5, the basic shape can be shifted vertically or
Pmax, Pm1n by rotating around
The gradation processing conditions to be positioned and used are determined so that, etc., correspond to R+nax, Rmin.

Note that the gradation processing conditions are not limited to the nonlinear ones determined by the shooting conditions as described above, but may also be linear ones. In that case, one predetermined straight line may be used as the above case. The gradation processing conditions to be used are determined by similarly rotating or shifting and positioning so that Pmax, Pm1n, etc. correspond to Rmax, Rmin.

The determination of gradation processing conditions by this method is not based on the imaging site or imaging method as in the former method, but is performed based only on the image signal within the irradiation field.

In this way, from the main reading image signal histogram, the above Pmax
, Pm1n, and determine the gradation processing conditions so that Pmax and pmin correspond to the above Rmax and Rmin, respectively, the image signal based on the scattered radiation outside the irradiation field is included in the actual reading image signal histogram. If you do so, the following inconveniences will occur.

That is, since the image signal level based on scattered radiation may be higher than the image signal level within the irradiation field, it is difficult to distinguish between the two from an image signal histogram that includes both. Therefore, when pmax and pmin are obtained from the histogram as described above and gradation processing conditions are determined from this, the minimum value of the image signal level within the irradiation field should be pmin, but the image signal due to the scattered radiation outside the irradiation field is A case may occur where the minimum value of the level is set to p min. In this way, when the minimum value of the image signal level outside the irradiation field is set to P min, that value is generally lower than the minimum value of the image signal level within the irradiation field, so it is unnecessary for diagnosis when reproducing visible images. Scattered radiation will be displayed in the low concentration area, so 1i of the image of the part necessary for diagnosis will be displayed.
If the ft degree becomes too high, the contrast will drop as a result, making it difficult to make a satisfactory diagnosis.

According to the above specific example, p
Since max and pmin are determined, such inconvenience can be eliminated.

In other words, if the gradation processing of the image signal is generally performed according to the gradation processing conditions set according to the image signal of each captured image, for example, the subject, the area to be captured, the radiation dose, etc. Even if the range of radiation energy level accumulated and recorded on each photographed sheet changes as a result, the necessary subject image information suitable for observation and interpretation is always present in any visible output image regardless of the fluctuation. This is advantageous because it can be displayed within an appropriate concentration range, but in particular, according to this embodiment, it can be determined based on the main reading image signal that does not include scattered radiation information noise, so that the necessary subject image information can be displayed. The effect of displaying within the appropriate density range is more pronounced.

Such a method of determining gradation processing conditions processes the read image signal based on the determined reading conditions without considering the fluctuations in the radiation energy level range recorded in each individual imaging as described above. It is useful if used in some cases.

After determining the image processing conditions, image processing is performed according to the determined image processing conditions. In this case, for example, the read actual reading image signal is temporarily stored in an appropriate storage means, and the aforementioned actual reading image signal is used to perform the above-mentioned irradiation field recognition and determination of image processing conditions, and then the actual reading image signal is stored from the storage means. All you have to do is read it out and subject it to image processing according to the image processing conditions.

In addition, in the method according to the present invention, a predetermined position is set on the recording medium as described above, and the difference between the image data at neighboring positions is calculated. If there is an outline of the irradiation field between the compared positions, the Focusing on the fact that the difference is a large value, this difference is used to determine the position of the irradiation field. In some cases, the difference can be determined from the difference itself, and in other cases, the difference may be large at the boundary between soft tissue and bone within the irradiation field, similar to the contour of the irradiation field, and it may be necessary to distinguish between the two. be. Various methods can be considered for discrimination in such a case, but for example, discrimination can be made by using the shape of the irradiation field that is known in advance, as in this first embodiment, and summing up the differences along the contour. can do.

In addition, in the above specific example, the case where one irradiation field 2 exists on one stimulable phosphor sheet 1 was dealt with, but for example, one sheet is divided into two sections and each section is irradiated. The present embodiment is also applicable to so-called divided photography in which photography is performed with the field aperture narrowed. That is, even in the case of divided imaging, if each section is considered as one sheet, one irradiation field will exist on that one sheet. Therefore, by obtaining information in advance that it is divided imaging, this embodiment It is sufficient to apply it to each category.

Next, a second embodiment of the present invention will be explained.

In each of the embodiments described below, only the J method of detecting the irradiation field on the recording medium using differential values will be explained, which is different from the first embodiment already explained. The method of "determining image processing conditions based on the main reading image signal" is the same as that in the first embodiment, so a description thereof will be omitted.

The irradiation field detection method in the second embodiment obtains image data at each position on the recording medium from the image signal obtained by main reading, performs differential processing on this image data, and in a differential image consisting of the obtained differential values, First, find an arbitrary position where the differential value is the maximum or a predetermined value or more and make this the first point of interest. Next, search for the position where the differential value is the maximum among the surrounding positions adjacent to this first point of interest. Set this as the second point of interest, and then search for the position with the maximum differential value among the surrounding positions adjacent to this second point of interest, excluding the previous point of interest, that is, the first point of interest. This is set as the third point of interest, and the process of searching for this third point of interest is repeated to find new points of interest one after another, and when a position adjacent to the first point of interest is found as a new point of interest, That is, the method is characterized in that when the points of interest are sequentially searched for using the above method and the first point of interest is returned, the inside of the closed curve formed by sequentially connecting the points of interest up to that point is recognized as the irradiation field.

d5, "surrounding position adjacent to the point of interest" in the above
does not necessarily mean all of the surrounding positions adjacent to the point of interest. For example, if the contour of the irradiation field is known in advance, a part of the position may be determined according to the shape of the contour.

Hereinafter, a specific example of the second embodiment will be described in detail with reference to the drawings.

The specific example described below is a method of detecting one irradiation field 2 in a stimulable phosphor sheet 1 which has one irradiation field 2 photographed with a rectangular irradiation field aperture, as shown in FIG. be.

First, a main reading image signal is read from the stimulable phosphor sheet 1 shown in FIG. 1 in the same manner as in the first embodiment.

Next, digital image data at each position on the sheet is obtained from the main reading image signal read as described above. In obtaining this digital image data, it may be obtained directly from the above-mentioned main reading image signal, or it may be obtained by subjecting the image signal to preprocessing such as spatial filter processing.

If it is determined directly, for example, the position on the sheet may be set in pixel units, and the actual reading image signal of the pixel corresponding to each position may be digitized and used as digital image data at that position.

When calculating by performing preprocessing such as spatial filtering,
For example, a plurality of pixels in a certain relationship are set together as one position, and based on the main reading image signal of the pixels included in this position, for example, they are averaged to calculate the digital image data of the position. Alternatively, the digit n on the sheet may be set in units of pixels, and the digital image data at the position may be calculated based on the main reading image signals of a plurality of pixels corresponding to the position and surrounding positions. good. Median filter processing can be cited as one of the latter calculation methods. This median filter processing refers to the median value (median value) of the image information (quantization level) of a predetermined pixel (position) and its surrounding pixels (position) as the image signal (image data) of that predetermined pixel (position). Processing.

An example of this median filter processing will be explained with reference to FIG. 6Q-. FIG. 6(a) is a diagram showing an original image 14 consisting of the main reading image signal for each pixel, and each square in the figure represents one pixel. FIG. 6(b) is a diagram showing a median filtered image 16 consisting of digital image data at each position obtained by performing the above median filtering on the image signal of each pixel in the original image. Note that in this specific example, the positions are set in pixel units, so each position in the processed image 16 is also referred to as a pixel.

First, a mask 18 of a predetermined size, for example, a 3×3 size mask 18 having a width of 3 pixels in the vertical and horizontal directions, is used, and the mask 18 is placed so that a predetermined pixel (the pixel indicated by diagonal lines in the figure) is located in the center of the mask. is placed in the original image 14, and the median value of the image signals of the nine pixels included in that mask is digitized as the digital image data of the predetermined pixel, and this processing is applied to the original image 14. Applies to all pixels (however, it cannot be applied to pixels located on the outermost periphery, so those pixels are excluded), obtains digital image data for that pixel, and performs median filter processing using this data. Image 16 is obtained. Note that if a 3×3 size mask is used, as described above (because the median filter processing cannot be applied to the outermost pixels, the processed image 16 will be 17 times smaller than the original image 14 by the outermost pixels). For example, this outermost pixel portion 17 has a quantization level of O (zero).
can be substituted as image data. The size of the mask is not limited to 3×3. In addition, the processed image 16
In order to prevent this from becoming small, for example, median filtering may be performed on the assumption that there are pixels around the original image 14 that have the same quantization level as the outermost pixels of the original image. By performing the above median filter processing, it is possible to remove noise when the quantization level is extremely high or low compared to surrounding pixels, and the advantage is that the irradiation field contour information is not blurred. be.

Note that the above preprocessing is not limited to the median filter processing described above, but can be any spatial filter processing that has the characteristics of leaving necessary information such as the contour of the irradiation field and removing unnecessary information such as noise. Anything is fine.

After obtaining digital image data at each position on the sheet as described above, the image data is then subjected to differential processing to create a differential image consisting of differential values.

Differential processing may be performed using any method.

FIGS. 7(a) and 7(b) are diagrams each showing a processed image, and each square in the diagram indicates one position.

For example, as shown in FIG. 7(a), when differentiating digital image data at a predetermined position 20 in a processed image 16, a mask 22 with a pixel size of 2×2 is used.
2 is placed so that the predetermined position 20 is located in the upper left part of the mask, and the digital image data of the four positions included in the mask 22 are as shown in the figure (a, b, c, d). Differential processing may be performed by performing a calculation, setting a' as a differential value at the predetermined position 20, and performing this differential calculation for each position.Furthermore, instead of the above formula, the following calculation is performed to perform differential processing. You can do it.

Of course, differential expressions other than these may be used.

Furthermore, although the above example is a first-order differential process, Fig. 7(b)
A mask 24 with a pixel size of 3×3 is used as shown in FIG. Like<a.

b, c, d, e, 19g, h, i, and performs the following calculation to set e' at the predetermined position 26.

Next, the contour of the irradiation field is detected based on the differential image created as described above. The above digital image data corresponds to the large serrations of the energy of the radiation incident on the sheet, so
Image data outside the irradiation field generally has a low quantum level;
Image data within the field will generally be at a high quantum level.

Therefore, the differential value of the image data at the position where the irradiation field contour exists generally has a larger quantum level than the differential value of the image data at other positions.

Therefore, in the differential image, the position where the differential value is maximum or the position where the differential value is greater than or equal to the predetermined value when the predetermined value is set appropriately can be recognized as the irradiation field contour, and there is only one irradiation field contour. Since it is formed by a closed curve of is larger than the differential values of other adjacent surrounding positions, in other words, it can be said that the irradiation field contour exists at least at the position where the differential value is the largest among the adjacent surrounding positions.

In this embodiment, based on the above facts, the irradiation field contour is detected by searching and tracking the positions where the irradiation field contour exists in the differential image one after another. It consists of two steps: a step of detecting a certain first point of interest, and a tracking step of tracking the position of the contour from the first point of interest.

First, the differential image is scanned to find an arbitrary position where the differential value is maximum or greater than a predetermined value, and this is set as the first point of interest.

As mentioned above, the differential value at the position where the irradiation field contour exists is larger than that at other positions. Therefore, if an appropriately set predetermined value is used, the position where the differential value is greater than or equal to the predetermined value will be the irradiation field contour. It can be determined that this is the position where the irradiation field contour exists, and of course it can also be determined that the position where the differential value is the maximum is the position where the irradiation field contour exists. Therefore, first, one of the irradiation field contour existing positions is determined by the method described above.
The first point of interest is detected and its position is set as the first point of interest.

Next, the irradiation field contour is tracked from this first point of interest,
Recognize the radiation field. This tracking first searches for the position with the maximum differential value among the surrounding positions adjacent to the first point of interest, sets this as the second point of interest, and then searches for the position in the surroundings adjacent to this second point of interest. Find the position where the differential value is maximum among the positions excluding the previous point of interest (the first point of interest) and set this as the third point of interest, and then repeat the process of searching for this third point of interest one after another. This is done by finding new points of interest. When a position adjacent to the first point of interest is found as a new point of interest, the inside of the closed curve connecting the previous points of interest is recognized as the irradiation field.

The above tracking can be performed using a mask as shown in FIGS. 8 and 9, for example.

The mask shown in FIG. 8 is a mask with a size of 3×3 pixels. For example, when tracking a rectangular irradiation field outline as shown in FIG. 10, as shown in FIG. The mask is arranged so that the first point of interest 8 existing on the irradiation field contour determined as above is located at the center of the mask (the shaded area in Fig. 8), and The position with the largest differential value among the positions (first point of interest A
) is set as the next point of interest, that is, the second point of interest B. Then, as shown in Figure 10 (b), move the mask so that the second point of interest B is located in the center of the mask, and The position with the highest differential value among the positions (the first and second points of interest,
Remove attention points A and B () to the next attention point, that is, the third attention point C
Then, in the same manner, new points of interest are sequentially searched for, such as the fourth point of interest D as shown in FIG. 10(C) and the fifth point of interest E as shown in FIG. 10(d), and As shown in , when a new nth point of interest F adjacent to the first point of interest A is found, the inside of the closed curve 30 connecting the first point of interest A to the nth point of interest F is recognized as the irradiation field 10. do. In addition, the first
The arrow in Figure 0 indicates the tracking direction of the irradiation field contour.

The mask shown in Fig. 9 covers all the surrounding pixels (8 pixels) adjacent to the pixel of interest, whereas the mask shown in Fig. 8 covers some of the surrounding pixels (4 pixels). This mask is configured to cover only pixels (pixels), and this mask is used by changing its orientation depending on the tracking direction. Note that the arrows in FIG. 9 indicate the tracking directions when using each mask.

A case will be described in which a rectangular radiation field is tracked using this mask.

First, if the differential image is scanned to find the position where the differential value is maximum and that position is set as the first point of interest A, then the 11th
As shown in Figure (a), there are four positions ■ adjacent to the first point of interest Δ in the x and y axis directions.

The position where the differential value is maximum is found among 'ir, m, and rv, and tracking is started from the first point of interest A in the direction of the position where the differential value is maximum. In the case shown in the figure, assuming that the differential value is at the maximum at the position (■), tracking is started in the left direction toward the position (■).

In this case, the tracking direction is to the left, so the tracking direction shown in Fig. 9 (
Using a mask oriented as shown in Figure 11(b), place the first mask on the diagonally shaded part of the mask.
Arrange so that the point of interest A exists, and the position with the largest differential value among the positions within the mask (excluding the first point of interest A)
Find it and set it as the next second point of interest B, then move the mask to position this second point of interest B in the shaded area of the mask, and in that state, select the most Find a position with a large differential value (excluding the previous points of interest 1st, 2nd points △, and B), make it the next 3rd point of interest, and repeat this process to find new points of interest one by one. . As shown in Fig. 11<b>, the tracking direction is left until the position of the upper left corner becomes the point of interest C, so the b part in the mask is always the maximum differential value position, and as long as that point, the tracking direction is to the left. Detection of the point of interest is continued using the mask shown in FIG. 9(a). However, the upper left corner position C
When we search for the point of interest, the lower part d has the maximum differential value. In this way, when the differential value of the portion d reaches the maximum in the mask of FIG. 9(a), detection of subsequent points of interest is continued using the mask of FIG. 9(b).

That is, in the manner shown in FIG. 11(C), the next point of interest E is detected by positioning the point of interest in the shaded area of the mask of FIG. 9(b). Then, until the position of the lower left corner reaches the point of interest, the tracking direction is downward, so the differential value is always at the maximum at section b in the mask, and as long as that is the case, use the mask shown in Figure 9 (b). Then, when the position of the lower left corner becomes the point of interest F, the d part in the mask will have the maximum differential value.
As shown in Fig. 1(d), continue detecting the point of interest in the same manner as above using the mask of Fig. 9(C), and when the position of the lower right corner becomes the point of interest G, next time, use the mask again in the same way. Since the differential value is maximum at the d part of When becomes the point of interest H, the d portion of the mask becomes the maximum differential value, so as shown in FIG. 11(f), the differential value in FIG. 9(a)
) continues to detect points of interest in the same manner as above, and when a position adjacent to the first point of interest A is found as a new point of interest I, it is located inside the closed curve 30 connecting the previous points of interest. is recognized as irradiation field 2. a3, the arrow in the figure indicates the tracking direction.

In the above example, the position of the maximum differential value in the differential image is
Although we have described the case where the point of interest is set as the first point of interest, if any point whose differential value is equal to or greater than a predetermined value is set as the first point of interest, tracking may be performed in the same manner as described above. However, when using the mask shown in Fig. 9, the mask used differs depending on the tracking direction, so it is necessary to determine the tracking direction.
As shown in FIG. 11<(+), the scanning direction (direction of arrow J) when searching for the first point of interest A may be set as the tracking direction, and a mask in that direction may be used initially.

Note that when O (zero) is assigned to the outermost pixel portion 17 in the processed image 16 as shown in FIG. 6(b) described above, even if the irradiation field is narrowed inside the stimulable phosphor sheet, Even if it is not, the differential value at the pixel in the outermost circumferential portion, which should essentially become the irradiation field contour, becomes large, and that pixel portion is detected as the irradiation field contour. Furthermore, if O (zero) is not assigned to the outermost pixel portion in the processed image as described above, a similar result can be obtained by performing differential processing assuming that O (zero) exists in the surrounding area.

Although the above specific example deals with the case of a rectangular irradiation field, the present embodiment is also applicable to the case of a circle or other non-rectangular irradiation field.

Further, in the above specific example, one stimulable phosphor sheet 1-F
Although the case where one irradiation field 2 exists in the first embodiment has been described, the present embodiment can also be applied to the case of so-called divided imaging, as in the case of the first embodiment.

In this embodiment, as described above, a differential image is created based on the main reading image signal, an arbitrary point in this image where the differential value is the maximum or a predetermined value or more is set as the first point of interest, and this first point of interest is Find the position with the maximum differential value from among the adjacent surrounding positions and set this as a new second point of interest.Thereafter, search for new points of interest one after another in the same way, and find the position adjacent to the first point of interest. When a new point of interest is found, the area inside the closed curve connecting the previous points of interest is recognized as the irradiation field.

As described above, in the differential image, the differential value at the position where the irradiation field contour exists is larger than that at other positions. Therefore, the above-mentioned first point of interest, which is an arbitrary position where the differential value is the maximum or more than a predetermined value set appropriately, is a position on the irradiation field contour, and among the surrounding positions adjacent to this first point of interest. Setting the position of the maximum differential value as the second point of interest, and repeating this method to find new points of interest one after another means sequentially tracking the positions on the contour of the irradiation field.

Therefore, according to this embodiment, it is possible to accurately recognize the irradiation field, and as a result, even when the irradiation field is narrowed down, the adverse effects of scattered radiation incident on the irradiation field on the sheet can be eliminated. However, since the reading conditions are determined based only on the effective image information within the irradiation field on the sheet, the optimum reading conditions can always be determined.

Next, a third embodiment of the present invention will be described.

The irradiation field detection method in the third embodiment obtains image data at each position on the recording medium from the image signal obtained by main reading, performs differential processing on this image data, and in a differential image consisting of the obtained differential values, First, find an arbitrary position where the differential value is the maximum or a predetermined value or more, make this the first point of interest, and then find a position where the differential value is greater than or equal to the predetermined value from among the surrounding positions adjacent to this first point of interest. Find this point and set it as a second point of interest, and then search for positions that are adjacent to the second point of interest, excluding the previous point of interest, that is, the first point of interest, and whose differential value is greater than or equal to a predetermined value. Search for a position and make this the third point of interest, and then repeat the process of searching for this third point of interest to find new points of interest one after another, and search for the position adjacent to the first point of interest as a new point of interest. When the point of interest is sequentially searched using the above method and the point of interest is returned to the first point of interest, the inside of the closed curve formed by sequentially connecting the points of interest up to that point is recognized as the irradiation field.

Note that the significance of "the surrounding position J adjacent to the point of interest" described above is the same as in the second embodiment.

Hereinafter, a specific example of the third embodiment will be described in detail with reference to the drawings.

The specific example described below is a method of detecting one irradiation field 2 in a stimulable phosphor sheet 1 which has one irradiation field 2 photographed with a rectangular irradiation field aperture, as shown in FIG. be.

First, the stimulable phosphor sheet 1 is actually read to read the actual reading image signal, image data at each position on the sheet 1 is obtained from this actual reading image signal, and this image data is subjected to differential processing, and the obtained differential value is Find the differential image. Since the method up to this point is the same as that of the second embodiment, detailed explanation will be omitted.

Similar to the second embodiment, the method according to the present embodiment detects the contour of the radiation field by finding and tracking the positions where the contour of the radiation field exists in the differential image one after another. , consists of two steps: a step of detecting a first point of interest, which is a tracking start point, and a tracking step of tracking the position of the contour from the first point of interest.

First, the differential image is scanned to find an arbitrary position where the differential value is maximum or greater than a predetermined value, and this is set as the first point of interest.

As mentioned above, the differential value at the position where the irradiation field contour exists is larger than that at other positions. Therefore, if an appropriately set predetermined value is used, the position where the differential value is greater than or equal to the predetermined value will be the irradiation field contour. It can be determined that this is the position where
Of course, the position where the differential value is maximum can also be determined to be the position where the irradiation field contour exists. Therefore, first, one of the positions where the irradiation field outline exists is detected by the method described above, and that position is set as the first point of interest.

Next, the irradiation field contour is tracked from this first point of interest,
Recognize the radiation field. This tracking first searches for a position whose differential value is greater than a predetermined value from among the surrounding positions adjacent to the first point of interest, sets this as the second point of interest, and then The process of searching for a position whose differential value is greater than or equal to a predetermined value and setting this as the third point of interest, and searching for this third point of interest from now on. This is done by repeatedly searching for new points of interest one after another.Then, when a position adjacent to the first point of interest is found as a new point of interest, the inside of the closed curve connecting the previous points of interest is irradiated. I recognize it as a field.

In the above tracking, if there is only one position whose differential value is equal to or greater than a predetermined value among the adjacent surrounding positions, that one position should be the next point of interest; if there are two or more, then is a certain priority given in advance to surrounding positions; The position with the maximum differential value may be set as an appropriate number of points of interest, and if there is none, the position with the largest differential value among the adjacent surrounding positions may be set as the next point of interest.

Of course, the position to become the next point of interest is selected from positions excluding the previous and current points of interest.

The above tracking can be performed using a mask as shown in FIG. 12 or FIG. 13, for example.

The mask shown in FIG. 12 is a mask with a 3×3 position size as shown, and an example of tracking performed using this mask will be described with reference to FIG. 14.

FIGS. 14(a) to 14(e) are diagrams each showing a differential image 28 having a rectangular irradiation field contour and sequentially explaining a method of tracking the contour.

First, as shown in Fig. 14(a), the first point of interest Δ existing on the irradiation field contour obtained as described above is located at the center of the mask (the shaded area in Fig. 12). The mask is arranged so that the mask is located, and the position within this mask where the differential value is greater than or equal to a predetermined value (excluding the first note point A, of course) is set as the next second note point. If the differential values of a plurality of positions are greater than or equal to a predetermined value, any of them may be selected as the second point of interest, but for example, the position with the maximum differential value among them may be selected. In the illustrated example, parts a and e of the mask correspond to the irradiation field contour positions, so the differential values of the positions of parts a and e are greater than a predetermined value, and the differential value of part e is larger, so is selected as the second point of interest B.

Next, as shown in FIG. 14(il), this second point of interest B
Move the mask so that it is located in the center, and similarly move the position in this mask where the differential value is greater than or equal to the predetermined value (of course excluding the current second point of interest B and the immediately preceding first point of interest A) to the next position. This is the third point to note. If the differential values of a plurality of positions are greater than or equal to a predetermined value, the position that is earliest in the priority order is set as the next third point of interest according to a predetermined priority order. There are various ways to give priority, but in this specific example, as shown in FIG. For example, if we call it part a, we move counterclockwise from part a.

Priorities are given in the order of c, d, e, f, g, and h. Therefore, in the example of FIG. 14(b), portions e and f of the portions that can become the new third point of interest have differential values greater than a predetermined value, and the position of portion e, which has the highest priority, is It has been selected as the third point of interest C.

Subsequently, in the same way, by setting the position where the differential value is above a predetermined value as a new point of interest, and if there are multiple positions where the differential value is above the predetermined value, the position with the earlier priority as described above is set as a new point of interest. As shown in Figures (C) and (d), the fourth point of interest D1 and the fifth point of interest E are selected, and new points of interest are successively selected in the same manner, as shown in Figure 14 (e). If the position adjacent to the first point of interest A is selected as the new lower point of interest, the inside of the closed curve 30 connecting the first point of interest A to the nth point of interest F is recognized as the irradiation field 2. .

Note that the arrow in FIG. 14 indicates the tracking direction of the irradiation field contour, and in this specific example, since the above-mentioned priority order is set in a counterclockwise direction, the tracking direction is also counterclockwise. However, the priority order may be set in a clockwise direction, in which case the tracking direction will also be clockwise.

The mask shown in Fig. 13 covers all positions (8 positions) surrounding the position of interest, whereas the mask shown in Fig. 12 covers only a portion (4 positions) of the surrounding positions.
It is configured to cover only the
This mask is used by changing its orientation depending on the tracking direction. Note that the arrows shown at the bottom of FIG. 13 indicate the tracking direction when using each mask.

A case will be described in which a rectangular radiation field is tracked using this mask.

First, determine the initial tracking direction. To do this, for example, if the differential image is scanned to find the position where the differential value is maximum and that position is set as the first point of interest 8, then as shown in Figure 15 (
As shown in a), there are four positions adjacent to the first point of interest A in the x and y axis directions.

The position with the maximum differential value is found among m, m, and rv, and tracking is started toward the first point of interest A or the position with the maximum differential value. In the case shown in the figure, assuming that the differential value is at the maximum at the position (■), tracking is started in the left direction toward the position (■).

In this case, since the tracking direction is to the left, a mask oriented as shown in FIG. Arrange the mask as shown in FIG. 15(b), find a position (excluding the first point of interest A) where the differential value is greater than or equal to a predetermined value among the positions in the mask, and move it to the next second point of interest. Point. In the illustrated example, only portion b of the mask has a differential value greater than or equal to the predetermined value, so the position of the corresponding portion is selected as the second point of interest B.

Next, as shown in FIG. 15(C), move this mask to position the second point of interest B in the shaded area of the mask, and in that state, the positional function value within the mask is set to a predetermined value. The above positions (excluding the previous points of interest 1st, 2nd points △, and B)
Find out and make that the third point of interest. In this case, in the illustrated example, part b and part 0 have differential values greater than a predetermined value, and the priority is a, as shown by the long arrow in FIG. 13(a).

Since they are assigned in the order of b, c, and d, the position of part b, which has the highest priority, is selected as the next third point of interest C.

Next, we will select the fourth point of interest, the second point of interest B.
Since the tracking from C to the third point of interest C is still in the left direction, similarly use the mask shown in FIG. While moving, the position shown in FIG. 15(d) is searched for a position where the differential value is greater than a predetermined value, and this is set as the next fourth point of interest. In the illustrated example, only portion d has a differential value greater than a predetermined value, and the position of portion d is selected as the fourth point of interest.

Next, we will select the fifth point of interest E, but since the tracking from the third point of interest C to the fourth point of interest is in the downward □ direction, we will use the mask in Figure 13(b). Move the mask so that the fourth point of interest is located in the shaded area of the mask, search for a position where the differential value is greater than a predetermined value in the state shown in FIG. 15(e), and use it as the next This is the fifth point to note. In the illustrated example, only portion b has a differential value greater than a predetermined value, and the position of portion b is selected as the fifth point of interest E.

Thereafter, new points of interest are sequentially searched for in the same manner, and when the lower left corner position is selected as a new point of interest F, a mask is placed as shown in FIG. 15(e) and the next point of interest is searched. be done. In this case, as shown in the figure, only the d part of the mask has a differential value greater than a predetermined value, and the position of the d part is selected as the next point of interest G, and when searching for the next point of interest, the tracking direction is changed. Therefore, use the mask shown in Fig. 13 <C>, and position the mask so that this point of interest G is located in the shaded area of the mask, that is, Fig. 15 (f
), and use the same method as above to move to the next point of interest H.
Select.

Thereafter, we continued to detect points of interest using the mask shown in FIG. 13(C) in the same way, and as shown in FIG. 15(f), the position of the lower right corner became a new point of interest ■. Then, the next point of interest J is the position of the d part of the mask, so the tracking direction changes upward, and the next point J is the position of the d part of the mask, as shown in Fig. 15 (g).
) as shown in Figure 7 (g). When the position of the upper right corner becomes a new point of interest, the next point of interest is again the d part of the mask. Therefore, the tracking direction changes to the left, and the tracking continues as shown in FIG. 15(h) (using the mask shown in FIG. 13<a>).

Then, as shown in FIG. 15(h), when the position adjacent to the first point of interest A is selected as the new nth point of interest M, the previous first point of interest 8 to the nth point of interest M are connected. The inside of the closed curve 30 is recognized as the irradiation field 2.

In the above specific example, it is assumed that in the corners of the irradiation field contour, there are multiple points in the mask where the differential value is greater than or equal to the predetermined value, and in the straight portion of the contour, there are only one point where the differential value is greater than or equal to the predetermined value.
We have proceeded with the discussion on the assumption that the point appears in the b part of the mask as mentioned above, but in any case, there is a possibility that multiple points with a differential value greater than or equal to a predetermined value will appear in the mask. In that case, the one with the highest priority -b, 3- is always the next point of interest. The next points of interest are a and b.
, when it appears in part c, the tracking direction remains the same and the mask used remains the same, and only when it appears in part d, it is sufficient to change the mask and continue tracking. Regarding this point, please refer to the 12th
The same applies when using the mask shown in the figure. however,
The mask shown in FIG. 12 differs from the mask shown in FIG. 13 in that the same mask is always used.

In the above example, the position of the maximum differential value in the differential image is
Although we have described the case where the point of interest is set as the first point of interest, if any point whose differential value is equal to or greater than a predetermined value is set as the first point of interest, tracking may be performed in the same manner as described above. However, when using the mask shown in Figure 13, the mask to be used differs depending on the tracking direction, so it is necessary to determine the tracking direction. The scanning direction (direction of arrow J) used when searching for the first point of interest A may be set as the tracking direction, and a mask in that direction may be used initially.

Although the above specific example deals with the case of a rectangular irradiation field, the present embodiment can also be applied to a case of a circle or other irradiation field other than a rectangle.

Furthermore, although the above specific example deals with the case where one irradiation field 2 exists on one stimulable phosphor sheet 1, this example deals with the case of so-called divided imaging as in the case of the first example. is also applicable.

In this embodiment, as described above, a differential image is created based on the main reading image signal, an arbitrary point in this image where the differential value is the maximum or a predetermined value or more is set as the first point of interest, and this first point of interest is Find a position whose differential value is greater than or equal to a predetermined value from among the adjacent surrounding positions and set this as a new second point of interest, and thereafter search for new points of interest one after another in the same manner and place them adjacent to the first point of interest. When a new point of interest is found, the area inside the closed curve connecting the previous points of interest is recognized as the irradiation field.

As described above, in the differential image, the differential value at the position where the irradiation field contour exists is larger than that at other positions. Therefore, the above-mentioned first point of interest, which is an arbitrary position where the differential value is the maximum or a predetermined value set appropriately, is a position on the irradiation field contour, and the surrounding area adjacent to the first point of interest of the octopus is the position on the irradiation field contour. Among the positions, the position where the differential value is equal to or greater than a predetermined value is set as the next second point of interest, and repeating this method to find new points of interest one after another means sequentially tracking the positions on the irradiation field contour. means.

Therefore, according to the method according to this embodiment, it is possible to accurately recognize the irradiation field, and as a result, even when the irradiation field is narrowed down, the scattered radiation incident on the irradiation field on the sheet Since the reading conditions are determined based only on the effective image information within the irradiation field on the sheet while eliminating adverse effects, the optimum reading conditions can always be determined.

Next, a fourth embodiment of the present invention will be described.

The irradiation field detection method in the fourth embodiment obtains image data at each position on the recording medium from the image signal obtained by main reading, performs differential processing on this image data, and generates a differential image consisting of differential values at each of the above positions. On the other hand, a multivalued image template having a portion corresponding to the irradiation field contour and in which each position in the irradiation field contour corresponding portion has a different value from each position in other portions, wherein the template corresponds to the irradiation field contour. We prepare a number of different templates depending on the shape and size of the irradiation field outline, and calculate the differential value on the above differential image or the differential value of this differential image. The present invention is characterized in that the correlation between the processed values and the values on each of the templates is calculated, and the inside of the portion corresponding to the irradiation field outline in the template with the highest correlation is recognized as the irradiation field.

Hereinafter, a specific example of the fourth embodiment will be described in detail with reference to the drawings.

The specific example described below is a method of detecting an irradiation field 2 when photographing a stimulable phosphor sheet 1 with a rectangular irradiation field diaphragm as shown by the dashed line, as shown in FIG. be.

In this method, first, digital image data at each position on the stimulable phosphor sheet is obtained from the main reading image signal obtained by the main reading similar to the first embodiment.

16/- Figure 16 is an enlarged view of a part of the upper left corner of the stimulable phosphor sheet in Figure 1. Each square in the figure represents one pixel, and each pixel f(1,
1), f(1, 2), ...... are each pixel (1, 1
), (1, 2), . . . shows the digitized version of the actual reading image signal.

In order to obtain digital image data at each position on the sheet from this image signal, it is first necessary to set the position on the sheet. The method of setting this position is not particularly limited as described above, but in this specific example, this position setting is performed pixel by pixel, and the digitized image signal of the pixel corresponding to each position is Digital image data.

As described above, digital image data at each position is obtained and the IC performs differential processing on this image data.

Although the method of differentiation is not particularly limited as described above, in this specific example, differentiation processing using two-dimensional differentiation is performed.

That is, first, the digital image data is differentiated one-dimensionally in the X direction, and the differential value δ' at each position is determined. This δ
' is equivalent to the image data difference between adjacent positions in the X direction, and is expressed as in the following equation.

δ'(1,1>=f(1,1)-f(1,2>δ'
(1,j>=t<1.2)-f(1,3)δ'
(2,1)=f(2,1)−f(2,2)δ' (
2,2)=f (2,2)−f (2,3) Then,
Similarly, one-dimensional linear differentiation is performed in the y direction to obtain the differential value δ'' at each position.This δ'' is calculated using the following formula% δl'(2,2>-f
) Then, based on the differential values δ′ and δ″ at each position in the one-dimensional first-order differential in both directions, for example, Gf both differential values δ
By adding the absolute values of ' and δ'', a two-dimensional differential value δ at each position is determined. This δ is expressed by the following formula.

δ(1,1)-16' (L 1) l++δ''(
1,1)1 δ (1,2)=l δ'(1,2>
l++ δ''(1,2>1 δ(2,1>=lδ'(2,1>l++δ''(2
,1)1 δ(2,2>=lδ'(2,2>l+1δ''(2
, 2) 1 By performing the above-described differential processing, the differential value δ at each position on the stimulable phosphor sheet is determined, and a differential image consisting of the differential value δ at each position is created. Note that in the above specific example, the differential value δ is always positive, but for example, when creating a differential image by -dimensional first-order differential processing, the differential calculated value may become negative depending on the position on the sheet. treats the absolute value of the calculated value as the differential value on the differential image. In addition, in the above specific example, a differential image is created using the obtained differential value δ itself, but in this example, the differential image is created by binarizing the differential value δ using a predetermined threshold value. It may be.

Once the differential image has been created, the differential image is correlated with a number of multivalued image templates prepared in advance, and the results are compared to detect the irradiation field.

FIGS. 18(a) to 18(l) show examples of a large number of multivalued image templates prepared in advance, and each template 4
2 is the area corresponding to the irradiation field contour (hatched area in the figure) 4
4, and at each position in the contour corresponding portion 44, for example, 1
For example, a value of 0 is assigned to each position in the other portion 46, and the shape and size of the portion 44 corresponding to the irradiation field contour of each template 42 is determined by the various irradiation field apertures that may be used for actual imaging. They differ depending on the shape and size of the irradiation field contour.

The size of the template 42 itself is preferably the same as the size of the stimulable phosphor sheet 1 (differential image);
It doesn't matter if they are different. The irradiation field contour corresponding portion 44 has a predetermined width t. This width t is determined by the nineteenth
．． As shown in FIG. 20, in addition to two positions or three positions, it may be one position or even four or more positions. The shape of the portion corresponding to the irradiation field contour is shown in Fig. 18(a).
Refers to the rectangle in (b), the circle in Figure 18 (c) and (d), etc.
Size refers to the length of one side of a rectangle, the diameter of a circle, etc.

Figures 18(e) and (f) show the 18th
Figure (q) shows a template that has a round aperture and has an irradiation field contour corresponding portion 44 that corresponds to the irradiation field contour in the case of divided imaging. Each position on the template 42 corresponds to each position on the differential image, but the correspondence does not necessarily have to be one-to-one; for example, one position on the template
One position may correspond to four positions adjacent to each other in the upper, lower, left, and right directions on the differential image. Each position in the irradiation field contour corresponding portion 44 is given a value of 1 or more,
For example, as shown in Fig. 19, one type of value, that is, only 1, may be assigned, or as shown in Fig. 20, two types of values may be assigned, that is, 2 in the center (1 on both sides). Of course, three or more types of values may be assigned, and the manner in which the multiple types of values are assigned may be determined as appropriate.

Next, the correlation between the differential image and the template image is determined. Here, taking a correlation means quantifying the degree of similarity between images by, for example, the following calculation. Then, the inside of the portion corresponding to the irradiation field contour of the template image that gives the maximum value is recognized as the irradiation field.

In other words, in this specific example, the differential value on the differential image (including both the differential value itself and the binary value) and the value on each template prepared above are multiplied for each position. and find the sum of the products. When a position on the differential image and a position on the template correspond in a pair, the values at the corresponding same position are multiplied, and for example, as mentioned above, the four positions on the differential image correspond to the positions on the template. When corresponding to one position, each differential value on the four positions is multiplied by the value on one position on the template.

Once the multiplication for each position is performed for the entire template, the various values are summed.

Then, such a summation of products is performed for each template, the results are compared, and the area inside the portion corresponding to the irradiation field contour of the template where the summation of products is maximum is recognized as the irradiation field.

In other words, the difference between image data in the part where the irradiation field contour is located is generally larger than the difference between the image data in other parts, so the differential of each position where the irradiation field outline is located on the differential image is The value becomes larger than the differential value at other positions, and as a result, the portion 14 corresponding to the irradiation field contour of the template
The sum of the above products in the case of a template in which the irradiation field contour is exactly located is naturally larger than the sum of the products in the case of a template in which this is not the case. Therefore, a large number of templates having corresponding parts to the irradiation field contour are prepared according to various shapes and sizes of the expected irradiation field contour, and the above-mentioned multiplication is performed between the differential image and each of these templates. If the sum of the products is compared and a template with the maximum sum is found, it means that the actual irradiation field contour exists in the irradiation field contour corresponding portion 44 of that template, and the inside of the contour corresponding portion 44 is found. (When the portion 44 has a certain width, the irradiation field may be any position within the portion 44, for example, the inner edge, outer edge, or center of the width portion). It can be recognized that

Note that if so-called split shooting is performed, the first
A template for divided imaging as shown in FIG. 8(g) may be used, or a template may be used for each segment of divided imaging to recognize the irradiation field.

In this embodiment, as described above, the main reading image data is subjected to differentiation processing to create a differential image consisting of differential values at each position, and a large number of templates as described above are prepared, and the differential value on the differential image or this differential value is The correlation between the processed value and the value on each template is calculated, and the inside of the portion corresponding to the irradiation field contour that falls on the template with the highest correlation is recognized as the irradiation field.

As mentioned above, the differential value of each position where the irradiation field contour exists on the differential image or the processed value thereof is larger than the differential value of other positions or the processed value thereof, so it is necessary to match the irradiation field contour of the template. In the case of a template in which the irradiation field contour is located in a part (for example, as described above, each position in this part is given a value of 1 or more, and other parts are given a value of O) Since the degree of similarity between a differential image and a template (for example, the sum of the products between the above-mentioned differential image and the template) is much larger than that of other templates, the irradiation field of the template with the highest degree of similarity is It can be recognized that the inside of the contour corresponding portion is the actual irradiation field.

Therefore, according to this embodiment as described above, even when the irradiation field is narrowed down, the adverse effects of scattered radiation incident on the irradiation field on the sheet can be eliminated, and effective image information within the irradiation field on the sheet can be Since the reading conditions are determined only based on this, it is possible to always determine the optimum reading conditions.

Next, a fifth embodiment of the present invention will be described.

The irradiation field detection method in the fifth embodiment obtains image data at each position on a recording medium from the image signal obtained by main reading, and defines each position lined up in a predetermined direction on the recording medium as one line. , the image data on the line is differentiated, and the absolute value of the differential value is a predetermined value T.
. The two positions exceeding the irradiation field contour candidate points on the line are determined, and the minimum value T1 of the image data on the line between the two candidate points is determined, and the image data on the line is the minimum value T1. Detecting two positions that exist on both sides of the field as irradiation field contour points on the line, performing detection of the irradiation field contour points for each line in a predetermined range on the recording medium, and It is characterized by recognizing the inside of the line connecting the irradiation field outline points on the line as the irradiation field.

A specific example of the fifth embodiment will be described in detail below with reference to the drawings.

The specific example described below is a method of detecting one irradiation field 12 in a stimulable phosphor sheet 10 which has one irradiation field 12 photographed with a rectangular irradiation field aperture, as shown in FIG. be.

First, the actual reading image signal is read from the stimulable phosphor sheet 10 shown in FIG. 1 by performing the actual reading similar to that in the first embodiment.

Next, digital image data at each position on the sheet is obtained from the image signals read as described above. To do this, you first need to set the position on the sheet.

The method of setting this position is not particularly limited as described above, but in this specific example, this position setting is performed pixel by pixel, and the digitized image signal of the pixel corresponding to each position is Digital image data.

−79= FIG. 22(a) is an enlarged view of the G section of the sheet 10 in FIG. f (1,
1), f (2, 1)...... are each pixel (1
, 1), (2, 1)..., the above-mentioned digital image data is shown. In addition, Fig. 22(b), (C
) will be explained later.

After the positions are set in this way and the digital image data at each position is obtained, each position aligned in a predetermined direction on the sheet 10 is then set as one line. This line may be set in only one direction or may be set in two directions. Of course, it may be set in more directions depending on the situation.

In this specific example, lines are set in the X-axis direction and the y-axis direction, which are orthogonal to each other. That is, each position (1,1>, (2,1>, (3°1), (4,1), (
5,1)...... is the first line LX in the X-axis direction
IN each position (1, 2>, (2, 2), (3, 2), (4
, 2), and <5.2) are set as the second line LX2 in the X-axis direction, and in the same manner, the third lines LX3,
A fourth line Lx, 4, ......... is set, and each position (1, 1), (1, 2) arranged in the y-axis direction is set.
), (1, 3>, (1°4)...... are the first line Ly1 in the y-axis direction, each position (2, 1>, (2, 2)
, (2, 3), (2, 4)... are set as the second line LV2 in the y@ direction, and the following y
Axial third line LVa, fourth line [y4,...
... is set.

Once the lines are set in this manner, a differential process or the like is performed on each line to detect the contour points of the irradiation field on the line. The method of detecting this irradiation field contour point will be explained by taking as an example the case of the n-th line 1-xn in the X-axis direction shown in FIG. 21.

FIG. 23 is a diagram showing the size of the digital image data at each position on the line 1-xn, and FIG. 24 is a diagram showing the size of the digital image data at each position on the line lxn obtained by differential processing. It is a figure showing a differential value.

First, the digital image data on the line 1-xn is subjected to differential processing to obtain the differential value δ at each position on the line.

Although the method of differentiation is not particularly limited as described above, in this specific example, first-order differentiation is performed to obtain the differential value δ for each position. As described above, this δ corresponds to the difference between image data at adjacent positions in the X-axis direction, and is expressed as in the following equation.

δ (1, n) = f (1, n) - f (2, n)
δ (2,n)=f (2,n>-f (3,n>
After obtaining the differential value δ at each position on the fourth line Lxn in this way, the absolute value of the differential value is then set to the predetermined value To.
The two positions Δ1S3i which are above are defined by the line 1-xn
The upper irradiation field contour candidate point is set as the upper irradiation field outline candidate point (see Fig. 24).

As described above, the difference (differential value) between image data in a portion where the outline of the irradiation field exists is generally at a larger quantum level than the difference (differential value) between image data in other portions. Therefore, the differential value is the predetermined value T.

It can be determined that the above position is a point where the outline of the irradiation field exists, and as a result, that point is selected as a candidate point for the irradiation field outline. In addition, since the irradiation field contour is generally a closed curve, one line intersects with the closed curve contour at two points.Therefore, there are two contour points on one line, and as a result, the contour candidate point is Two are also detected.

Next, the minimum value T1 of the digital image data on the line 1-xn between the contour candidate points A153i is determined.

In this specific example, as shown in FIG.
The minimum digital image data T1 between 1 and Bi is below the image data at one candidate point position Ai, but in some cases, as shown in FIG.
It is also conceivable that the image data Tc at the position C1 between 3i and other than the positions fili2Ai and 3i becomes the minimum value TI.

After finding the minimum value T1 in this way, the above line [xn
In the above, the two positions where the digital image data has the minimum value T1 and which exist on both sides are detected as the irradiation field contour points [)i and Ei on xn, in other words. Digital image data has this minimum value T
A position (Di-Ei) that is 1 or more is determined to be the irradiation field range on line lxn.

In this specific example, since the digital image data T^ at one contour candidate point position A1 has the minimum value T1, there are two positions where the digital image data has the minimum value T1 as shown in the figure.
Therefore, the two positions 1) iSEi automatically become the two positions that exist on the left and right outside. However, as mentioned above, if the digital image data Tc at the position Ci between A113i and other than Ai and [3i is the minimum value T1, for example, the position where the image data has the minimum value on the line 1-xn is the As shown in FIG. 5, three points, Di, Ci, and Ei, are detected, and in this case, two positions Di and Ei, which are located on both the left and right sides excluding Ci, are detected as contour point positions.

In addition, in this way, the contour imaginary position 1) i, Ei is calculated based on the minimum value TI of the image data between the contour candidate points Ai and Ei.
By detecting the irradiation field, the detected irradiation field can be made relatively wide, and as a result, it is possible to reduce the possibility that the detected irradiation field will be narrower than the actual irradiation field.

Then, the work of detecting the irradiation field contour points on one line as described above is performed for each line Lx in the X-axis direction over the entire area in the y-axis direction, and each line
By connecting the upper irradiation field contour points, contour lines 12a and 12b of the irradiation field 12 in the y-axis direction are obtained.

Next, the irradiation field contour points on any line 1jln in the y-axis direction are detected in the same manner as above, and the contour points are detected over the entire area in the X-axis direction for each line LV in the y-axis direction. Do, each line L
A contour line 12c in the X-axis direction connecting the contour points on y, 1
2d, and the area inside these contour lines 12a, 12b and the above-mentioned contour lines 12c, 12d, that is, the range surrounded by these contour lines, is recognized as the irradiation field 12.

The detection of the contour points may be performed for each line within a predetermined range on the sheet 10. That is, on the integral side of the tool 84, this is performed for each line over the entire range on the sheet 10, but for example, if the range where the irradiation field exists is known to some extent, it is performed only for each line within that range, or as described above. First, contour point detection is performed on the line L× in the X-axis direction, and the contour line 12a in the y-axis direction is
, 12b, the next line Ly in the y-axis direction may be determined only for the line Ly existing between both contour lines 12a and 112b.

In addition, although the above specific example deals with the case of a rectangular irradiation field,
This embodiment is applicable even to the case of an irradiation field other than a circle or a rectangle.

Furthermore, although the above specific example deals with the case where one irradiation field 12 exists on one stimulable phosphor sheet 10, it can also be applied to the case of so-called divided imaging, as in the case of the first embodiment. be.

Further, in the above specific example, contour point detection is performed for each of the lines in the X-axis direction and the y-axis direction, but it is not necessarily necessary to perform the detection for lines in two directions. For example, if the irradiation field shape is a circle or a diagonal rectangle as shown in FIGS. 26(a) and 26(b), the entire irradiation field contour can be detected by only detecting contour points for each line in the X-axis direction. It is something that can be detected.

Furthermore, in the above specific example, the digital image data was obtained by setting the position on the sheet 10 pixel by pixel, but the digital image data was obtained by devising the position setting as follows, and the irradiation field was detected based on it. You may also do this.

For example, if you know in advance that the irradiation field is rectangular,
Select the y-axis and y-axis along the two adjacent sides of the rectangle,
First, one position is set for every three pixels lined up in the y-axis direction, that is, position (1, 2)' = three pixels (1, 1) + (1
,2)+(1,3) Position(2,2)'-3 pixels(2,1)+(2
,2) + (2,3) position (1,5) ′=3 pixels (1,4) + (1
, 5) + (1, 6) position (2, 5) ” = 3 pixels (2, 4) + (
2, 5) + (2, 6), and calculate the digital image data F at each position using the following formula, F (1, 2) -= (f (1, 1) + f (1
,2) +f(1,3) ) /3 F (2,2) −= (f (2,1) +f <
2.2) +f(2,3) ) /3 F (1,5) −= (f (1,4) +f (1
,5) +f(1,6) ) /3 F (2,5) −= (f (2,4) +f (2
, 5) +f(2,6) ) /3 This image data F is differentiated for each line in the X-axis direction to obtain the differential value δ at each position as shown in FIG. The value δ is used to detect the irradiation field contour line in the y-axis direction in the same manner as described above, and then 3 lines aligned in the x-axis direction are detected.
Set one position for each pixel, that is, set each position as follows, position (2,1)' = three pixels (1,
1) + (2,1) + (3,1) position (2,2) ′=3 pixels (1,2) + (2
,2)+,(3,2)Position(5,1)'=3 pixels(4,1)+(5
,1) + (6,1) position (5,2) = =3 pixels (4,2) + (
5, 2) + (6, 2) The digital image data F at each position is converted to the position (1, 2)
) - 1 (2, 2) - . . . in the same way as in the case of The irradiation field contour line in the X-axis direction may be detected using the value δ in the same manner as described above.

Setting the position in this way means preprocessing the pre-read image information for each pixel before performing subsequent differential processing, etc. By performing this preprocessing, noise contained in the image information can be reduced. Since the influence can be eliminated and the number of image data to be processed thereafter can be reduced, the contour of the irradiation field can be detected more accurately and at high speed. Of course, the mode of pretreatment can be determined as appropriate.

In this embodiment, as described above, image data is differentiated for each line in a predetermined direction, and in each line, the minimum value of the image data between two positions where the absolute value of the differential value exceeds a predetermined value To T1 is determined, and the two positions where the image data is the same as its minimum value T1 and which exist on both sides are taken as the irradiation field contour points on the line, and the points on each line determined in this way are A contour line is obtained by connecting contour points, and the area inside the contour line is recognized as the irradiation field.

Therefore, according to this embodiment, even when the irradiation field is narrowed down, the adverse effects of scattered radiation incident on the irradiation field on the sheet can be eliminated, and based only on the effective image information within the irradiation field on the sheet. Since the reading conditions are determined based on the reading conditions, the optimum reading conditions can always be determined.

In addition, in this embodiment, two points whose differential value exceeds a predetermined value To are not recognized as contour points as they are, but are treated as contour candidate points, and a position that is equal to or greater than the minimum image data between these two contour candidate points is irradiated. Since it is determined that the irradiation field is within the field, it is possible to reduce the possibility that the irradiation field detected by this embodiment will be smaller than the actual irradiation field.

Next, a sixth embodiment of the present invention will be described.

The irradiation field detection method used in the sixth embodiment is to obtain image data at each position on the recording medium from the image signal obtained by main reading, and to detect image data at each position on the recording medium in a line in a predetermined direction. The image data on the line is differentiated, and the position where the absolute value of the differential value exceeds a predetermined value To is defined as a candidate point on the line for the irradiation field outline. Obtain the image data and calculate the characteristic value T of the image data from the image data.
h is determined, the position where the image data has its characteristic value Th on the line is detected as an irradiation field contour point on that line, and the detection of the irradiation field contour point is performed on each line in a predetermined range on the recording medium. The method is characterized in that the inside of the line connecting the contour points of the irradiation field on each line is recognized as the irradiation field.

Hereinafter, a specific example of the sixth embodiment will be explained in detail with reference to the drawings.

The specific example described below is the case where one stimulable phosphor sheet 50 is divided into two sections and a rectangular irradiation field is apertured for each section, as shown in Fig. 27. This is a method of detecting two irradiation fields 52 and 54.

First, the image signal Ml obtained from the above-mentioned reading
- Obtain digital image data at each position on the stimulable phosphor sheet from red, define each position lined up in a predetermined direction as one line on this sheet, and perform differential processing on the image data on the line.

The method up to this point in this embodiment is the same as that in the fifth embodiment, and the method up to this point in this specific example is completely the same as the specific example of the fifth embodiment, so a detailed explanation thereof will be omitted.

Note that section G in FIG. 27 according to this specific example is similar to section G in FIG. 21 according to the fifth embodiment, and when enlarged, it becomes as shown in FIG. 22(a).

Similar to the specific example in the fifth embodiment, positions are set in pixel units to obtain digital image data at each position, and then in the X-axis direction, the first line L x 1, the second line L x 2, etc.
... and the first line Ly1 in the Y-axis direction.
, second line L'l'2, . This method of detecting the contour points of the irradiation field will be explained by taking as an example the case of the first line L×1 in the X-axis direction shown in FIG. 27.

FIG. 28 is a diagram showing the size of the digital image data at each position on the line 1-xn, and FIG. 29 is a diagram showing the size of the digital image data at each position on the line lxn obtained by differential processing. It is a figure showing a differential value.

After calculating the differential value δ at each position on the n-th line 1-xn in the same manner as in the fifth embodiment, the positions A and C where the absolute value of the differential value is greater than or equal to the predetermined value To are next determined.

Let D be the irradiation field contour candidate point on the line lxn.

As described above, the difference (differential value) between image data in a portion where the outline of the irradiation field exists is generally at a larger quantum level than the difference (differential value) between image data in other portions. Therefore, a position where the differential value is a predetermined value of 10 or more can be determined to be a point where the outline of the irradiation field exists, and as a result, that point is selected as a candidate point for the irradiation field outline.

However, even if it is possible to determine that a position where the differential value is greater than or equal to the predetermined value To is a point where an irradiation field contour exists, the differential value of the point where the contour exists is not necessarily below the predetermined value. It does not necessarily exceed. That is, for example, the left irradiation field 52 in this specific example
Although there is a contour line such as the right side contour line 52b, the image data changes slowly (see FIG. 28), and as a result, as shown in FIG. 29, the right side contour line 52b
There may be a case where the differential value of the position B does not exceed the predetermined value To even though b exists at the position.

Therefore, it is not always possible to find the contour points of the irradiation field only by performing differential processing on the image data and subjecting the differential value to threshold processing. Therefore, in this embodiment, in order to find all contour points even in such a case, the following processing is further performed.

First, the line l at contour candidate points A, C, and D found by threshold processing using the predetermined value To.
The digital image data TΔ, Tc, and TD on xn are obtained (see FIG. 28). Next, these image data T△
, Tc, To, the characteristic value Th of the digital image data T^, Tc, To is determined.

The characteristic value Th may be any value as long as it is based on the image data T^, Tc, To, but for example, Th, Tc
, To can be the minimum value, average value, median value, maximum value, etc., as the characteristic value. In this specific example, Th, Tc, T
Th, which is the minimum value among o, is adopted as the characteristic value Th. In this way, if the minimum value is the characteristic value Th, then 1. The finally detected irradiation field can be made relatively wide, and as a result, the possibility that the detected irradiation field will be narrower than the actual irradiation field can be reduced.

After determining the characteristic value Th, as shown in FIG.
Determine C' and D' and set the positions on the above line 1-x.
Detected as an irradiation field contour point on n, in other words, a position where digital image data is greater than or equal to this characteristic value Th
Δ'~B'', C-~D') is determined to be the irradiation field range on line 1-xn.

Then, the work of detecting the irradiation field contour points on one line is performed for each line L× in the X-axis direction.
The contour lines 52a, 52b of the left and right radiation fields 52.54 in the y-axis direction are formed by connecting the radiation field contour points on each line Lx over the entire axial direction.

Find 54a and 54b.

Next, for any line L yn in the y-axis direction, the irradiation field contour points on the line are detected in the same manner as above, and the detection of these contour points is carried out on the X-axis for each line L'/ in the y-axis direction. The outline points on each line Ly are connected to form a contour line 52c in the X-axis direction,
52d, 54c, and 54d are determined, and the area inside these contour lines 52c, 52d, 54c, and 54d and the contour lines 52a, 52b, 54a, and 54b, that is, the range surrounded by these contour lines is recognized as the irradiation field.

The detection of the contour points may be performed for each line within a predetermined range on the sheet 50. That is, in the above specific example, the process is performed for each line over the entire range on the sheet 50, but for example, if the range in which the irradiation field exists is known to some extent, the process is performed only for each line within that range, or as described above, the X Contour point detection is performed for the line L× in the axial direction, and the contour line positions A-, B'', C- in the y-axis direction are detected.
, D-, the next line LM in the y-axis direction may be determined only for lines 8- to B- and C' to D'.

The above specific example was an example in which the position of one contour line 52b could not be determined only by the differential processing of the image data and the threshold processing of the differential value. This method can also be used even when all contour positions can be determined only by threshold processing. In the case of the method of determining contour line positions by differentiation and threshold processing, it is necessary to judge whether all contour line positions were detected by the method, and if there are contour lines that have not been detected, further Although some processing must be performed to detect the contour line, and the algorithm leading to the final irradiation field detection is complicated, the method according to this embodiment requires initial differentiation and threshold processing. Regardless of whether all contour line positions were detected with
This method has the advantage that all outline positions can be automatically detected at all times, and the algorithm is simple. Although the above specific example deals with a rectangular irradiation field, the present embodiment can also recognize an irradiation field other than a circle or a rectangle.

Further, although the above specific example deals with the case where there are two irradiation fields due to divided imaging, the present embodiment is also applicable to a case where there is only one irradiation field. Note that in that case, for example, there are only two contour lines in the y-axis direction, so there may be a case where there is only one contour candidate point obtained by the threshold processing. In that case, there is only one piece of digital image data at the outline candidate point, and in that case, for example, that image data itself may be used as the characteristic value Th.

Further, in the above specific example, contour point detection is performed for each of the lines in the X-axis direction and the y-axis direction, but it is not necessarily necessary to perform the detection for lines in two directions. For example, if the irradiation field shape is a circle or a diagonal rectangle as shown in FIGS. 26(a) and 26(b) in the fifth embodiment, the X
The entire irradiation field contour can be detected only by detecting contour points for each line LX in the axial direction.

Furthermore, in the above specific example, the digital image data was obtained by setting the position on the sheet 50 pixel by pixel, but for example, when it is known in advance that the irradiation field is rectangular, multiple pixels in a certain relationship may be set. They may all be placed in one position. In this case, position setting, calculation of digital image data at each position, and differentiation may be performed in the same manner as described using FIGS. 22(b) and 22(C) in the fifth embodiment, for example.

As described above, in this embodiment, image data is differentiated for each line in a predetermined direction, the image data at a position where the differential value exceeds a predetermined value To is obtained, and characteristic values are obtained from the image data. The position where the image data is the same as its characteristic value is defined as the irradiation field contour point on each line, the contour points are connected to obtain a contour line, and the area inside the contour line is recognized as the irradiation field.

Therefore, according to this embodiment, even when the irradiation field is narrowed down, the adverse effects of scattered radiation incident on the irradiation field on the sheet can be eliminated, and based only on the effective image information within the irradiation field on the sheet. Since the reading conditions are determined based on the reading conditions, the optimum reading conditions can always be determined.

Furthermore, as described above, this embodiment can detect the irradiation field contour that cannot be detected only by differentiation and threshold processing, and the irradiation field contour detection algorithm is relatively simple. has advantages.

Next, a seventh embodiment of the present invention will be described.

The irradiation field detection method in the seventh embodiment is to obtain image data at each position on a recording medium from the image signal obtained by main reading, and to define each position lined up in a predetermined direction on the recording medium as one line. , differentiate the image data on the line, and set the absolute value of the differential value to a predetermined value T.
The absolute value is below the predetermined value after threshold processing with o. Detect the position exceeding the line as a visible radiation field contour point, obtain the image data at the visible radiation field contour point, obtain the characteristic value Th of the image data from the image data, and calculate the above on the line. Image data or the above characteristic value T
h, a position other than the position that is the same as or in the vicinity of the manifest radiation field contour point is detected as a potential radiation field contour point, and the detection of the manifest and potential radiation field contour points is performed on the recording medium. This is performed for each line in a predetermined range, and the area inside the line connecting the actual and potential irradiation field outline points on each line is recognized as the irradiation field.

That is, in this embodiment, for example, if there are four contour points on the predetermined line, but only three of them can be detected by the differentiation and threshold processing, the three contour points are The characteristic value Th of the image data, for example, the minimum image data value Th among them, is determined from the image data at the position of these three visible contour points, and the image data value on the above line is determined as the characteristic value Th. A position that has a value Th and is not the same as or in the vicinity of the manifest contour point positions in the three examples above, in other words, a position that does not correspond to the three manifest contour point positions described above is considered a potential contour point. The irradiation field is recognized using these apparent contour points and latent contour points.

Similar to the sixth embodiment, this embodiment deals with the case where all contour points on a predetermined line cannot be detected by differentiation and threshold processing, and basically the sixth embodiment
This is similar to the example.

The difference between this embodiment and the sixth embodiment is that in the sixth embodiment, the position corresponding to the contour point detected by differentiation and threshold processing is set as a contour candidate point, and the characteristic value Th of the image data of this candidate point is While all contour points are detected, in this embodiment, positions corresponding to contour points detected by differentiation and threshold processing are recognized as actual contour points (not contour candidate points), This apparent contour point (6th
Characteristic value Th of the image data of the contour candidate point in the example
Therefore, only the contour points (and latent contour points) that were not detected in the differentiation and threshold processing are detected.

That is, to explain the reading side of this embodiment with reference to FIGS. Digital image data at each position on the sheet 50 is obtained from the signal, and the X-axis and Y-axis are
Each position aligned in the axial direction is defined as one line, and the image data on each line is first differentiated. And now,
It is assumed that the digital image data and the differential value of the data at each position on the line lxn in the X-axis direction are as shown in FIGS. 28 and 29.

In the sixth embodiment, as described above, the differential value is subjected to threshold processing using the predetermined value TO, so that the differential value is T. The above three points A, C, D
is a contour candidate point, and the image data T^ at that candidate point is
, Tc, ``ro'', and calculate the characteristic values Th of the points A', B', C', where the image data is Th.
D' was recognized as a contour point and the irradiation field was detected using them, but in this example, the above A, C, and D
is recognized as the manifest contour point -1 ('+A - ), the characteristic value Th is obtained from the image data at A, C, and D in the same manner as in the sixth embodiment, and the above-mentioned differentiation and threshold are calculated using this characteristic value Th. Only the position B where contour points that could not be detected by value processing should exist is set using this characteristic value T.
In other words, the image data is determined using this characteristic value Th
And the above A.

Positions that do not correspond to C and D are recognized as latent contour points B', and the irradiation field is detected from these manifest contour points A, C, and D and latent contour points B'.

Although the embodiments of the present invention have been described above, the present invention can be modified in various ways without departing from the gist thereof, and is not limited to the embodiments described above.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the stimulable phosphor sheet and the irradiation field in the first to fourth embodiments, and FIGS. 2 to 4 are diagrams for explaining the first embodiment. Figure 2(a) is a diagram showing the image signal for each pixel;
b) is a diagram showing image data at each position obtained from the image signal of each pixel, Figure 2 (C)
Figure 3(a) shows the difference data obtained by binarizing the difference in Figure 2(C). Figure 3(b) is a diagram showing a histogram obtained by aggregating the difference data in Figure 3(a), Figure 4(a) is a histogram in a different state from Figure 3(b). 4(b) is a diagram showing the quantum level of image information for each pixel when the histogram of FIG. 4(a) is obtained. FIG. 5 is a diagram showing the quantum level of image information for each pixel when the histogram of FIG. 4(a) is obtained. Figures 6 and 7 are diagrams showing an example of a method for determining gradation processing conditions in an example.
．． FIGS. 8 to 11 are diagrams for explaining the second embodiment, and FIG. Figure 6 (b) is a diagram showing a processed image obtained by median filtering the original image; Figures 7 (a) and (b) are diagrams each showing the position in the processed image and the mask used when performing differential processing; Figures 8 and 9 (a) to (d) are diagrams showing masks used when searching for new points of interest, and Figure 10 (a).
- (e) are explanatory diagrams of the method of finding new points of interest using the mask shown in Fig. 8, and Figs.
12 to 15 are diagrams for explaining the third embodiment; Figures 13 (a) to (d) are diagrams showing masks used when searching for new points of interest, and Figure 14 (
a) to (e) are explanatory diagrams of a method for finding new points of interest using the mask shown in FIG. 12, and FIG. 15 (a) to (i)
) is an explanatory diagram of a method of finding a new point of interest using the masks shown in FIGS. 13(a) to (d), and FIGS. 16 to 20 are diagrams for explaining the fourth embodiment, FIG. 16 is a partially enlarged view of the upper left corner in FIG.
17 is a diagram showing image data at each position, and FIG. 17 is a diagram showing a part of a differential image. FIG. 17(a) is a differential image obtained by one-dimensional first differentiation in the X direction, and FIG. A differential image obtained by one-dimensional first-order differentiation in the direction, Fig. 17 (C) is x, y
18(a) to (9) are diagrams each showing an example of a multi-valued image template. Partially enlarged views, Figures 21.23 to 25 are diagrams for explaining the fifth embodiment, Figures 22.26 are diagrams for explaining the fifth to seventh embodiments, and Figure 21 is a diagram for explaining the stimulable phosphor sheet and irradiation. Figure 22 (a)
) is an enlarged view of part G in Figure 21, Figure 22 (b) is a diagram showing image data at each position, Figure 22 (C) is a diagram showing differential values at each position, and Figure 22 (C) is a diagram showing differential values at each position.
3 is a diagram showing image data on line lxn, FIG. 24 is a diagram showing differential values of image data on line lxn, FIG. 25 is a diagram showing other image data on line 1-xn, and FIG. 26 is a diagram showing image data on line lxn. Figure (a) shows Sea 1- where circular irradiation field aperture was performed.
26(b) is a diagram showing a sheet in which the diagonal rectangular irradiation field diaphragm has been damaged, FIGS. 27 to 29 are diagrams for explaining the 6.7th embodiment, and FIG. Diagram showing the fluorescent phosphor sheet and the irradiation field, 2nd
FIG. 8 is a diagram showing the image data on the line xn, and FIG. 29 is a diagram showing the differential value of the image data on the line 1-Xn. 1, 10.50... stimulable phosphor sheet (recording medium) 2, 12.52.54... irradiation field 2a, 2b
, 12a, 12b, 12c, 12d,
52a, 52b. 52c, 52(+, 54a, 54b,
54c, 54d...Irradiation field contour 14...Original image 16...Processed image 28
...Differential image 30...Closed curve 42.
...Multi-valued image template 44...Irradiation field contour corresponding part 46...Other parts No. 6 (b) 1985 O Takutsu (+2/day 1988 Patent Application No. 015.456 2, Invention Name of Image Processing Condition Determination Block 3, Relationship with the Amendment Person Case Name of Patent Applicant Address 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Name (
520) Fuji Photo Film Co., Ltd. Representative Ohnishi
Fact 4. Agent address: 7th floor, Uraiya Building, 5-2-1 Roppongi, Minato-ku, Tokyo. Subject of correction: Drawing 7. Contents of correction: The hand-drawn drawing will be corrected to an inked drawing. (No change in content)

Claims (12)

[Claims] (1) Image when performing main reading in which an image signal for visible image reproduction is read from a recording medium on which radiation image information is recorded by applying irradiation field aperture, and processing the main reading image signal obtained by this main reading. A method for determining processing conditions, the method comprising: obtaining image data at each position on the recording medium from the main reading image signal obtained by the main reading, performing differential processing on this image data, and using the obtained differential value to perform the above processing. A method for determining image processing conditions, comprising: detecting an irradiation field on a recording medium, and determining the image processing conditions based on the main reading image signal within this irradiation field. (2) When the irradiation field is rectangular, the irradiation field is detected using the differential value by selecting the X and Y axes along two adjacent sides of the rectangular irradiation field contour, and A differential value is obtained, and the differential value is aggregated in the Y-axis direction to determine the position of the above contour on the X-axis.A differential value is also obtained in the Y-axis direction, and this differential value is aggregated in the 2. The image processing condition determining method according to claim 1, wherein the method is performed by determining the position of the contour on the Y-axis. (3) The detection of the irradiation field using the differential value is performed by first selecting an arbitrary position where the differential value is the maximum or a predetermined value or more as the first point of interest in the differential image composed of the differential value, and then selecting this point as the first point of interest. Find the position where the differential value is maximum among the surrounding positions adjacent to the first point of interest and set this as the second point of interest,
Next, search for the position with the maximum differential value among the surrounding positions adjacent to this second point of interest, excluding the previous point of interest, and define this as the third point of interest. The process of searching is repeated to find new points of interest one after another, and when a position adjacent to the first point of interest is found as a new point of interest, the inside of the closed curve connecting the previous points of interest is recognized as the irradiation field. 2. The image processing condition determining method according to claim 1, wherein the image processing condition determining method is performed by: (4) The detection of the irradiation field using the differential value is performed by first selecting an arbitrary position where the differential value is the maximum or a predetermined value or more as the first point of interest in the differential image composed of the differential value, and then selecting this point as the first point of interest. Search for a position whose differential value is greater than or equal to a predetermined value from among the surrounding positions adjacent to the first point of interest and set this as the second point of interest, and then Search for a position where the differential value is greater than or equal to a predetermined value from among the positions excluding the points of interest, define this as the third point of interest, and then repeat the process of searching for this third point of interest to find new points of interest one after another. A patent claim characterized in that, when a position adjacent to the first point of interest is found as a new point of interest, the inside of a closed curve connecting the previous points of interest is recognized as an irradiation field. The method for determining image processing conditions according to item 1. (5) When searching for a new point of interest after the second point of interest, if there are multiple points whose differential value is greater than or equal to a predetermined value among the adjacent surrounding positions, the adjacent surrounding positions must be Give a certain priority to
5. The image processing condition determining method according to claim 4, wherein the position having the highest priority among the plurality of positions whose differential value is equal to or greater than a predetermined value is set as the next new point of interest. (6) When searching for a new point of interest after the second point of interest, if there is no point among the adjacent surrounding positions whose differential value is greater than or equal to the predetermined value, then 5. The image processing condition determining method according to claim 4, wherein the position where the differential value is maximum is set as the next new point of interest. (7) The detection of the irradiation field performed using the differential value is a multivalued value having a portion corresponding to the irradiation field contour and each position in the portion corresponding to the irradiation field contour having a different value from each position in other portions. A large number of image templates are prepared in which the shape and size of the portion corresponding to the irradiation field contour differs depending on the shape and size of the irradiation field contour at various irradiation field apertures that can be used in actual imaging, and from the above differential value, Correlates the differential value on the differential image or the value obtained by processing this differential value with the value on each of the above templates, and recognizes that the area inside the portion corresponding to the irradiation field outline in the template with the highest correlation is the irradiation field. 2. The image processing condition determination method according to claim 1, wherein the image processing condition determining method is performed by: (8) The detection of the irradiation field using the differential value is performed by treating each position lined up in a predetermined direction as one line on the recording medium, differentially processing the image data on the line, and calculating the differential value. 2 where the absolute value of exceeds the predetermined value T_0
1 position on the line as an irradiation field contour candidate point, find the minimum value T_1 of the image data on the line between both irradiation field contour candidate points, and determine that the image data on the line has the minimum value T_1. Detecting two positions that are located on the outside of each line as irradiation field contour points on the line, and detecting the irradiation field contour points for each line in a predetermined range on the recording medium, Claim 1, characterized in that the method is carried out by recognizing the inside of the line connecting the irradiation field contour points in the irradiation field as the irradiation field.
Image processing condition determination method described in Section. (9) An x-axis and a y-axis that are orthogonal to each other are set on the recording medium, and the detection of the irradiation field contour point on the line is
9. The image processing condition determining method according to claim 8, wherein the method is performed for both the axial line and the y-axis line. (10) The detection of the irradiation field using the differential value is carried out by
A book line is defined as a book line, the image data on the line is differentiated, a position where the absolute value of the differential value exceeds a predetermined value T_0 is defined as an irradiation field contour candidate point on the line, and the position on the line at the candidate point is Obtain image data, obtain a characteristic value Th of the image data from the image data, detect a position on the line where the image data has the characteristic value Th as an irradiation contour point on the line, and determine the irradiation field contour. A patent characterized in that point detection is performed for each line in a predetermined range on the recording medium, and the area inside the line connecting the irradiation field contour points on each line is recognized as the irradiation field. An image processing condition determining method according to claim 1. (11) An x-axis and a y-axis that are orthogonal to each other are set on the recording medium, and detection of irradiation field contour points on the lines is performed for both the line in the x-axis direction and the line in the y-axis direction. An image processing condition determining method according to claim 10, characterized in that: (12) The detection of the irradiation field using the fine powder value is performed by detecting each position in a row in a predetermined direction on the recording medium.
A book line is assumed, and the image data on this line is subjected to differential processing, and a position where the absolute value of the differential value exceeds a predetermined value T_0 is detected as a visible irradiation field contour point on the line, and at the same time, at the visible irradiation field contour point, determining the image data, determining a characteristic value Th of the image data from the image data,
On the above line, the above image data is the above characteristic value Th
A position other than a position that is the same as or in the vicinity of the visible radiation field contour point is detected as a potential radiation field contour point among the positions, and the detection of the manifest and potential radiation field contour points is carried out at a predetermined position on the recording medium. Claim 1 is characterized in that the method is carried out for each line of the range, and the inside of the line connecting the actual and potential irradiation field contour points on each line is recognized as the irradiation field. Described method for determining image processing conditions.