JP4401140B2 - Diagnostic imaging support device - Google Patents

Description

  The present invention relates to an image diagnosis support apparatus, and more particularly to an image diagnosis support apparatus that displays a current image and a past image of the same examinee simultaneously on a display device such as a display.

  The conventional image diagnosis support apparatus reads the current image and the past image of the same examinee taken by the X-ray CT apparatus, and the body axis directions of both images so that the difference between the current image and the past image can be visually grasped. Are simultaneously displayed on an image display device such as a display.

As a method of aligning the positions of the current image and the past image, for example, a method of aligning the past image to a position considered to be equivalent to the current image by a user operation is generally used. In addition, as an alignment method without user operation, there is a method of acquiring a two-dimensional image having the highest correlation with a two-dimensional current image from a three-dimensional past image (Patent Document 1).
JP 2003-153082 A

  However, in the case of the alignment method described in Patent Document 1, there are many non-reproducible factors such as the breathing state, heart pulsation, and table position at that time, even for the same examinee. The image features do not always match, and there are variations in the search accuracy of past images having the highest correlation with the current image.

  If the positions of the current image and the past image are misaligned, an operation for correcting the misalignment must be performed by the operation of the doctor, which is a burden on the doctor. If there is an accurate alignment method that can also adjust the anatomical position without being influenced by such factors, the doctor's operation regarding interpretation can be omitted and the diagnostic ability of the doctor can be improved. I can expect.

  The present invention has been made in view of such circumstances, and can simultaneously display a current image and a past image at the same position of the same examinee, and in particular, a chest image taken on the day which is a tomographic image orthogonal to the body axis. An object of the present invention is to provide an image diagnosis support apparatus capable of accurately aligning a (current image) and a previously captured chest image (past image).

In order to achieve the above-mentioned object, the invention according to claim 1 is the same imaged chest image (current image) and past imaged chest image (past image) of the same examinee, which are a plurality of tomographic images obtained by the medical imaging device. In the image diagnosis support apparatus that simultaneously reads both images on the image display means, the extraction means for extracting the trachea and bronchus from the current image and the past image, and the bronchi that first branches from the trachea extracted by the extraction means A bronchial bifurcation part discriminating unit for discriminating the bifurcation part for each of the current image and the past image, and a body axis direction based on the current image and the past image corresponding to the bronchial bifurcation part respectively discriminated by the bronchial bifurcation part discriminating unit Image positioning means for displaying the current image and the past image at the same position on the image display means, That.

  That is, the trachea or bronchus is extracted from each image of the chest image (current image) taken on the day which is a plurality of tomographic images obtained by scanning in the body axis direction with a medical imaging apparatus such as an X-ray CT apparatus or an MRI apparatus. The current image corresponding to the bronchial bifurcation that first branches from one trachea is retrieved from the plurality of current images. Note that the current image corresponding to the bronchial bifurcation may be either an image immediately before the trachea is first branched or an image immediately after it.

  Similarly, a past image corresponding to a bronchial bifurcation is searched from a plurality of past images for past photographed chest images (past images) of the same examinee. Then, the current image and the past image corresponding to the bronchial bifurcation are regarded as images at the same position in the body axis direction, and the current image and the past image are aligned based on these images.

In the image diagnosis support device according to claim 1, wherein the extraction means performs a binarization process for the current image or a past image by a threshold value for extracting the air region, and extracted by binarization The trachea and bronchus are determined from the size, shape, and number of regions.

  Since the trachea or bronchus is an air region, the trachea or bronchus can be extracted by binarizing the current image or the past image with a threshold value for extracting the air region. Further, the trachea and bronchus are extracted with high accuracy from the size of the extracted region (the number of pixels corresponding to the size of a general trachea and bronchus), shape (circularity), and number.

Further, in the diagnostic imaging support apparatus according to claim 1, the bronchial bifurcation part discrimination means sequentially extracts a plurality of current images and past images from the head side toward the leg side by the extraction means. Extraction is performed, and a branch portion where the extracted trachea first branches is determined as a bronchial branch portion.

  That is, the trachea is sequentially extracted from the head side to the leg side for a plurality of current images. Since the chest image is targeted, one trachea is usually extracted from the image on the head side. When the trachea is sequentially extracted toward the leg side, a bronchial bifurcation that branches into two tracheas can be extracted. In this way, the bronchial bifurcation where one trachea first branches is searched.

  The image diagnosis support apparatus according to claim 1, wherein the image alignment unit includes a misalignment between the current image and the past image corresponding to the bronchial bifurcation determined by the bronchial bifurcation determining unit in the opposite axial direction. And the positions of the current image displayed on the image display means and the past image in the body axis direction are matched based on the positional deviation.

  For example, when the past image corresponding to the bronchial bifurcation is shifted 20 (mm) toward the leg with respect to the current image corresponding to the bronchial bifurcation, the current image at an arbitrary slice position Z (mm) in the body axis direction The past image corresponding to is that corresponding to the slice position of Z + 20 mm.

According to a second aspect of the present invention, in the diagnostic imaging support apparatus according to the first aspect, the image alignment unit includes a current image and a past image corresponding to the bronchial bifurcation determined by the bronchial bifurcation determining unit. The positional deviation in the direction of the opposite axis, and the positional deviation of the trachea or bronchus in each image between the current image and the past image, and the body axes of the current image and the past image displayed on the image display means based on each positional deviation It is characterized in that the position of the direction is matched and the position of both images in each display area of the image display means is matched.

  That is, the positions of the current image and the past image in the body axis direction are matched, and the positions of both images in each display area of the image display means are also matched (for example, the trachea of both images is matched to the center of each display area). Let

  According to the present invention having the above configuration, the current image and the past image of the same slice position of the same examinee can be displayed at the same time, and in particular, the current image and the past corresponding to the bronchial bifurcation where one trachea branches first. Since images are searched and the current image and past image are aligned in the body axis direction based on these images, it is good even if the features of the current image and past image do not match exactly due to shooting conditions etc. Can be aligned. Thereby, it is possible to omit the operation of aligning the image of the doctor regarding interpretation, and it is possible to improve the diagnostic ability of the doctor.

  A preferred embodiment of an image diagnosis support apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

  First, the hardware configuration of the diagnostic imaging support apparatus according to the present invention will be described with reference to FIG.

  As shown in the figure, the diagnostic imaging support apparatus 10 mainly includes an image processing apparatus 20, an image display apparatus 30 that displays a medical image subjected to image processing by the image processing apparatus 20, and an image display apparatus 30 such as a keyboard and a mouse. And an external input device 40 for operating buttons and the like on the software displayed on the screen.

  The image processing device 20 includes a central processing unit (CPU) 22 that performs processing according to a program for image diagnosis support processing according to the present invention, calculation for detecting abnormal shadow candidates, and the like, and temporary processing of images displayed on the image display device 30. Memory 24 as a work area during program execution, a plurality of tomographic images, an operating system (OS), and an image diagnosis support process according to the present invention Are composed of a magnetic disk 26 in which various software including the above program are stored, and an interface (I / F) 28 for inputting and outputting tomographic images.

  Next, processing contents of the diagnostic imaging support apparatus 10 according to the present invention will be described.

  FIG. 2 is a flowchart showing an outline of processing of the diagnostic imaging support apparatus 10 according to the present invention.

(Step 1)
A current image and a past image of the chest imaged by an X-ray CT apparatus (not shown) are read and stored in the magnetic disk 26 of the image processing apparatus 20. Note that the X-ray CT apparatus scans the examinee in the body axis direction (from the head toward the leg), and captures a plurality of tomographic images of the chest at a predetermined slice interval.

(Step 2)
Of the current image and the past image stored in the magnetic disk 26 of the image processing apparatus 20, images (slice data) are sequentially read from the head side to the memory 24, and the trachea and bronchus are extracted from the slice data. .

  Hereinafter, the contents of the trachea and bronchi extraction process will be described with reference to FIG. Note that the processing after step 2 is processing for both the current image and the past image.

(Step 2-1)
A threshold value that distinguishes the air region (CT value: about −1000) from other regions is set for the slice data, and the slice data is binarized based on the set threshold value. The trachea and bronchi are air regions.

(Step 2-2)
It is determined whether there is an air region by binarization processing. If there is an air area, or if there is an area that has not yet been processed in the next step, the process proceeds to the next step. When there is no air region, or when the next step is performed for all regions, the bronchi extraction processing is terminated.

(Step 2-3)
Image processing by the region expansion method (region growing method) is performed on the air region distinguished by the binarization processing. In this region expansion method, first, a certain point of a region of interest (in this case, an air region) is selected, and then a point connected to the region is searched from neighboring pixels, and the region is expanded by capturing the connected point. This is a method of extracting a region of interest.

(Step 2-4)
The upper limit pixel number and the lower limit pixel number of the trachea or bronchial region are set in advance, and if the pixel number obtained in step 2-3 is within the range of this pixel number, the process proceeds to the next step. If it is out of range, the process is repeated again from step 2-2.

(Step 2-5)
The circularity of the region extracted by the processing up to step 2-4 is calculated. The circularity is represented by the following formula (1).
[Equation 1]
C = S / 4πR ² (Formula 1)
C: Circularity, S: Area of the region, R: Perimeter of the region In order to increase the difference in the circularity C shown in the above formula (1), the reciprocal of the circularity C may be taken.

(Step 2-6)
If the circularity obtained in step 2-5 is larger than a preset threshold value, the region is set as a trachea or bronchus region, and the trachea or bronchus extraction process is terminated. If the reciprocal of the circularity is taken in step 2-5, the region is set as a trachea or bronchus region when the value is smaller than a preset threshold value, and the trachea or bronchus extraction process is terminated.

(Step 3)
Returning to FIG. 2, bronchial bifurcation determination processing is performed on each slice data based on the position of the trachea or bronchus region extracted in step 2.

  Hereinafter, the processing content of the bronchial bifurcation determination processing will be described with reference to FIG.

(Step 3-1)
Based on the position of the tracheal region of the previous slice, the trachea or bronchial region position of the current slice is determined. Specifically, as shown in FIGS. 5A and 5B, the tracheal region 51 of the previous slice 50 is projected in parallel to the current slice 52, and if there is an overlapping portion, the overlapping region 54 is replaced with the tracheal region of the current slice 52. 53.

(Step 3-2)
Image processing by the region growing method is performed on the overlapping region that overlaps the tracheal region of the previous slice, and the number of pixels in the expanded region is obtained.

(Step 3-3)
The upper limit pixel number and lower limit pixel number of the trachea or bronchial region are set in advance, and if the pixel number obtained in step 3-2 is within the range of this pixel number, the process proceeds to the next step. If it is out of the range, it is considered that there is no trachea or bronchial region, and the bronchial bifurcation determination processing is terminated.

(Step 3-4)
The number of areas extracted by the processing so far is counted.

(Step 3-5)
When the number of regions counted in step 3-4 is one as shown in FIG. 5A, it is determined that the trachea 60 has not yet branched, and the next slice starts from step 3-1. Repeat the process. On the other hand, if there are two as shown in FIGS. 6 (A) and 6 (B), it is assumed that the trachea is branched (bronchi 62), and the process proceeds to the next step.

(Step 3-6)
As shown in FIG. 6A, the slice position of the previous slice 64 of the current slice 66 where the trachea 60 branches is held in the memory 24. In addition, the coordinate center of gravity of the tracheal region 68 is obtained in the previous slice 64, and the coordinates of the obtained center of gravity are stored.

(Step 4)
Returning to FIG. 2, the slice position of the current image immediately before the first branch of the trachea obtained in step 3 (hereinafter referred to as “current image corresponding to the bronchial bifurcation”) and one trachea branch first. Based on the slice position of the past image (hereinafter referred to as “the past image corresponding to the bronchial bifurcation”) immediately before the image processing, the current image and the past image are aligned.

  Hereinafter, the processing content of the image alignment processing will be described with reference to FIG.

(Step 4-1)
As shown in FIG. 8, the difference between the slice position of the current image 70 corresponding to the bronchial bifurcation obtained in step 3-6 and the slice position of the past image 72 corresponding to the bronchial bifurcation (body axis direction (Z coordinate) (Direction) difference).

  Thereby, the amount of positional deviation between the current image and the past image in the body axis direction becomes clear. Further, as shown in FIG. 9, the difference between the center of gravity coordinates of the tracheal region 68 (see FIG. 6) of the current image and the past image obtained in step 3-6 (the difference between the left and right directions of the body (X coordinate direction), and the front-back direction) (Difference in (Y coordinate direction)). As a result, the amount of positional deviation between the current image and the past image in the front-rear and left-right directions becomes clear.

(Step 4-2)
Based on the difference in the body axis direction between the current image and the past image obtained in step 4-1, the slice position of the past image corresponding to the displayed current image is obtained. Specifically, the past image at the slice position obtained by adding the difference in the body axis direction between the current image obtained in step 4-1 and the past image to the slice position of the displayed current image is set as the corresponding image.

  For example, when the difference between the current image obtained in step 4-1 and the past image is 20 mm and the slice position of the current image currently displayed is 100 mm, the past image at the position of 120 mm becomes the corresponding image. .

  Also, based on the difference between the barycentric coordinates of the tracheal area of the current image and the past image obtained in step 4-1, the barycentric position of the tracheal area of the current image and the barycentric position of the tracheal area of the past image are matched. Specifically, as shown in FIG. 10, the coordinate difference (X1−X2, Y1−Y2) of each barycentric position is obtained, and the display position in the display area of the past image corresponding to the difference as shown in FIG. Move.

  In addition, as shown in FIG. 12, the first bronchial branch, the left bronchial second bifurcation, and the right lung bronchial second bifurcation are extracted from the current / past image according to the procedure in step 3, and the respective centroids are calculated. To do. Then, three points in a three-dimensional space may be obtained, and three-dimensional alignment may be performed from the position difference between the three points.

As a specific example of the three-dimensional alignment method, first, 3 in the XYZ coordinate system is used.
The coordinates of the center of gravity of each point
First bifurcation bronchi of the current image _{(X n1, Y n1, Z} n1)
Second left bronchial bifurcation of the current image ( _Xn2l , _Yn2l , _Zn2l )
Right lung bronchi second bifurcation (X _n2r, Y _n2r, Z _n2r ) of the current image
Bronchial first bifurcation (X _P1 , Y _P1 , Z _P1 )
Left lung bronchus second bifurcation (X _P2l, Y _P2l, Z _P2l )
Second branch of right lung bronchus (X _P2r, Y _P2r, Z _P2r )
And the average of the three-axis position difference is calculated by the following equation (2).
[Equation 2]
X _AVE = {(X _n1 −X _P1 ) + (X _n2l −X _P2l ) + (X _n2r −X _P2r )} / 3
Y _AVE = {(Y _n1 −Y _P1 ) + (Y _n2l −Y _P2l ) + (Y _n2r −Y _P2r )} / 3
Z _AVE = {(Z _n1 −Z _P1 ) + (Z _n2l −Z _P2l ) + (Z _n2r −Z _P2r )} / 3
... (2)
Next, as shown in FIG. 13, the display position of the past image is shifted in accordance with the position difference obtained by Expression (2).

  The three-dimensional alignment may be a combination with a position indicating other anatomical features such as a xiphoid process or a clavicle, in addition to the combination of the first and second bronchial branches.

  Thereafter, each time the slice position of the current image to be displayed is changed, the processing of this step is performed to obtain a corresponding past image.

(Step 5)
As shown in FIG. 14, the current image and the past image at the position corresponding to the current image obtained in step 4-1 are displayed side by side in the left and right image display areas on the display screen of the image display device 30.

  In this embodiment, the trachea of each slice is sequentially extracted from the head side, and the current image corresponding to the bronchial bifurcation that uses the slice immediately before the slice where one trachea first branches as a reference for alignment is used. Alternatively, the past image is used. However, the present invention is not limited to this, and a slice in which one trachea first branches may be a current image or a past image corresponding to a bronchial bifurcation that is a reference for alignment.

  Further, in this embodiment, the current image and the past image are aligned in the body axis direction, and the alignment of both images in the front-rear and left-right directions is also performed. You can just add them together.

The figure which shows the hardware constitutions of the image diagnosis assistance apparatus which concerns on this invention The flowchart which shows the outline | summary of a process of the image diagnosis assistance apparatus which concerns on this invention. Flowchart for explaining processing contents of trachea and bronchi extraction processing Flowchart for explaining the processing content of bronchial bifurcation determination processing Figure used to explain tracheal or bronchial area discrimination Figure used to explain bronchial bifurcation discrimination Flowchart used to describe the processing contents of image alignment processing Figure showing the difference between the slice position of the current image and the past image corresponding to the bronchial bifurcation Figure to find the center of gravity coordinates at the bronchial bifurcation of the current image and the past image Figure for obtaining the center-of-gravity coordinate difference between the current image and the past image at the bronchial bifurcation The figure which shows the aspect which matches the gravity center of the bronchus bifurcation part of a present image and a past image from the difference of a gravity center coordinate The figure which shows the barycentric point of the bronchi first branch part, the left lung second branch part, and the right lung second branch part Diagram showing the three-dimensional alignment of the current image and the past image The figure which shows the aspect which arranges the present image and the past image on the same screen, and displays them on the display device

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Image diagnosis assistance apparatus, 20 ... Image processing apparatus, 22 ... Central processing unit (CPU), 24 ... Memory, 26 ... Magnetic disk, 28 ... Interface (I / F), 30 ... Image display apparatus, 40 ... External input Device, 50, 64 ... previous slice, 51, 53, 68 ... tracheal area, 52, 66 ... current slice, 54 ... overlapping area, 60 ... trachea, 62 ... bronchi, 70 ... current image corresponding to bronchial bifurcation, 72 ... Past image corresponding to bronchial bifurcation

Claims (6)

Load current image obtained by photographing the chest of the same testee are a plurality of tomographic images obtained by medical imaging apparatus, and a past image of the chest of the same testee obtained by photographing in the past, the In the image diagnosis support apparatus for displaying both images on the image display means simultaneously,
Extracting means for extracting the trachea region and bronchus region from the current image and the past image,
Based on the tracheal region and bronchial region extracted by the extracting means, bronchial bifurcation part discriminating means for discriminating the bronchial bifurcation part of the tracheal region with respect to the current image and the past image, respectively,
An image position for causing the image display unit to display the current image and the past image at the same position in the body axis direction with reference to the current image and the past image corresponding to the bronchial bifurcation determined by the bronchial bifurcation determination unit. Matching means;
An image diagnosis support apparatus comprising: The image registration means, the positional deviation of the body axis direction of the current image and the past image corresponding to the bronchial branching unit having determined respectively by bronchial branching unit discriminating means, and the in each image between the current image and the past image The position of the tracheal region or bronchial region is determined, the current image displayed on the image display means is matched with the position in the body axis direction based on the position shift, and the display areas of the image display means The image diagnosis support apparatus according to claim 1, wherein the positions of the two images are matched. The image registration means, before Kiki pipe branch or Kibe center of gravity of the first branch portion bronchi were determined, respectively, by determining means, the center of gravity of the bronchi second branch portion is determined respectively by the previous crisis pipe branch or Kibe discriminating means And a three-dimensional positional deviation between the current image and the past image corresponding to three points on the three-dimensional space extracted from the positions indicating the anatomical features included in the current image and the past image, respectively. The image diagnosis support apparatus according to claim 1, wherein a three-dimensional position of a current image and a past image displayed on the image display unit is matched based on the positional deviation. The bronchial bifurcation part discriminating means is photographed at a current slice position in the body axis direction among a plurality of tomographic images constituting each of the current image and the past image for each of the current image and the past image. A portion that overlaps the tracheal region included in the current slice by parallel projecting the tracheal region included in the previous slice taken at the previous slice position located on the head side of the current slice position along the body axis direction. The image diagnosis support apparatus according to claim 1, wherein a bronchial bifurcation of the trachea is determined based on the number of overlapping regions consisting of: The bronchial bifurcation determination unit causes the extraction unit to sequentially extract a trachea from a head side to a leg side with respect to a plurality of current images and past images, and the extracted trachea is first branched. The image diagnosis support apparatus according to claim 1, wherein a branching portion to be determined is determined as a bronchial branching portion .   The extraction means performs binarization processing on the current image or past image with a threshold value for extracting an air region, and determines the trachea and bronchus from the size and shape of the region extracted by the binarization processing The image diagnosis support apparatus according to claim 1, wherein:

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