JP5121399B2 - Image display device - Google Patents

Description

  The present invention relates to an image display device for comparative interpretation of medical images.

  Currently, chest CT examinations for lung cancer and other chest diseases are being performed. If the disease is not confirmed by a single CT examination, the CT examination is performed again after a certain period (3 to 6 months), and a diagnosis is made based on the change of the disease candidate part of the medical image taken after a certain period. May do. In addition, even if it is judged by CT examination that the disease candidate site has a small suspicion of malignancy, to confirm whether the suspicion of malignancy tends to increase, or after treatment of the disease site, early signs of recurrence Periodic CT examination may be continued to detect. When performing such a CT examination, comparative interpretation of the past image and the latest image is essential.

  Some conventional image display software has a function of reading a plurality of volume data sets and displaying a plurality of images derived from the plurality of volume data sets on a screen. It is useful to display and compare the latest image and the past image at the same time using such software.

  However, there are many cases in which imaging cannot be performed with the body axis direction at the same time being completely taken due to deformation of the chest (lung) shape caused by breathing or deformation of the spine accompanying aging. Therefore, even if the latest image and the past image related to the axial cross section are displayed, the cross sections of the two images are not always the same anatomically.

  As a technique for solving the above problems, a method of displaying the same cross section using a registration technique (application number: P2006-195354, application number: P2007-163938) has been proposed. This is a method for obtaining the parallel movement amount and deformation amount of two image sets. Non-patent document 1 and non-patent document 2 can be cited as similar registration techniques.

If these techniques are used, it is considered that the same cross section can be displayed by performing image deformation using the obtained image deformation amount. In fact, it was confirmed that using the software prototyped by the inventors, the same cross section can be automatically displayed with high accuracy, and the problem of deformation due to respiration is improved.
“Intensity-based image registration using robust correlation coefficients” IEEE Trans Med Imaging, November 2004, Vol. 23, No. 11, pages 1430-44 IEICE Transactions, 2002, J85-D-II, No. 10, pp. 1613-1623

  It has become clear that the following problems appear in the comparative interpretation support software for simultaneous display of multiple images as described above.

  (1) For example, when the user changes the cross-sectional position of the latest image, the same anatomical cross-section (generally curved surface) of the past image corresponding to the changed position is generated, and the generated past image is updated on the screen. The “follow-up function” is useful. However, since the size of the reconstruction area in the slice direction in the two volume data sets is usually different, the calculated cross-section (curved surface) of the past image is limited even if the specified range of the cross-section position is limited in the latest image being operated. ) May be outside the reconstruction area and not displayed on the screen. In this case, the screen becomes black or white, and it is not clear in which direction the image should be sliced to return the screen to the reconstruction area from this state. For this reason, the user is greatly anxious, and as a result, the operability of the software is greatly impaired.

  (2) When the deformation of the chest or the like is significant, the calculation accuracy of the registration technique is not good, so the “cross-section tracking function” cannot be realized with the accuracy desired by the user, and a slightly different cross-section is calculated as the same cross-section. There is. In order to avoid this, it is necessary to manually correct or deform the calculated cross section, but the cross section is determined by many parameters, and design a simple operation method to realize this. Is difficult. Since the automatic alignment method does not work, it is conceivable to perform manual alignment of past images. However, in the first place, the problem that image deformation is necessary to display the same section again occurs.

  An object of the present invention is to provide an image display device that realizes improvement in interpretation accuracy in an image display device for comparative interpretation that displays a plurality of images simultaneously.

  An image display device according to an aspect of the present invention includes a storage unit that stores first volume data including a first reconstruction area and second volume data including a second reconstruction area, which have different scan times, and A cross-section designating unit for designating the position of the first display cross section relating to the first volume data, and a first cross-section image generation for generating data of the first cross-section image relating to the first display cross section at the designated position from the first volume data A second cross-sectional image generating unit for generating data of a second cross-sectional image related to a second display cross-section having an anatomically substantially the same position as the position of the first display cross-section from the second volume data; Based on the display unit that displays the generated first cross-sectional image and second cross-sectional image, the range of the first reconstruction area, and the range of the second reconstruction area, the position of the first display cross-section Includes a range limiting section that limits a constant extent possible, the.

  An image display device according to another aspect of the present invention includes a storage unit that stores first volume data including a first reconstruction area and second volume data including a second reconstruction area, which have different scan times. The first slice image data relating to the first display slice of the first volume data is generated from the first volume data, and the position of the first display slice is anatomically identical. A conversion formula calculation unit that calculates a first coordinate conversion formula for calculating a second display cross section of the second volume data, and applying the calculated first coordinate conversion formula to the first display cross section. A second display cross section calculating section for calculating the second display cross section; a second cross section position changing section for changing the position of the second display cross section while maintaining the calculated shape of the second display cross section; After changes are made Data of a second cross-sectional image relating to a second display cross-section, a second cross-sectional image generator generated from the second volume data, a display unit for displaying the generated first cross-sectional image and second cross-sectional image, It comprises.

  ADVANTAGE OF THE INVENTION According to this invention, in the image display apparatus for the comparative interpretation which displays a several image simultaneously, it becomes possible to implement | achieve the improvement of an interpretation accuracy.

  Embodiments of the present invention will be described below with reference to the drawings. The image display apparatus according to the present embodiment is an image display apparatus for comparative interpretation that displays two cross-sectional images relating to the same scan region of the same subject in parallel on the screen.

  FIG. 1 is a diagram illustrating a configuration of an image display device 1 according to the present embodiment. As shown in FIG. 1, the image display apparatus 1 includes a storage unit 12, a coordinate conversion formula calculation unit 14, a reference image generation unit 16, a comparative image generation unit 18, a display unit 20, an operation unit 22, a movement range restriction unit 24, And a control unit 26.

  The storage unit 12 stores reference volume data and comparison volume data with different scan times collected by an X-ray computed tomography apparatus or the like. The reference volume data and the comparison volume data are volume data based on the result of scanning the same scan site of the same subject. Typically, the reference volume data is the latest volume data, and the comparison volume data is past volume data. Further, it is assumed that the scan site is the chest.

  FIG. 2 is a diagram showing the structure of volume data. As shown in FIG. 2, the volume data has a quadrangular prism or cube shape. The slice direction of the volume data is defined on the Z axis. The volume data includes a reconstruction area RR and an empty area ER. The reconstruction area RR has a cylindrical shape, and is an area having pixel values such as CT values by reconstruction processing. The central axis of the reconstruction area RR is parallel to the Z axis. The reconstruction area RR includes actual data such as the biological area of the subject. The central axis of the reconstruction area RR and the major axis of the subject are substantially parallel. The empty area ER is an area of empty data having a prescribed pixel value. The reconstruction area in the reference volume data is referred to as a reference reconstruction area, and the reconstruction area in the comparison volume data is referred to as a comparison reconstruction area.

  The coordinate conversion formula calculation unit 14 calculates a coordinate conversion formula for calculating a coordinate point in the comparison volume data that is anatomically identical to the coordinate point in the reference volume data. Details will be described later.

  Based on the reference volume data, the reference image generation unit 16 generates cross-sectional image data related to a cross section designated by the operation unit 22 or the like described later. Hereinafter, a cross section related to the reference volume data is referred to as a reference cross section, and a cross section image related to the reference volume data is referred to as a reference image. Note that the shape of the “cross section” includes not only a plane but also a curved surface. Typically, the reference cross section is a plane perpendicular to the central axis of the reference reconstruction area.

  The comparative image generation unit 18 generates cross-sectional image data relating to a cross section at a position anatomically identical to the position of the reference cross section based on the comparison volume data. Hereinafter, the cross section related to the comparative volume data is referred to as a comparative cross section, and the cross sectional image related to the comparative volume data is referred to as a comparative image. Specifically, the comparison image generation unit 18 applies a coordinate conversion formula to each pixel of the reference section, and calculates the coordinates of each pixel of the comparison section that is anatomically identical to the coordinates of each pixel of the reference section. To do. When the comparative cross section is calculated, the comparative image generating unit 18 generates comparative image data relating to the comparative cross section. That is, the comparative image follows the reference image. The shape of the comparison cross section is a curved surface by a coordinate conversion formula. The comparative image generator 18 can also generate comparative image data at different positions while maintaining the shape of the comparative section. Further, the comparison image generation unit 18 can also calculate a comparison section having a planar shape perpendicular to the Z axis and including the anatomically identical point as the attention point on the reference section by applying a coordinate conversion formula. It is.

  The display unit 20 displays the reference image KI and the comparative image HI in parallel in a layout for comparative interpretation as shown in FIG. Further, the display unit 20 displays a slider (hereinafter referred to as a reference slider) KS indicating a position in the reference reconstruction area in the reference slider display area KSR. Further, the display unit 20 displays a slider HS (hereinafter referred to as a comparison slider) indicating a position in the comparison reconstruction area in the comparison slider display area HSR. The moving range of the slider coincides with the range along the Z axis of the reconstruction area. Hereinafter, a range along the Z-axis of the reconstruction area is simply referred to as a reconstruction area range. When the position of the reference slider is changed by an operation unit 22 described later, the position of the comparison slider is automatically changed in conjunction with the reference slider.

  The operation unit 22 is an input device for specifying a cross-sectional position and switching various modes. Typically, the operation unit 22 includes a mouse having a button and a rotation wheel. For example, when the user (doctor or the like) designates the position of the reference cross section by moving the reference slider on the image, the operation unit 22 controls the reference destination of the movement destination with respect to the reference image generation unit 16 and the comparison image generation unit 18. Enter the position of the reference section corresponding to the position of the slider. The reference cross-section position can also be specified by a mouse drag operation or wheel operation by the user. For example, the reference slider is moved according to the movement amount of the drag operation or the rotation amount of the rotary wheel, and the position of the corresponding reference cross section is designated. It is also possible to directly specify the position of the comparison section by operating the mouse.

  The movement range limiting unit 24 includes a range including both the range of the reference reconstruction area and the range of the comparison reconstruction area, that is, a range common to the range of the reference reconstruction area and the range of the comparison reconstruction area (hereinafter, The range in which the position of the reference display section can be specified (hereinafter referred to as a limited range) is limited to the product area. The movement range restriction unit 24 may set the restriction range to a range including at least one of the range of the reference reconstruction area and the range of the comparison reconstruction area (hereinafter referred to as a sum area) instead of the product area. . The movement range restriction unit 24 restricts the movement range of each slider to the restriction range.

  The control unit 26 controls each component as the center of the image display device 1.

  FIG. 4 is a diagram showing an outline of a processing procedure for comparative interpretation by the control unit 26. As shown in FIG. 4, the process for comparative interpretation is performed in the order of a registration process S1, a limit range determination process S2, and a range limit display process S3.

  By the registration process S1, a coordinate conversion formula from the reference volume data to the comparison volume data is calculated. By the limited range determination process S2, the range in which the cross section can be specified is determined when comparative interpretation of the reference image and the comparative image is performed. By the range restriction display process S3, the movement of the cross section of the reference image is restricted within the determined restriction range, and the comparison image is made to follow the reference image and displayed based on the coordinate conversion formula. Details of each process will be described below.

(Registration process)
In the registration process S1, the control unit 26 causes the coordinate conversion formula calculation unit 14 to perform the registration process. In the registration process S1, the coordinate conversion formula calculation unit 14 first extracts pulmonary blood vessel regions from the reference volume data and the comparison volume data, respectively. When the pulmonary vascular region is extracted, a plurality of pulmonary vascular bifurcation points are detected from each pulmonary vascular region by applying a region expansion method. Based on the similarity between the plurality of distances between the plurality of pulmonary blood vessel branch points derived from the reference volume data and the plurality of distances between the plurality of pulmonary blood vessel branch points derived from the comparison volume data, Correspondence between the derived pulmonary vascular branch point and the pulmonary vascular branch point derived from the comparison volume data is performed. The two corresponding pulmonary blood vessel branch points can be said to be anatomically identical. By performing this association process, the coordinate conversion formula calculation unit 14 calculates a coordinate conversion formula.

(Limit range determination process)
When the coordinate conversion formula is calculated, the control unit 26 causes the movement range restriction unit 24 to perform a restriction range determination process.

  FIG. 5 is a diagram showing the flow of the restriction range determination process by the movement range restriction unit 24. First, a plurality of evaluation points (hereinafter referred to as reference evaluation points) are set on the upper end surface and the lower end surface of the reference reconstruction area, respectively. Next, a plurality of evaluation points (hereinafter referred to as comparative evaluation points) are set in the comparison volume data by applying a coordinate conversion formula to each set reference evaluation point.

  FIG. 6 is a diagram illustrating the reference evaluation points and the comparative evaluation points set in Step SA1 and Step SA2. As shown in FIG. 6, the reference evaluation point KP is set in the vicinity of the edges of the upper end surface and the lower end surface of the reference reconstruction area KRR. For example, the number of reference evaluation points KP to be set is set to 8 points on the upper end surface and the lower end surface, respectively, for a total of 16 points. The greater the number of reference evaluation points KP, the more accurate the limit range determination process. A coordinate transformation formula is applied to each reference evaluation point KP, and each reference evaluation point KP is mapped to the comparative reconstruction area HRR. Depending on the setting location of the reference evaluation point, there is a case where the reference evaluation point protrudes from the comparative reconstruction area like the comparative evaluation point HP7 as a result of mapping. In this case, the comparative evaluation point HP7 that protrudes and the reference evaluation point KP7 corresponding to the comparative evaluation point HP7 are excluded from the subsequent processing, or moved to a nearby comparative reconstruction area. The shape of the comparison reconstruction area HRR shown in FIG. 6 is a shape when the coordinate conversion formula is applied to the entire comparison volume data. The cross section perpendicular to the Z-axis of the reference image capturing area KRR is circular, but the cross section of the comparative image capturing area HRR is not circular but distorted because it is generated by coordinate transformation.

  When the comparative evaluation points are set, the distance between each reference evaluation point and the initial reference cross section and the distance between each comparative evaluation point and the initial comparison cross section are calculated (step SA3).

  FIG. 7 is a diagram illustrating the distance between the initial cross section and the evaluation point calculated in step SA3. As shown in FIG. 7, an initial reference cross section is set in the reference volume data. The initial reference cross section is automatically set or set by the operation unit 22. The initial reference cross section is an XY plane perpendicular to the Z axis. For each reference evaluation point KP1 to KP16, the distance from the initial reference cross section is calculated. The distance is calculated by distinguishing the plus direction / minus direction along the Z axis from the initial reference cross section. The distance between the comparative evaluation point and the initial comparison cross section is calculated in the same manner. At this time, the initial comparison cross section is calculated by applying a coordinate conversion formula to the initial reference cross section. In FIG. 7, the initial reference cross section is the XY plane. However, the initial reference cross section may be inclined with respect to the Z axis, and may be an arbitrary cross section.

  The movement range restriction unit 24 determines the range of the reference reconstruction area based on the calculated reference evaluation points and the distance between the reference cross sections, and determines the range of the comparison reconstruction area based on each comparative evaluation point and the distance between the comparison cross sections. (Step SA4). Specifically, the maximum distance and the minimum distance are specified for the reference volume data and the comparison volume data from the plurality of distances calculated in step SA3. The range between the maximum distance and the minimum distance is the range of the reference reconstruction area or the comparison reconstruction area.

  The movement range restriction unit 24 determines a restriction range based on the determined range of the reference reconstruction area and the range of the comparison reconstruction area (step SA5). FIG. 8 is a diagram showing a cross-section movable range determined in step SA5. It is. The shape of the comparative reconstruction area HRR shown in FIG. 8 is the shape when the coordinate conversion formula is applied to the entire comparison volume data. When the product area is set as the limit range, a range included in both the range of the reference reconstruction area and the range of the comparative reconstruction area is determined. When the sum area is set as the limited range, a range included in at least one of the range of the reference reconstruction area and the range of the comparison reconstruction area is determined.

  In the case of the sum area, a reconstruction area is always displayed on at least one of the reference image and the comparison image. When the deformation is large, an area that cannot be displayed in the product area method due to the restriction of cross-sectional movement may occur near the end of the volume data. On the other hand, with the method of the sum area, even if the deformation is large, all areas can be displayed. However, in the sum area method, a reconstruction area may not be included in one image. In such a case, instead of displaying a black image at the designated cross-sectional position, it is preferable to display an image on the end face of the limited range close to the designated cross-section in light black. Further, instead of displaying in light black, a mark or a character indicating the direction in which the cross section should be moved (direction within the limit range) may be displayed in a superimposed manner. This mark indicates a direction such as an arrow or a triangle. The characters are “upper”, “lower”, and the like.

  As a method for further improving the accuracy of the limit range determination process, there are the following methods. The first product area is determined by the above limit range determination process, and further, evaluation points are set at the upper end and the lower end of the comparison volume data, and the reference volume data and the comparison volume data are set by the limit range determination process. And the second product area is determined. Then, the determined product area of the first product area and the second product area is set as the restriction range.

  In the restriction range determination process, the evaluation point is set in the reconstruction area. In this case, the limited range is limited to the reconstruction area, and a cross-sectional image related to the reconstruction area is always displayed. The setting place of the evaluation point is not limited to the above setting place. One example of the setting location is volume data, and another example is a living body region. When evaluation points are set in the living body area, the limited range is limited to the living body area of the subject.

  FIG. 9 is a diagram illustrating a flow of processing for setting an evaluation point in a living body region by the movement range restriction unit 24. First, the movement range restriction unit 24 performs threshold processing on the reference volume data to extract a living body region (step SB1). The CT value of the air region outside the living body region is -1000H. U. The CT value of the living body region is 0H. U. Degree. Therefore, if the threshold value is set to about −900, it is possible to extract a living body region.

  The movement range restriction unit 24 performs erosion processing on the extracted living body region, and thins the living body region, for example, by about 5 voxels (step SB2). Then, the movement range restriction unit 24 extracts a surface area from the eroded biological area (step SB3). Step SB3 may be deleted. By performing step SB3, the number of evaluation points to be set can be reduced, and the processing time of the limit range determination process can be shortened. When the surface area is extracted, the movement range restriction unit 24 picks up the coordinate points of the surface area (or the living body area) at random, and uses the picked-up coordinate points as reference evaluation points (step SB4). The number of coordinate points to be picked up is, for example, about 1/10 of the whole. Also, coordinate points may be picked up at regular intervals, for example, 10 in the X direction, 10 in the Y direction, and every 3 voxels in the Z direction.

  The above example is a method of determining the limit range when the cross section is translated in the Z-axis direction, but the evaluation points are similarly applied to movement (pan), rotation, and enlargement / reduction in other directions. Can be used to determine the limit range.

(Range restriction display processing)
When the limit range is determined, the control unit 26 starts a range limit display process. In the range restriction display process, the control unit 26 generates reference image data related to the initial reference cross section in the reference image generation unit 16 and comparative image data related to the initial comparison cross section in the comparison image generation unit 18. Then, the control unit 26 displays the reference image and the comparative image in a layout for comparative interpretation as shown in FIG. When a cross section is designated by the user via the operation unit 20, the control unit 26 controls the reference image generating unit 16 and the comparative image generating unit 18 so that data of the reference image and the comparative image corresponding to the designated cross section is obtained. And an image generated on the display unit 20 is generated. For this purpose, the comparative image is displayed following the reference image. At the time of following the cross section, the control unit 26 controls the movement range limiting unit 24 to limit the range in which the cross section can be designated by the operation unit 22 to the limit range determined by the limit range determination process.

  The restriction method of the specifiable range is a method of limiting the specifiable range of the cross section to a predetermined limit range. However, the present invention is not limited to this. For example, there is also a moveability determination process for determining whether or not the cross section can be moved to a designated cross section every time a cross section is designated. Hereinafter, a specific method of the movement availability determination process by the movement range restriction unit 24 will be described.

  FIG. 10 is a diagram showing the flow of the movement availability determination process. The movement range restriction unit 24 waits for the designation of the cross-sectional position (step SC1). In response to the user's designation of the cross-sectional position via the operation unit 20, the cross-sectional area restriction unit 24 starts the movement feasibility determination process. First, the cross-section range restriction unit 24 calculates the distance between the designated cross-section and each evaluation point (step SC2). When each distance is calculated, the cross-section range limiting unit 24 determines whether or not the section can be moved to the designated section based on the determination result of whether or not the reconstruction area is included in the designated section (Step SC3). ).

  FIG. 11 is a diagram for specifically explaining the process of step SC3, and shows the distance between the designated section AP and the evaluation point P. FIG. Each time a cross section is designated, the movement range restriction unit 24 calculates the distance between the designated cross section AP and each evaluation point. As shown in FIG. 11A, when the position of the cross-section AP1 is designated below the Z axis, if any one of the calculated distances includes a minus, the movement range restriction unit 24 moves to the designated position. It is determined that movement is possible. As shown in FIG. 11B, when no minus is included in the calculated plurality of distances, the movement range restriction unit 24 determines that the movement to the position of the designated cross section AP2 is impossible. In this way, by determining whether or not only the plus or minus is included in the distance between the designated cross section and the evaluation points set on the upper end surface and the lower end surface of the reconstruction area RR, the designated cross section is determined. It is determined whether or not a reconstruction area is included in. Then, based on this determination result, it is determined whether or not it is possible to move to the designated cross section.

  If it is determined in step SC3 that the movement is possible, the movement range restriction unit 24 moves the surface position to the designated cross section (step S4). When the cross section is moved, the moveability determination process is terminated.

  If it is determined in step SC4 that the movement is impossible, the movement range restriction unit 24 determines whether the distance between the cross section before the designation and the cross section after the designation is one movement unit (for example, one movement unit = 1 voxel). Determination is made (step SC5).

  When it is determined in step SC5 that the distance is one movement unit, the movement range restriction unit 24 ends the movement availability determination process without moving the cross section. When it is determined in step SC5 that the distance is not one movement unit, that is, two movement units or more, the movement range restriction unit 24 sets a position that is half the distance between the pre-designation cross-section and the post-designation cross-section to a new position. The cross-sectional position after the designation is set (step SC6), and the process moves to step SC2. If it is determined that the movement is possible in the second step SC3, that is, if it is possible to move to a position 0.5 times the initial movement distance, the position moves to a position 0.5 times.

  However, there is also a method of moving to the maximum movable distance. For example, it is determined by performing Step SC2 and Step SC3 whether or not it is possible to move from the initial moving distance to a position that is 0.75 times without moving to a position that is 0.5 times. If the position cannot be moved to the 0.75 times position, the position is moved to the 0.5 times position. Such a process is repeated, the maximum movable distance is specified, and the cross section is moved to the specified position.

  In comparative interpretation, the user moves the slider by operating the mouse of the operation unit 22 to designate the position of the reference cross section to be displayed. FIG. 12 is a diagram illustrating cross-sectional movement by cross-sectional tracking. As shown in FIG. 12, before the section is designated, images of the reference section KD1 and the comparison section HD1 are displayed. When the reference cross section is designated as the reference cross section KD2, the reference image generating unit 16 generates reference image data related to the reference cross section KD2. Then, the comparison image generation unit 18 applies a coordinate conversion formula to the designated reference section KD2, and calculates a comparison section HD2 that is anatomically identical to the designated reference section KD2.

The cross-section following process will be described using mathematical expressions. The reference cross section is expressed as r ′ = a · n ′ + i · i ′ + j · j ′. A character with a symbol “′” indicates a vector. The parameter a indicates the cross-sectional position (Z direction). The parameter “a” is sequentially changed by the user by the section designation operation. The parameter a in the reference section KD1 is a ₁ , and the parameter a in the reference section KD2 is a ₂ . The vector n ′ indicates the direction when changing the cross section. Typically, the vector n ′ indicates the Z direction orthogonal to the display cross section. A vector i ′ indicates the horizontal direction of the screen (X direction). The vector j ′ indicates the screen vertical direction (Y direction). The parameter i indicates the pixel position in the X direction on the display section. The parameter j indicates the pixel position in the Y direction on the display section. The equation of the comparison cross section is expressed as t ′ = f (r ′). f (r ′) is a coordinate conversion formula.

Using the above formula, the reference cross section KD1 is expressed as r ′ = a ₁ · n ′ + i · i ′ + j · j ′, and the comparison cross section HD1 has r ′ = f (r ′), r ′ = a ₁ · n ′ + i · i ′ + j · j ′. Similarly, the reference cross section KD2 is expressed as r ′ = a ₂ · n ′ + i · i ′ + j · j ′, and the comparison cross section HD2 is r ′ = f (r ′), r ′ = a ₂ · n ′ + i · i ′ + j · j ′.

For example, when calculating the comparison section HD1 corresponding to the reference section KD1, the comparison image generation unit 18 applies the pixels in the plane r ′ = a ₁ · n ′ + i · i ′ + j · j ′ to the comparison volume data. The pixel values of the pixels at r ′ = f (r ′) and r ′ = a ₁ · n ′ + i · i ′ + j · j ′ on the comparison volume data are assigned. For example, the comparison image generation unit 18 sets the pixel value of the coordinates (100, 100, a ₁ ) on the comparison volume data corresponding to the coordinates (100, 100, a ₁ ) on the reference section KD1 to r ′ = f (R ′), a pixel value on the comparison volume data at a position of r ′ = a ₁ · n ′ + 100 · i ′ + 100 · j ′ is assigned.

  Next, a method for displaying a substantially anatomically matching cross-section with a simple operation when the cross-section following process is not realized with the accuracy desired by the user will be described. In this method, the parameter s is added to the coordinate conversion formula f (r) calculated in the registration process. This parameter s is called manual shift. When the manual shift s is used, the reference cross section is r ′ = a · n ′ + i · i ′ + j · j ′, and the comparison cross section is t ′ = f (r ′), r ′ = (a + s) · n ′. + I · i ′ + j · j ′.

FIG. 13 is a diagram showing cross-sectional movement when the manual shift s is used. In the case of s = 0 shown in the upper part of FIG. 13, the reference cross section KD1 at the cross sectional position a ₁ is r ′ = a ₁ · n ′ + i · i ′ + j · j ′. The comparison section HD1 corresponding to the reference section KD1 is t ′ = f (r ′) and r ′ = a ₁ · n ′ + i · i ′ + j · j ′. When the manual shift s in this state is set to s ≠ 0, for example, s = _{s 1,} reference cross section KD1 does not change, compared sectional HD1 is, s from a cross-sectional position _{a 1} while maintaining the shape of the comparison section HD1 only ₁ move. The comparison cross section HD1 in the case of s = s ₁ is t ′ = f (r ′), r ′ = (a ₁ + s ₁ ) · n ′ + i · i ′ + j · j ′.

The manual shift s and the cross-sectional position a can be individually changed via the operation unit 22. 14, from the state of FIG. 13 is a diagram showing the reference section as compared cross section when changing the cross-sectional position a to a _4. As shown in FIG. 14, the reference cross KD4 in the cross-section position _{a 4} is a _{r'= a 4 · n'+ i} · i'+ j · j'. Following this change in section, the comparison section HD3 moves a ₄ -a ₁ and is updated to the comparison section HD4. The comparison cross section HD4 is t ′ = f (r ′), r ′ = (a ₄ + s ₁ ) · n ′ + i · i ′ + j · j ′. That is, when the cross-sectional position of the reference image is changed, the cross-sectional position of the comparative image is displayed following the reference cross-section while maintaining the manual shift value.

  FIG. 15 is a diagram illustrating a mouse operation pattern when the cross-sectional position a and the manual shift s are changed. As shown in FIG. 15, an image whose cross section is changed is selected by placing the cursor on the reference image or the comparison image displayed on the display unit 20. By performing a predetermined mouse operation in the selected state, the cross-sectional position a and the manual shift s of the selected image are changed. When the cross-sectional position a is changed, the comparative image follows the reference image. When the manual shift s is changed, only the cross section of the comparative image moves. When a + s is stored and a and s are changed, only the cross-sectional position of the reference image moves.

  The optimum operation pattern is the operation method 1. In the operation method 1, when a drag operation is performed on the reference image, the cross-sectional position a is changed, and the comparative cross-section follows the reference cross-section. When a drag operation is performed on the comparison image, the manual shift s is changed, and only the comparison section is changed.

  Although the operation method 1 and the operation method 2 can change the two values of the cross-sectional position a and the manual shift s, the cross-sectional change for tracking is performed on the reference image, and the correction of the curved surface is performed on the comparative image. To be unified. Further, since the same function is assigned to the drag operation and the wheel operation, it is possible to easily master the operation of changing the user cross section. Even when a cross-section change with a slider is added, it is only necessary to assign the same function, and the operation method is very easy to understand.

  When the user double-clicks on the image, the operation unit 26 is configured to clear the manual shift s to zero. By providing the manual shift s clearing means, it is possible to display the same anatomical section immediately after the user adjusts the value of the manual shift s so that the same section is displayed.

  In each of the above two cross-section tracking methods, a coordinate conversion formula is applied to the entire cross-section. That is, when the coordinate conversion formula calculated by the registration process is t ′ = f ′ (r ′), the comparison cross section is t ′ = f ′ (r ′), r ′ = a · n ′ + i · i ′. It is assumed that the calculation is performed by + j · j ′. The cross-section following method described below is a method for calculating a cross section having a planar shape by applying a coordinate conversion formula t ′ = f ′ (r ′).

First, the reference attention point P _r ′ is set on the reference cross section via the operation unit 22. The comparative attention point P _t ′ on the comparative section corresponding to the reference attention point P _r ′ is P _t ′ = f (P _r ′). The coordinate value on the reference cross section passing through the reference attention point P _r ′ is _r ′ = P _r ′ + a · _n ′ + i · i ′ + j · j ′.

As a coordinate conversion formula for the comparison cross section, g ′ ( _r ′) = Rf ′ ( _r ′) + P _t ′ −Rf ′ (P _r ′) is used. The comparison cross section is t ′ = g ′ (r ′), r ′ = a · n ′ + i · i ′ + j · j ′, that is, t ′ = Rf ′ ( _r ′) + P _t ′ −Rf ′ (P _r ′), R ′ = a · n ′ + i · i ′ + j · j ′. R is a coordinate transformation matrix representing rotation. The value of R may be a constant value, but may be determined from the gradient of f ′ ( _r ′) in P _r ′. If the latter method is used, the amount of rotation from the reference cross section to the comparative cross section at the designated point of interest can be calculated, so that the accuracy of the comparative cross section is improved as compared with the former case. g ′ (r ′) is a coordinate conversion formula composed only of rotation and translation. Therefore, when the comparative cross section is calculated by applying the coordinate conversion formula g ′ (r ′) to the reference cross section having a planar shape, the comparative cross section is not deformed and has a planar shape. Further, when the coordinate conversion equation g ′ (r ′) is used, neither enlargement nor reduction is performed. Further, P _r ′ on the reference cross section is mapped to g ′ (P _r ′) = Rf ′ (P _r ′) + P _t ′ −Rf ′ (P _r ′) = P _t ′. The reference attention point P _r ′ is included, and the comparative cross section includes the comparison attention point P _t ′.

Since P _t ′ = f ′ (P _r ′), the reference attention point P _r ′ and the comparison attention point P _t ′ are two points associated with each other by the registration process. In the vicinity of the comparative attention point P _t ′, the positional deviation between g ′ (r ′) and f ′ (r ′) is not large, so the vicinity of the comparative attention point P _t ′ is associated by the registration process. Points close to the point are included in the reference cross section and the comparison cross section.

FIG. 16 is a diagram showing cross-sectional movement when the coordinate conversion formula g ′ (r ′) is used. As shown in FIG. 16, the reference cross section KD1 includes a point of interest P _r ′. When the coordinate conversion formula g ′ ( _r ′) is applied to the reference section KD1, a comparison section HD5 including a point P _t ′ corresponding to the attention point P _r ′ is calculated. The comparison cross section HD5 is not deformed.

  When the same cross-section calculation method without deformation is adopted, the point of interest is configured to be specified by the user by double-clicking on the reference image or the comparison image. For example, when a double click is performed on a point on an abnormal region such as a tumor inside the lung, a point of interest is set at that point. In the comparison image, a surface that does not include deformation is displayed. At this time, the set attention point and its vicinity are displayed as points that are very close to the same point associated by the registration process. Therefore, in practice, both images can be regarded as anatomically identical. Unlike the case with deformation, since the image is not deformed, enlarged or reduced, the size can be compared correctly. When diagnosing a tumor, changes in morphological information such as shape and size are important information. For this reason, the display of the same cross section that is not deformed, enlarged, or reduced as described above is useful for diagnosis of an isolated lesion such as a tumor.

  Even when the same cross-section calculation method without deformation is adopted, the registration process itself takes into account deformation, so the effect of being able to perform high-precision alignment in consideration of the deformation of the chest due to breathing etc. Absent.

  The type of the same cross section (with / without deformation) is preferably configured so that the user can be switched by operating a button on the screen.

  FIG. 17 is a diagram showing mark patterns representing the type of the same cross section (with / without deformation) and the presence or absence of manual shift s. For example, the mark M is preferably displayed so as to be superimposed on the image as shown in FIG. A mark M shown in FIG. 18 indicates that there is no manual shift (s = 0) and no deformation.

  Since the user is gazing at the image at the time of image interpretation, it is important to display it superimposed on the image. By displaying a mark that can distinguish whether there is deformation or not, the user can clearly determine the type of the same cross section on the screen. Therefore, it is possible to prevent misdiagnosis caused by comparing and diagnosing the shape and size in a state with deformation. In addition, by displaying a mark that can distinguish the presence or absence of manual shift. You can always check whether the displayed cross section is a manually shifted cross section or the same anatomical cross section.

  With the above configuration, the image display device 1 displays two sets of images, that is, a reference image and a comparative image. When coordinate transformation (such as deformation) is applied to at least one of the images, the image display device 1 reproduces both images. The range of cross-sectional positions can be limited so that the constituent regions are included. As a result, a state in which the reconstruction area is not displayed on the screen can be prevented, and the occurrence of anxiety for the user can be prevented.

  In addition, the image display device 1 sets a small number of evaluation points in the volume data, calculates where the evaluation points are in the reference image and the comparison image, determines the positional relationship with the cross section, The range of the configuration area and the range of the comparative reconstruction area are specified, and the common range of the specified range is set as the limit range. Therefore, the limit range can be determined in consideration of parallel movement and deformation of the two sets of images. In addition, since the limit range determination process is performed with a small number of evaluation points, the process can be performed in a short time. Therefore, the cross-section movement restriction process can be realized without hindering the user's cross-section movement operation.

  The image display device 1 calculates and displays a cross section obtained by adding a manual shift s to the same anatomical cross section calculated by the registration process. Therefore, even when a position shift occurs in the same cross section calculated by the registration process, a cross section that can be regarded as the same by the user can be designated by a simple operation of changing the manual shift s. Further, by providing a means for storing the manual shift s, even if the other cross-section is changed after the manual shift s is adjusted, the cross-section that can be considered to be the same can be displayed. Since the deformation amount and the cross-sectional position of the display cross-section serving as the adjustment reference are determined by the registration process, there is a possibility that a minute error is included. However, since the approximate amount of deformation and the amount of translation are reflected, it is possible to designate substantially the same anatomical section by adjusting the manual shift s. Therefore, even when a position shift occurs in the same cross section calculated by the registration process, the substantially same cross section can be displayed by a simple operation. Therefore, the user can correctly determine and interpret an image change.

  Thus, according to the present embodiment, it is possible to improve the interpretation accuracy in the image display apparatus 1 for comparative interpretation that displays a plurality of images simultaneously.

  In the present embodiment, the two images of the reference image and the comparison image are comparatively interpreted. However, the present embodiment is not limited to this. For example, the storage unit 12 may store a plurality of comparison volume data files having different scan times, and the display unit 20 may display a reference image and a plurality of comparison images based on the plurality of comparison volume data files in parallel. Good.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The figure which shows the structure of the image display apparatus which concerns on embodiment of this invention. The figure which shows the structure of the volume data which concern on this embodiment. The figure which shows an example of the display image displayed by the display part of FIG. The figure which shows the flow of the process for the comparative interpretation by the image display apparatus of FIG. 5 is a flowchart according to the restriction range determination process of FIG. The figure which shows the reference | standard evaluation point and a comparative evaluation point set in step SA1 and step SA2 of FIG. FIG. 6 is a diagram illustrating a distance between an initial cross section and an evaluation point calculated in step SA3 in FIG. 5. The figure which shows the restriction | limiting range determined in step SA5 of FIG. The flowchart of the application example of the setting method of the evaluation score based on step SA1 of FIG. FIG. 4 is a flowchart of limit range determination processing different from FIG. 3. The figure for demonstrating the determination process of step SC3 of FIG. The figure which shows an example of the cross-section tracking display which concerns on the range restriction | limiting display process of FIG. The figure which shows the cross-section movement at the time of using the manual shift s in the cross-section follow-up display which concerns on the range restriction | limiting display process of FIG. From the state of FIG. 13, showing the reference section as compared cross section when changing the cross-sectional position a in a ₄ FIG. The figure which shows the operation pattern of the mouse | mouth in the case of changing the cross-sectional position a and the manual shift s based on the restriction | limiting display process of FIG. The figure which shows the cross-section movement in the case of using coordinate conversion type | formula g '(r') in the cross-section follow-up display which concerns on the range restriction | limiting display process of FIG. The figure which shows the pattern of the mark showing the presence or absence of the type | mold (with deformation | transformation / non-deformation) manual shift s of the same cross section concerning the restriction | limiting display process of FIG. The figure which shows the example of a display of the mark shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image display apparatus, 12 ... Memory | storage part, 14 ... Coordinate transformation formula calculation part, 16 ... Reference | standard image generation part, 18 ... Comparison image generation part, 20 ... Display part, 22 ... Operation part, 24 ... Movement range restriction | limiting part, 26 ... Control unit

Claims (19)

A storage unit for storing first volume data including a first reconstruction area and second volume data including a second reconstruction area, which have different scan times;
A cross-section designating unit for designating the position of the first display cross-section for the first volume data;
A first cross-sectional image generating unit that generates data of a first cross-sectional image related to the first display cross-section at the designated position from first volume data;
A second cross-sectional image generator for generating second cross-sectional image data relating to a second display cross-section having a position anatomically substantially the same as the position of the first display cross-section from second volume data;
A display unit for displaying the generated first slice image and second slice image;
A range limiting unit that limits a specifiable range of the position of the first display cross section based on the range of the first reconstruction area and the range of the second reconstruction area;
An image display device comprising:   The range limiting unit includes a range including both the range of the first reconstruction area and the range of the second reconstruction area, or the range of the first reconstruction area and the range of the second reconstruction area. The image display apparatus according to claim 1, wherein a range including at least one of the ranges is set as the specifiable range.   The range limiting unit determines whether or not at least a part of the second reconstruction area is included in the second cross-sectional image at the specified position, and determines the specifiable range based on the determination result. The image display device according to claim 1, wherein the image display device is limited. A plurality of first anatomically characteristic feature points included in the first volume data, and a plurality of second anatomically identical second feature points included in the second volume data. A conversion formula calculation unit that calculates a first coordinate conversion formula between the first volume data and the second volume data based on the feature points;
The second slice image generation unit calculates the second display slice having a curved surface shape by applying the calculated first coordinate conversion formula to the first display slice, and based on the calculated second display slice. Generating data of the second cross-sectional image
The image display device according to claim 1.   The second cross-sectional image generation unit calculates the second display cross section by applying the first coordinate conversion formula to the first display cross section every time the position of the first display cross section is changed. The image display device according to claim 4, characterized in that: The cross section designating unit designates a position separated by a desired distance from the position of the second display cross section before the position designation as the position of the second display cross section after the position designation,
The second cross-sectional image generation unit calculates a second display cross-section after the position designation having the same shape as the second display cross-section before the position designation, and the second cross-sectional image after the calculated position designation Generating data,
The image display device according to claim 4. The conversion formula calculation unit calculates a second coordinate conversion formula by adding a parameter representing the distance to the first coordinate conversion formula,
The second cross-sectional image generation unit applies the calculated second coordinate conversion formula to the first display cross-section after position designation to calculate the second display cross-section after position designation.
The image display device according to claim 6.   The image display apparatus according to claim 6, further comprising a reset unit that sets the distance to zero. The display unit displays on the screen a mark indicating whether or not the distance value is zero.
The image display device according to claim 6. Includes anatomically identical second target point to a first target point on the first display section, the third coordinate conversion formula for calculating the second display section having a vertical planar shape slice direction further comprising a you calculate conversion formula calculating unit,
The second cross-sectional image generation unit applies the third coordinate conversion formula to the first display cross section to calculate a second display cross section having the planar shape;
The image display device according to claim 1. A plurality of first anatomically characteristic feature points included in the first volume data, and a plurality of second anatomically identical second feature points included in the second volume data. A first coordinate conversion formula between the first volume data and the second volume data based on a feature point, or a second attention anatomically identical to the first attention point on the first display section A conversion formula calculation unit that selectively calculates a third coordinate conversion formula for calculating a second display cross section including a point and having a planar shape perpendicular to the slice direction;
Or using said first coordinate transformation equation, or, further comprising a selection unit that selects whether to use the third coordinate transformation equation,
The display unit displays a mark on the screen according to the selection by the selection unit .
The image display device according to claim 1 . The display unit displays a slider and a moving range of the slider corresponding to the range of the first reconstruction area,
The cross-section specifying unit specifies the position of the first display cross-section according to the position of the slider within the moving range.
The image display device according to claim 1.   The image display device according to claim 1, wherein the cross-section specifying unit specifies the position of the first display cross-section according to a rotation amount of a wheel provided in a mouse.   The image display device according to claim 1, wherein the cross-section specifying unit specifies the position of the first display cross-section in accordance with a movement amount of a mouse drag operation. The range limiter is
A plurality of first evaluation points are set on an upper end surface and a lower end surface of the first volume data or the first reconstruction area;
A plurality of second evaluation points that are anatomically identical to the plurality of first evaluation points are set in the second volume data;
Calculating a distance between each of the set second evaluation points and the second display section;
Determining a range of the second reconstruction region based on the calculated plurality of distances;
The image display device according to claim 1. The range limiter is
Setting a plurality of first evaluation points in the biological region included in the first reconstruction region;
A plurality of second evaluation points that are anatomically identical to the plurality of first evaluation points are set in the second volume data;
Calculating a distance between each of the set second evaluation points and the second display section;
Determining a range of the second reconstruction region based on the calculated plurality of distances;
The image display device according to claim 1. A storage unit for storing first volume data including a first reconstruction area and second volume data including a second reconstruction area, which have different scan times;
A first cross-sectional image generating unit that generates data of a first cross-sectional image related to a first display cross-section of the first volume data from the first volume data;
A conversion formula calculation unit for calculating a first coordinate conversion formula for calculating a second display cross section of the second volume data, which has an anatomically identical position with the position of the first display cross section;
A second display cross section calculating unit that calculates the second display cross section by applying the calculated first coordinate conversion formula to the first display cross section;
A second cross-section position changing unit that changes the position of the second display cross-section while maintaining the calculated shape of the second display cross-section;
A second cross-sectional image generator that generates data of the second cross-sectional image related to the second display cross-section after the change is made from the second volume data;
A display unit for displaying the generated first slice image and second slice image;
An image display device comprising: The conversion formula calculation unit calculates a second coordinate conversion formula by adding a parameter indicating the amount of change to the one coordinate conversion formula,
The second display cross section calculating unit applies the calculated second coordinate conversion formula to the first display cross section to calculate a hand second display cross section;
The image display device according to claim 17.   18. The image display device according to claim 1, wherein the second volume data is a plurality of volume data files having different scan times.

Images