JP2020146381A - Image processing device, image processing system, and program - Google Patents

Abstract

To correctly draw a disease condition in a region of interest, without being affected by variation or individual difference of the physique of a subject, an imaging condition, etc. in a medical image.SOLUTION: A control unit 21 in a console 2 sets, as reference signal values, different signal values of two or more places outside a region of interest to use for diagnosis, within a subject region in a radiation image, and calculates a contrast conversion function to apply to the radiation image, on the basis of the set reference signal values. Then, using the calculated contrast conversion function, the radiation image is subjected to gradation conversion.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image processing apparatus, an image processing system and a program.

Conventionally, image processing such as gradation processing has been performed for the purpose of making a radiation image obtained by irradiating a subject with radiation easier to see.

For example, Patent Document 1 describes that gradation processing is performed with reference to the signal values of the heart and lung fields of the chest radiographic image.
Further, in Patent Document 2, the average value of the thoracic spine portion or the shoulder portion of the thoracic radiographic image is used as a reference signal value so that the reference signal value becomes a predetermined output signal value and the contrast becomes constant. It is described that gradation conversion is performed.

JP-A-55-088740 Japanese Unexamined Patent Publication No. 2000-079110

In the diagnosis using the chest radiographic image, the diagnosis of the medical condition is performed mainly by focusing on the lung field area and paying attention to the concentration.

However, in Patent Document 1, since gradation conversion is performed with reference to the signal value of the region of interest, there is a risk that the gradation processing conditions may change depending on the density of the region of interest.
Further, in Patent Document 2, in order to keep the contrast constant, if the body shape and imaging conditions of the subject (for example, the positioning and body position of the subject) are constant, the difference in density depending on the medical condition is correctly depicted. be able to. However, if the body shape of the subject or the imaging conditions change, the density of the area of interest will be affected, and there is a risk that the density according to the medical condition cannot be accurately visualized.
The same applies not only to chest radiographic images, but also to radiographic images of other parts and medical images taken by other modalities different from radiographic imaging devices such as MRI (Magnetic Resonance Imaging).

An object of the present invention is to make it possible to correctly depict a medical condition in a region of interest in a medical image without being affected by changes in the body shape of the subject, individual differences, imaging conditions, and the like.

In order to solve the above problems, the image processing apparatus according to claim 1 is
A calculation means that sets two or more different signal values in the subject area of the medical image and outside the area of interest as the reference signal value, and calculates the contrast conversion function applied to the medical image based on the set reference signal value. When,
A gradation processing means for performing gradation conversion on the medical image using the contrast conversion function, and
To be equipped.

The invention according to claim 2 is the invention according to claim 1.
The region of interest is a region used for diagnosis within the subject region in the medical image.

The invention according to claim 3 is the invention according to claim 1 or 2.
The medical image is a chest image and the region of interest is the lung field region.

The invention according to claim 4 is the invention according to any one of claims 1 to 3.
The calculation means sets two or more different signal values including the reference signal value on the low concentration side and the reference signal value on the high concentration side as the reference signal value.

The invention according to claim 5 is the invention according to claim 4.
The calculation means includes the reference signal value on the low concentration side and a predetermined output concentration value on the low concentration side corresponding to the reference signal value on the low concentration side, and the reference signal value on the high concentration side and the high concentration. An equation of a straight line determined by a predetermined output density value on the high density side corresponding to the reference signal value on the side is calculated as the contrast conversion function.

The invention according to claim 6 is the invention according to claim 4 or 5.
The reference signal value on the low concentration side is a signal value of the vertebral body.

The invention according to claim 7 is the invention according to any one of claims 4 to 6.
The reference signal value on the high concentration side is a signal value in the periphery of the clavicle.

The invention according to claim 8 is the invention according to any one of claims 1 to 7.
A determination means for determining whether or not the inclination of the contrast conversion function calculated by the calculation means is out of a predetermined range is provided.

The invention according to claim 9 is the invention according to claim 8.
An adjusting means for adjusting the inclination of the contrast conversion function calculated by the calculating means is provided.

The invention according to claim 10 is the invention according to claim 9.
When the determination means determines that the inclination of the contrast conversion function is outside the predetermined range, the adjusting means adjusts the inclination of the contrast conversion function so that it is within the predetermined range.

The invention according to claim 11 is the invention according to any one of claims 1 to 10.
A display means for displaying the medical image whose gradation has been converted by the gradation processing means is provided.

The invention according to claim 12 is the invention according to claim 11.
The inclination of the contrast conversion function used for the gradation conversion is readjusted according to a user operation, and is provided with a readjustment means applied to the medical image.

The image processing system of the invention according to claim 13 is
The image processing apparatus according to any one of claims 1 to 10.
A display device that displays the medical image whose gradation has been converted by the gradation processing means, and
To be equipped.

The program of the invention according to claim 14
Computer,
A calculation means for calculating the slope of the contrast conversion function of the medical image based on two or more signal values in the subject area of the medical image and outside the area of interest used for diagnosis.
A gradation processing means that performs gradation conversion on the medical image by using the contrast conversion function.
To function as.

According to the present invention, it is possible to correctly depict the pathological condition of the region of interest in a medical image without being affected by changes in the body shape of the subject, individual differences, imaging conditions, and the like.

It is a figure which shows the whole structure of the image processing system in embodiment of this invention. It is a block diagram which shows the functional structure of the console of FIG. It is a flowchart which shows the gradation processing executed by the control part of FIG. It is a figure for demonstrating the calculation method of a contrast conversion function. It is a figure for demonstrating the method of adjusting the inclination of a contrast conversion function. (A) is a diagram showing a chest image of a subject whose body thickness is thicker than the standard body type and a subject of the standard body type and a histogram thereof, and (b) is a contrast conversion of the prior art to the chest image shown in (a). The figure which shows the image which performed the gradation conversion by the function and the graph of the contrast conversion function, (c) is the image which performed the gradation conversion by the contrast conversion function of this embodiment on the chest image shown in (a), and contrast conversion. It is a figure which shows the graph of a function. (A) is a diagram showing a chest image of the same subject taken at different times and a histogram thereof, and (b) is a gradation conversion of the chest image shown in (a) by a contrast conversion function of the prior art. The figure which shows the graph of the image and the contrast conversion function, (c) is the figure which showed the image which performed the gradation conversion by the contrast conversion function of this embodiment on the chest image shown in (a), and the graph of the contrast conversion function. .. It is a figure which shows the region of interest and the reference point at the time of performing gradation processing on an abdominal image.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

[Configuration of image processing system 100]
First, the configuration of this embodiment will be described.
FIG. 1 is a diagram showing an overall configuration example of the image processing system 100 according to the present embodiment. As shown in FIG. 1, the image processing system 100 is configured by connecting the photographing device 1 and the console 2 so that data can be transmitted and received.

The photographing device 1 includes a radiation detector 11b, a photographing table 11 to which the radiation detector 11b can be loaded, and a radiation generator 12. The photographing table 11 can be loaded with the radiation detector 11b in the holder 11a.

The radiation detector 11b is composed of a semiconductor image sensor such as an FPD (Flat Panel Detector), and is provided so as to face the radiation generator 12 with the subject H interposed therebetween. The radiation detector 11b has, for example, a glass substrate or the like, and detects radiation (X-rays) irradiated from the radiation generator 12 at a predetermined position on the substrate and transmitted at least through the subject H according to its intensity. A plurality of detection elements (pixels) that convert the detected radiation into an electric signal and store it are arranged in a matrix. Each pixel is configured to include a switching unit such as a TFT (Thin Film Transistor). The radiation detector 11b controls the switching unit of each pixel based on the image reading condition input from the console 2, switches the reading of the electric signal stored in each pixel, and stores the electric signal in each pixel. Image data is acquired by reading the electric signal. Then, the radiation detector 11b outputs the acquired image data to the console 2.
The image data output from the radiation detector 11b consists of signal values representing the density of each pixel.

The radiation generator 12 is arranged at a position facing the radiation detector 11b with the subject H in between, and is loaded into the holder 11a via the patient who is the subject H based on the radiation irradiation conditions input from the console 2. The radiation detector 11b is irradiated with radiation to take an image. The radiation irradiation conditions input from the console 2 include, for example, a tube current value, a tube voltage value, a radiation irradiation time, a mAs value, and a SID (the shortest distance between the radiation detector 11b and the tube of the radiation generator 12). The presence or absence of a grid, the type of grid, etc.

The console 2 outputs radiation irradiation conditions and image reading conditions to the photographing device 1 to control the radiation photographing and the reading operation of the radiation image by the photographing device 1, and also performs image processing on the radiation image acquired by the photographing device 1. Functions as an image processing device.
As shown in FIG. 2, the console 2 includes a control unit 21, a storage unit 22, an operation unit 23, a display unit 24, and a communication unit 25, and each unit is connected by a bus 26.

The control unit 21 includes a CPU (Central Processing Unit) and a RAM (Random Access Memory).
) Etc. The CPU of the control unit 21 reads out the system program and various processing programs stored in the storage unit 22 in response to the operation of the operation unit 23, expands them in the RAM, and operates each unit of the console 2 according to the expanded program. In addition, the irradiation operation and the reading operation of the photographing device 1 are centrally controlled. In addition, various processes such as gradation processing, which will be described later, are executed on the radiation image transmitted from the radiation detector 11b of the photographing apparatus 1.
By executing the gradation processing shown in FIG. 3, the control unit 21 functions as a calculation means, a gradation processing means, a determination means, an adjustment means, and a readjustment means.

The storage unit 22 is composed of a non-volatile semiconductor memory, a hard disk, or the like. The storage unit 22 stores data such as parameters or processing results necessary for executing processing by various programs and programs executed by the control unit 21. Various programs are stored in the form of a readable program code, and the control unit 21 sequentially executes an operation according to the program code.

For example, the storage unit 22 stores the irradiation conditions and the image reading conditions corresponding to the imaging site. Further, the storage unit 22 stores shooting order information transmitted from a RIS (Radiology Information System) or the like (not shown). The imaging order information includes patient information, examination information (examination ID, imaging site (including imaging direction such as front, side surface, A → P, P → A), body position, examination date, etc.).

In addition, the storage unit 22 stores the radiographic image acquired by imaging and the image generated by image processing in association with patient information and examination information.

The operation unit 23 is configured to include a keyboard equipped with cursor keys, number input keys, various function keys, and a pointing device such as a mouse, and controls an instruction signal input by key operation on the keyboard or mouse operation. Output to 21. Further, the operation unit 23 may include a touch panel on the display screen of the display unit 24, and in this case, the operation unit 23 outputs an instruction signal input via the touch panel to the control unit 21. Further, the operation unit 23 is provided with an exposure switch for instructing the radiation generator 12 to perform dynamic imaging.

The display unit 24 is composed of a monitor such as an LCD (Liquid Crystal Display) or a CRT (Cathode Ray Tube), and displays input instructions, data, and the like from the operation unit 23 according to instructions of display signals input from the control unit 21. To do.

The communication unit 25 has an interface for transmitting and receiving data with the radiation generator 12 and the radiation detector 11b. The communication between the console 2, the radiation generator 12 and the radiation detector 11b may be wired communication or wireless communication.
Further, the communication unit 25 includes a LAN adapter, a modem, a TA (Terminal Adapter), etc., and controls data transmission / reception with a RIS or the like (not shown) connected to the communication network.

[Operation of image processing system 100]
When the radiation detector 11b is set in the holder 11a in the imaging device 1 and the imaging order information to be imaged is selected by the operation unit 23 on the console 2, the radiation irradiation conditions and the radiation irradiation conditions according to the selected imaging order information The radiation image reading condition is read from the storage unit 22 and transmitted to the photographing apparatus 1. When the subject H is positioned and the exposure switch is pressed, radiation is emitted by the radiation generator 12 in the photographing device 1, and the image data of the radiation image is read by the radiation detector 11b, and the read image is read. The data (referred to as radiation image G) is transmitted to the console 2.

When the communication unit 25 receives the radiation image G from the radiation detector 11b on the console 2, the control unit 21 executes gradation processing (density conversion processing). In this embodiment, a case where the radiographic image G is a chest radiographic image and the lung field region is used as a region of interest for diagnosis will be described as an example.

FIG. 3 is a flowchart showing the flow of gradation processing. The gradation processing is executed in cooperation with the program stored in the control unit 21 and the storage unit 22.

First, the control unit 21 recognizes the subject area from the received radiation image G (step S1).
In step S1, for example, a histogram of the signal value of the radiation image G is created, a threshold value for separating the subject area and the background area is determined from the histogram, and a region having a signal value lower than the determined threshold value is recognized as the subject area. The threshold value can be determined by using, for example, a discriminant analysis method, a p-tile method, a fixed threshold value method, a mode method, or the like. Alternatively, the threshold value may be determined by machine learning using a neural network, feature extraction, clustering, or the like.

Next, the control unit 21 sets two different signal values in the subject region of the radiation image G outside the region of interest as reference signal values for calculating the contrast conversion function (step S2).
The reference signal value is a signal value output at a predetermined output density value by gradation processing using a contrast conversion function.
In step S2, two signal values, a signal value on the high density side and a signal value on the low density side of the subject area, are determined as reference signal values. The signal value on the high density side is, for example, a signal value higher than the average of the signal values in the subject area, and the signal value on the low density side is, for example, a signal value lower than the average of the signal values in the subject area. Alternatively, the signal value on the high density side is a histogram of the signal value of the radiation image G or a signal value of the upper m% or more of the cumulative histogram, and the signal value on the low density side is a histogram or the cumulative histogram of the signal value of the radiation image G. It is a signal value of the lower n percent or less (m and n are positive numbers). Alternatively, the signal value on the high density side may be a signal value higher than the median of the signal values in the subject area, and the signal value on the low density side may be a signal value lower than the median of the signal values in the subject area.

For example, two locations with preset coordinates, coordinates on the area automatically extracted by the area recognition process, coordinates set as reference points in the past image, or coordinates selected from the image by user operation as reference points. The signal value of the reference point is set as the reference signal value. The area recognition process can be performed using, for example, an area division algorithm such as template matching or graph cutting, or machine learning such as neural network, feature extraction and clustering.
The two reference points are in the subject area and outside the area of interest, which are less affected by the body shape and shooting conditions of the subject than the area of interest, and the density does not change depending on the medical condition. It is preferable to provide it in the region on the high concentration side. For example, a point on the vertebral body can be used as the reference point on the low concentration side, and a point on the peripheral portion of the clavicle (the portion having a high concentration above or below the clavicle) can be used as the reference point on the high concentration side. By doing so, the vertebral body on the low concentration side and the clavicle peripheral part on the high concentration side, which do not change in concentration depending on the medical condition, are not affected by the body shape of the subject, the imaging conditions, etc. It is possible to accurately depict the concentration change due to the pathological condition of the region of interest.
The reference point on the high concentration side may be set around the clavicle of the right shoulder, around the clavicle of the left shoulder, or around the clavicle of both shoulders. Further, a representative value (for example, an average signal value, a maximum value, a minimum value, etc.) of a predetermined region including a reference point (for example, a vertebral body region or a clavicle peripheral region) may be used as a reference signal value.

Next, the control unit 21 calculates the formula of the contrast conversion function based on the set reference signal value (step S3).
For example, as shown in FIG. 4, the control unit 21 has a predetermined low density side output density value O1 corresponding to the set low density side reference signal value D1 and the low density side reference signal value D1. , And the equation of the straight line L determined by the predetermined output density value O2 corresponding to the set reference signal value D2 on the high density side and the reference signal value D2 on the high density side is calculated as a contrast conversion function. Find the slope.

Next, the control unit 21 determines whether or not the inclination of the contrast conversion function is out of the predetermined range (step S4).
When it is determined that the inclination of the contrast conversion function is out of the predetermined range (step S4 ;; YES), the control unit 21 adjusts the inclination of the contrast conversion function to be within the predetermined range (step S5). The process proceeds to step S6.
In step S5, for example, as shown in FIG. 5A, when the slope of the contrast conversion function (straight line L) is outside the range of the predetermined upper limit L1 and lower limit L2 of the slope, FIG. 5B As shown in, on the graph, the contrast conversion function (straight line L) corresponds to any one of the reference signal values (reference signal value D2 in FIG. 5 (b)) and the output density value (in FIG. 5 (b)). After passing through the intersection of O2), the slope is adjusted to be a predetermined upper limit L1 or lower limit L2. Alternatively, the reference signal value (position of the reference point) may be adjusted so that the slope of the contrast conversion function falls within a predetermined range according to the histogram of the signal value in the subject area.
The inclination of the contrast conversion function may be adjusted automatically by the control unit 21 or by a user operation. When adjusting by user operation, for example, as shown in FIGS. 5A and 5B, the current contrast conversion function (straight line L), the upper limit L1 and the lower limit L2 of the predetermined inclination range are displayed on the graph. It may be displayed on the screen and adjusted by the user operating the straight line L by the operation unit 23. Alternatively, the graph and the signal value histogram may be superimposed and displayed, and the user may adjust the reference signal value by the operation unit 23.
By adjusting the slope of the contrast conversion function so that it is within a predetermined range, it is possible to prevent the lung field concentration from becoming extremely bright or too dark.

When the slope of the contrast conversion function is within a predetermined range (step S4; NO), the control unit 21 shifts to step S6.
Even if the inclination of the contrast conversion function is within a predetermined range, the inclination of the contrast conversion function may be adjusted.

In step S6, the control unit 21 applies the calculated (adjusted) contrast conversion function to perform gradation conversion on the radiation image G (step S6), and displays the gradation-converted radiation image G on the display unit 24. (Step S7).

Next, the control unit 21 determines whether or not the contrast readjustment is instructed by the operation unit 23 (step S8).
When it is determined that the contrast readjustment is instructed (step S8; YES), the control unit 21 displays the contrast readjustment screen (not shown) on the display unit 24, and the radiation image is according to the operation of the operation unit 23 by the user. The inclination of the contrast conversion function of G is readjusted (step S9), and the readjusted contrast conversion function is applied to perform gradation conversion on the radiation image G and display it on the display unit 24 (step S10).

Next, the control unit 21 determines whether or not the operation unit 23 has instructed the end of the readjustment (step S11). If it is determined that the end of readjustment has not been instructed (step S11; NO), the control unit 21 returns to step S8.
When the contrast readjustment is not instructed in step S8 (step S8; NO), or when it is determined in step S11 that the end of readjustment is instructed (step S11; YES), the control unit 21 determines the gradation. End the process.

Hereinafter, when one reference point is provided outside the region of interest in the subject area, a gradation processing result (conventional technique; see FIGS. 6 (b) and 7 (b)) and two points are provided (the present embodiment). The gradation processing results of FIGS. 6 (c) and 7 (c) will be described.

The left side of FIG. 6A is a histogram of the radiation image (chest image) A1 of the chest of the subject A and its signal value, and the right side is a histogram of the chest image B1 of the subject B and its signal value. It is shown in. Subject A is a patient with a body thickness thicker than the standard body type, and subject B is a patient with a standard body type.

The left side of FIG. 6B passes through the intersection of the signal value D11 of the reference point P11 and the predetermined output concentration value O1 with respect to the chest image A1 with the point P11 on the vertebral body of the chest image A1 as the reference point. It is a graph which showed the image A11 obtained by performing gradation conversion using the straight line L11 of the inclination α as a contrast conversion function, and the graph of the straight line L11 superimposed on the histogram of the signal value of the chest image A1. On the right side, with respect to the chest image B1, a straight line L21 having a slope α passing through the intersection O1 of the signal value D21 of the reference point P21 and the predetermined output concentration value is drawn with the point P21 on the vertebral body of the chest image B1 as the reference point. It is a graph which showed the image B11 obtained by performing the gradation conversion as a contrast conversion function, and the graph of the straight line L21 superimposed on the histogram of the signal value of the chest image B1.

On the left side of FIG. 6C, with respect to the chest image A1, the point P11 on the vertebral body of the chest image A1 and the point P12 above the clavicle are used as reference points, and the signal value D11 of the reference point P11 and a predetermined low concentration are used. Obtained by performing gradation conversion using a contrast conversion function as a straight line L12 passing through the intersection of the output density value O1 on the side and the signal value D12 of the reference point P21 and the output density value O2 on the high density side. It is the graph which showed the graph of the straight line L12 superimposed on the histogram of the signal value of the image A12 and the chest image A1. On the right side, with respect to the chest image B1, the point P21 on the vertebral body of the chest image B1 and the point P22 on the upper part of the clavicle are used as reference points, and the signal value D21 of the reference point P21 and the output concentration value O1 on the low concentration side predetermined. Image B12 obtained by performing gradation conversion using the straight line L22 passing through the intersection of the signal value D22 of the reference point P22 and the signal value D22 of the reference point P22 and the output density value O2 on the high density side as a contrast conversion function, and the chest. It is a graph which showed the graph of the straight line L22 superimposed on the histogram of the signal value of image B1.

In the histograms shown in FIGS. 6 (a) to 6 (c), the region indicated by the dot band indicates the range of the signal value (concentration) of the lung field region.

Since the body thickness of the subject A is thicker than that of the subject B, the abdominal concentration between the concentration of the vertebral body and the concentration of the lung field is as shown by an arrow in the histogram of FIG. 6 (b). , It is larger than that of the standard body type subject B, and the distance from the concentration of the vertebral body to the concentration of the lung field is extended. Therefore, when a predetermined contrast conversion function of the slope α passing through the intersection of the reference signal value D11 and the output concentration value O1 with the point P11 on the vertebral body as the reference point is applied, it is shown by a alternate long and short dash line in FIG. 6 (b). As described above, the output density of the lung field is higher than it should be, and the lung field is visualized dark as shown in the chest image 11. Therefore, it cannot be recognized that there is a lesion in the lung field.

On the other hand, as shown in FIG. 6C, a reference point is provided not only on the vertebral body on the low concentration side but also on the upper part of the clavicle on the high concentration side, and is predetermined as the signal value D11 of the reference point P11 of the vertebral body. When the contrast conversion function is calculated and applied by a straight line passing through the intersection of the output density value O1 on the low concentration side and the signal value D12 of the reference point P12 on the upper part of the clavicle and the intersection of the output concentration value O2 on the high concentration side determined in advance, As in the chest image A12, the affected lung field is visualized in white and at an appropriate density, reflecting the lesion.

Further, the left side of FIG. 7A is a chest image C1 of the chest of the subject C having a standard body shape and a lesion in the lung field and a histogram of the signal values thereof, and the right side is different from the case where the chest image C1 was taken. A histogram of the chest image C2 of the subject C and its signal value taken at the same time (the chest image C2 is taken before the lesion occurs and the chest image C1 is taken after the lesion occurs) is schematically shown. The chest image C1 and the chest image C2 have the same subject, but the imaging conditions are different. Specifically, the positioning is different (only the chest image C1 reflects the right arm), and the presence or absence of a foreign substance is different (only the chest image C1 has a foreign substance such as metal embedded in the body).

The left side of FIG. 7B is the inclination of the chest image C1 through the intersection of the signal value of the reference point P31 and the predetermined output concentration value O1 with the point P31 on the vertebral body of the chest image C1 as the reference point. It is a graph which showed the image C11 obtained by performing gradation conversion using the straight line L31 of α as a contrast conversion function, and the graph of the straight line L31 superimposed on the histogram of the signal value of the chest image C1. On the right side, with respect to the chest image C2, a straight line L41 having a slope α passing through the intersection of the signal value D41 of the reference point P41 and the predetermined output concentration value O1 with the point P41 on the vertebral body of the chest image C2 as the reference point. It is a graph which superposed the graph of the straight line L41 on the histogram of the signal value of the image C21 obtained by performing the gradation conversion as a contrast conversion function, and the chest image C2.

On the left side of FIG. 7 (c), with respect to the chest image C1, the point P31 on the vertebral body of the chest image C1 and the point P32 above the clavicle are used as reference points, and the signal value D31 of the reference point P31 and a predetermined low concentration are used. Obtained by performing gradation conversion using a contrast conversion function as a straight line L32 passing through the intersection of the output density value O1 on the side and the signal value D32 of the reference point P32 and the output density value O2 on the high density side. It is the graph which showed the graph of the straight line L32 superimposed on the histogram of the signal value of the image C12 and the chest image C1. On the right side, with respect to the chest image C2, the point P41 on the vertebral body and the point P42 on the upper part of the clavicle of the chest image C2 are used as reference points, and the signal value D41 of the reference point P41 and the output concentration value O1 on the low concentration side predetermined. Image C22 obtained by performing gradation conversion using a straight line L42 passing through the intersection of the signal value D42 of the reference point P42 and the signal value D42 of the reference point P42 and the output density value O2 on the high density side predetermined as a contrast conversion function, and the chest. It is a graph which showed the graph of the straight line L42 superimposed on the histogram of the signal value of image C2.

In the histograms shown in FIGS. 7 (a) to 7 (c), the region indicated by the dot band indicates the range of the signal value (concentration) of the lung field region.

The chest image C1 of the subject C reflects a foreign substance reflected at a concentration between the concentration of the vertebral body such as the bone and metal of the arm and the concentration of the lung field, and is therefore shown by an arrow in FIG. 7 (b). In addition, the concentration range from the concentration of the vertebral body to the concentration of the lung field is wider than the chest image C2 without these reflections, and the distance between the signal value of the vertebral body on the input side on the graph and the signal value of the lung field becomes longer. .. Therefore, when the contrast conversion function defined by the intersection of the signal value D31 of the vertebral body and the predetermined output density value O1 and the predetermined slope α is applied, as shown by the alternate long and short dash line in FIG. 7B, the original The output density of the lung field is higher than that of the lung field, and the lung field is visualized darkly as shown in the chest image C11. Therefore, it cannot be recognized that there is a lesion in the lung field of the lung field.

On the other hand, as shown in FIG. 7 (c), a reference point is provided not only at the point P31 on the vertebral body on the low concentration side but also at the point P32 on the upper clavicle on the high concentration side, and the signal of the reference point of the vertebral body is provided. Contrast conversion function by a straight line L32 passing through the intersection of the value D31 and the predetermined low concentration side output concentration value O1 and the signal value D32 of the reference point on the upper clavicle and the predetermined high concentration side output concentration value O2. When calculated and applied, as shown in the chest image C12, even if a foreign substance such as an arm bone or metal reflected at a low concentration is reflected, the affected lung field has an appropriate concentration reflecting the lesion, that is, Delineated at a lower density than the lesion-free chest image C22.

As described above, the control unit 21 of the console 2 sets two or more different signal values in the subject area in the radiographic image and outside the area of interest used for diagnosis as the reference signal value, and sets the reference signal value. Based on, the contrast conversion function applied to the radiographic image is calculated. Then, the calculated contrast conversion function is used to perform gradation conversion on the radiation image.
Therefore, it is possible to correctly depict the medical condition of the region of interest without being affected by changes in the body shape of the subject, individual differences, imaging conditions, and the like.

The description content in the above embodiment is a preferable example of the present invention, and is not limited thereto.

For example, in the above embodiment, the case where the console 2 that controls the photographing device 1 has a function as an image processing device has been described, but the image processing device may be a separate body from the console. Further, the display device for displaying the gradation processing result may be integrated with the image processing device or may be a separate body.

Further, in the above embodiment, the case where the present invention is applied when performing gradation conversion on the radiation image of the chest has been described as an example, but the present invention can also be applied to the radiation image obtained by photographing other parts. Is. For example, the processing target of the gradation processing described in FIG. 3 is a radiographic image of the abdomen, and as shown in FIG. 8, the reference point on the low density side is the point P5 on the bone region such as the spine, and the reference point on the high density side. Is set to the point P6 on the skin line, and the contrast conversion function is calculated by the method described in FIG. 3 to perform gradation conversion, thereby affecting the changes in the body shape of the subject, individual differences, shooting conditions, and the like. It is possible to correctly depict the pathological condition of the abdominal region as the region of interest without receiving it. Here, the abdominal region refers to a region of soft tissue from the lower end of the lung field to the upper end of the ilium, which does not include the spine, as shown by being surrounded by a dotted line in FIG.

Further, in the above embodiment, the reference signal value for calculating the contrast conversion function is set to the reference signal value at two places, but it may be set to two or more places.

Further, in the above embodiment, the case where the present invention is applied to a radiographic image has been described, but the present invention relates to a medical image taken by another modality different from that of a radiological imaging apparatus such as MRI. Is also applicable.

Further, for example, in the above description, an example in which a hard disk, a non-volatile memory of a semiconductor, or the like is used as a computer-readable medium for the program according to the present invention has been disclosed, but the present invention is not limited to this example. As another computer-readable medium, a portable recording medium such as a CD-ROM can be applied. A carrier wave is also applied as a medium for providing data of the program according to the present invention via a communication line.

In addition, the detailed configuration and detailed operation of each device constituting the image processing system can be appropriately changed without departing from the gist of the present invention.

100 Image processing system 1 Imaging device 11 Imaging device 11 Imaging table 11a Holder 11b Radiation detector 12 Radiation generator 2 Console 21 Control unit 22 Storage unit 23 Operation unit 24 Display unit 25 Communication unit 26 Bus

Claims (14)

A calculation means that sets two or more different signal values in the subject area of the medical image and outside the area of interest as the reference signal value, and calculates the contrast conversion function applied to the medical image based on the set reference signal value. When,
A gradation processing means for performing gradation conversion on the medical image using the contrast conversion function, and
An image processing device comprising. The image processing apparatus according to claim 1, wherein the region of interest is a region used for diagnosis in the subject region in the medical image. The image processing apparatus according to claim 1 or 2, wherein the medical image is a chest image, and the region of interest is a lung field region. The calculation means according to any one of claims 1 to 3, wherein two or more different signal values including a reference signal value on the low concentration side and a reference signal value on the high concentration side are set as the reference signal value. Image processing device. The calculation means includes the reference signal value on the low concentration side and a predetermined output concentration value on the low concentration side corresponding to the reference signal value on the low concentration side, and the reference signal value on the high concentration side and the high concentration. The image processing apparatus according to claim 4, wherein the equation of a straight line determined by a predetermined output density value on the high density side corresponding to the reference signal value on the side is calculated as the contrast conversion function. The image processing apparatus according to claim 4 or 5, wherein the reference signal value on the low density side is a signal value of the vertebral body. The image processing apparatus according to any one of claims 4 to 6, wherein the reference signal value on the high concentration side is a signal value in the peripheral portion of the clavicle. The image processing apparatus according to any one of claims 1 to 7, further comprising a determination means for determining whether or not the inclination of the contrast conversion function calculated by the calculation means is out of a predetermined range. The image processing apparatus according to claim 8, further comprising an adjusting means for adjusting the inclination of the contrast conversion function calculated by the calculating means. When the determination means determines that the inclination of the contrast conversion function is outside the predetermined range, the adjusting means adjusts the inclination of the contrast conversion function so that it is within the predetermined range. Item 9. The image processing apparatus according to item 9. The image processing apparatus according to any one of claims 1 to 10, further comprising a display means for displaying the medical image whose gradation has been converted by the gradation processing means. The image processing apparatus according to claim 11, further comprising readjustment means for readjusting according to a user operation of the inclination of the contrast conversion function used for the gradation conversion and applying it to the medical image. The image processing apparatus according to any one of claims 1 to 10.
A display device that displays the medical image whose gradation has been converted by the gradation processing means, and
An image processing system equipped with. Computer,
A calculation means for calculating the slope of the contrast conversion function of the medical image based on two or more signal values in the subject area of the medical image and outside the area of interest used for diagnosis.
A gradation processing means that performs gradation conversion on the medical image by using the contrast conversion function.
A program to function as.

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