JP2023039760A - Image processing device, image processing method and program - Google Patents

Abstract

An object of the present invention is to improve the visibility of a differential image between three-dimensional images.
The image processing device includes a slab that includes a predetermined cross section of a three-dimensional image to be displayed and has a thickness along an axial direction that intersects the cross section as a slab thickness. A control unit is provided for generating a slab image in which the pixel values of the directions are projected onto the cross section. The control unit obtains the pixel value of each pixel of the slab image by synthesizing the maximum value and the minimum value of the pixel values of each pixel in the slab corresponding to each pixel in the axial direction.
[Selection diagram] Fig. 1

Description

The present invention relates to an image processing device, an image processing method, and a program.

Patent Literature 1 discloses a technique for visualizing changes in lesions and the like in the medical field by presenting a user with a differential image between three-dimensional images obtained by imaging with various modalities.

JP-A-2018-33698

In the technique disclosed in Patent Document 1 for visualizing changes such as lesions, there may be cases where changes included in the difference image between three-dimensional images are overlooked.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an image processing technique capable of improving the visibility of a difference image between three-dimensional images.

An image processing apparatus according to one aspect of the present invention has the following configuration. That is, the image processing apparatus includes a slab that includes a predetermined cross section of a three-dimensional image to be displayed and has a thickness along an axial direction that intersects the cross section as a slab thickness. An image processing apparatus having control means for generating a slab image in which pixel values are projected onto the cross section, wherein the control means converts the pixel value of each pixel of the slab image into an image in the slab corresponding to each pixel. It is characterized in that it is obtained by synthesizing the maximum value and the minimum value of the pixel values of each pixel in the axial direction.

ADVANTAGE OF THE INVENTION According to this invention, the visibility of the difference image between three-dimensional images can be improved.

1 is a diagram showing the configuration of an image processing system including an image processing apparatus according to a first embodiment; FIG. FIG. 4 is a diagram showing the functional configuration of a control unit of the image processing apparatus; 4 is a flowchart showing an example of a processing procedure of an image processing apparatus; FIG. 4 is a diagram schematically illustrating a slab image; FIG. 4 is a diagram schematically explaining a slab image and pixel values in each slice; FIG. 4 is a diagram schematically explaining a differential slab image;

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. In addition, the following embodiments do not limit the invention according to the scope of claims. Although multiple features are described in the embodiments, not all of these multiple features are essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant description is omitted.

[First embodiment]
The image processing apparatus according to this embodiment is an apparatus that performs display control for generating a difference image between two three-dimensional images (three-dimensional medical images) and displaying the generated difference image on a display unit. The configuration and processing of this embodiment will be described below with reference to FIG.

FIG. 1 is a diagram showing the configuration of an image processing system 10 including an image processing apparatus 100 according to the first embodiment. The image processing system 10 includes an image processing apparatus 100, a network 120, and a data server 130 as its functional configuration. The image processing apparatus 100 is communicably connected to the data server 130 via the network 120 . The network 120 includes, for example, a LAN (Local Area Network) and a WAN (Wide Area Network).

The data server 130 is a picture archiving and communication system (PACS) that holds and manages medical images and information associated with the medical images. The image processing apparatus 100 can acquire medical images held in the data server 130 via the network 120 . The data server 130 receives and stores images captured by medical imaging devices (modalities), and transmits images to each device in response to requests from the devices connected to the network 120 . It also has a database capable of storing various data associated with the received image along with the image.

In the following description, the data server 130 stores, as a plurality of 3D images, a plurality of 3D images (medical images) obtained by previously imaging a subject under different conditions (different modalities, imaging modes, dates and times, body positions, etc.). image) is retained. In this embodiment, images captured by an X-ray CT apparatus will be described as an example of a plurality of 3D images, but 3D images may be captured by other modalities. The modality includes, for example, an MRI apparatus, a SPECT apparatus, a PET apparatus, etc., in addition to the X-ray CT apparatus. image).

Moreover, when the image processing apparatus 100 generates a difference image between two three-dimensional images, the two three-dimensional images to be processed may be any combination of images. For example, images may be taken at the same time using different modalities or different imaging modes. For follow-up observation, the images may be images of the same subject taken in the same modality and in the same body position at different dates and times.

The image processing device 100 is a device that performs image processing according to the embodiment. The image processing apparatus 100 is an apparatus that generates a difference image between two three-dimensional images and displays it on the display unit 150, and functions as a terminal apparatus for image interpretation operated by a user such as a doctor. The image processing apparatus 100 includes a communication IF (Interface) 111 (communication section), a ROM (Read Only Memory) 112 , a RAM (Random Access Memory) 113 , a storage section 114 and a control section 115 . The image processing device 100 is connected to the instruction section 140 and the display section 150 .

The communication IF 111 (communication unit) is configured by a LAN card or the like, and realizes communication between an external device (for example, the data server 130 or the like) and the image processing apparatus 100 . The ROM 112 is configured by a non-volatile memory or the like, and stores various programs. The RAM 113 is composed of a volatile memory or the like, and temporarily stores various kinds of information as data. The storage unit 114 is configured by an HDD (Hard Disk Drive) or the like, and stores various kinds of information as data.

The instruction unit 140 includes a GUI (Graphical User Interface) such as a keyboard, mouse, and touch panel, and inputs instructions from a user (for example, a doctor) to the image processing apparatus 100 . An image to be processed is input to the image processing apparatus 100 according to an instruction from the user who operates the instruction unit 140 . Note that the image selection may not be based on the user's instruction, and for example, the control unit 115 of the image processing apparatus 100 may automatically select the image to be processed based on a predetermined rule.

FIG. 2 is a diagram showing a functional configuration of the control unit 115. As shown in FIG. The control unit 115 is configured by a CPU (Central Processing Unit) or the like, and controls the processing in the image processing apparatus 100 as a whole. The control unit 115 includes an input image acquisition unit 101, a difference image acquisition unit 103, and a display control unit 105 as its functional configuration.

The input image acquisition unit 101 acquires a reference image and a floating image as images to be processed from the data server 130 via the communication IF 111 (communication unit) and the network 120 . In the following description, medical image data that serves as a reference for alignment is referred to as a standard image (hereinafter referred to as a reference image), and medical image data that is aligned toward the reference image is referred to as a comparison image (hereinafter referred to as a floating image). . Then, the difference image acquisition unit 103 generates a difference image between the reference image and the floating image as an image to be processed. The display control unit 105 generates an image to be displayed on the display unit 150 and controls the display of the generated image.

The display unit 150 is composed of arbitrary devices such as an LCD and a CRT, and displays images and various information to the user. Specifically, the reference image acquired from the image processing apparatus 100 and the floating image are displayed. Also, the difference image generated by the image processing apparatus 100 is displayed.

Each component of the image processing apparatus 100 described above functions according to a computer program. For example, the control unit 115 (CPU) reads and executes a computer program stored in the ROM 112 or the storage unit 114 using the RAM 113 as a work area, thereby realizing the functions of each component. Note that some or all of the functions of the constituent elements of the image processing apparatus 100 may be realized by using a dedicated circuit. Also, some functions of the components of the control unit 115 may be realized by using a cloud computer.

For example, an arithmetic device located at a different location from the image processing device 100 is communicably connected to the image processing device 100 via the network 120, and data is transmitted and received between the image processing device 100 and the arithmetic device. The functions of the components of 100 or controller 115 may be implemented.

Next, an example of processing of the image processing apparatus 100 in FIG. 1 will be described with reference to FIG. FIG. 3 is a flow chart showing an example of the processing procedure of the image processing apparatus 100. As shown in FIG. In this embodiment, a CT image of a subject is used as an example to describe processing for obtaining a difference image between two three-dimensional images, but this embodiment can also be applied to images obtained by other modalities.

(S1010: Acquisition of input image)
In step S1010, when the user instructs acquisition of two images (a first image and a second image) via the instruction unit 140, the input image acquisition unit 101 receives a plurality of images specified by the user from the data server 130. Get the reference image and the floating image as images (image data) of Then, the obtained reference image and floating image are output to the difference image obtaining unit 103 and the display control unit 105 .

(S1020: Acquisition of difference image)
In step S1020, the difference image obtaining unit 103 generates a difference image between the reference image obtained in step S1010 and the floating image. First, of the two images (reference image and floating image) acquired from the input image acquiring unit 101, the difference image acquisition unit 103 performs deformation alignment of one (reference image) of the other (floating image). . For deformation registration, for example, known deformation registration processing such as FFD (Free-Form Deformation) method or LDDMM (Large Deformation Diffeomorphic Metric Mapping) method can be applied. Any such deformed registration shall preserve the structure of the target region in the medical image data.

The difference image acquisition unit 103 calculates the pixel position on the floating image corresponding to each pixel on the reference image by the deformation alignment process (acquires deformation information (deformation information) indicating the corresponding pixel position between the images). be able to. The pixel position of the pixel in the floating image corresponding to each pixel forming the reference image is used as corresponding pixel position information.

Based on the deformation information between the reference image and the floating image, the difference image acquisition unit 103 subtracts the pixel value of the position on the floating image associated with that position from the pixel value of each position of the reference image. A difference image can be obtained by

Note that when the difference image is stored in the data server 130 in advance, the process of generating the difference image based on the deformation information by the deformation position alignment is skipped, and the difference image stored in the data server 130 is read and acquired. It may be configured to Further, the image processing apparatus 100 does not necessarily have a function of generating a differential image, and the differential image obtaining unit 103 may be configured to obtain a differential image stored in the data server 130 . In this case, the processing of the input image acquisition unit 101 performed in step 1010 is not necessarily required. That is, for the purpose of observing only the difference image, it is not necessary to input either the reference image or the floating image. Moreover, for the purpose of comparing and observing the reference image and the difference image, it is not necessary to input the floating image.

(S1030: Display Image Generation and Display Control)
In step S1030, the display control unit 105 acquires a three-dimensional display target image (reference image, floating image, difference image) from the input image acquisition unit 101 and the difference image acquisition unit 103, and displays the acquired display target image on the display unit. 150 is displayed. Further, the display control unit 105 generates an image to be displayed on the display unit 150 based on the images obtained from the input image obtaining unit 101 and the difference image obtaining unit 103, and controls the display of the generated image on the display unit 150. conduct. The three-dimensional image to be displayed includes a difference image that indicates the difference between a standard image (reference image) that serves as a reference for alignment and a comparative image (floating image) that is aligned toward the standard image.

Here, the display control unit 105 has a function that a general medical image viewer has, and displays an arbitrary two-dimensional tomographic image in a reference image or a floating image according to a user's instruction via the instruction unit 140. It has a function (slice display function) of acquiring (cutting out) a slice image (interested section) and displaying the acquired slice image on the display unit 150 .

Further, the display control unit 105 acquires (cuts out) a slice image (differential slice image) of a differential image (at the same cross-sectional position as the cross section of interest) corresponding to the cross section of interest of the reference image from the differential image, and obtains (cuts out) the acquired differential slice. It has a function of displaying an image on the display unit 150 .

At this time, a linked display mode may be provided in which the cross section of interest of the reference image and the corresponding cross section of the differential image (differential slice image) are displayed side by side on the display unit 150 . Note that the cross section of interest can be specified according to the user's instruction via the instruction unit 140. For example, a cross section (Axial cross section), a coronal cross section (Coronal cross section) in an X-ray CT image can be specified. cross section), sagittal cross section, or any other cross section.

In addition, the display control unit 105 has a function (slab display function) to generate a slab image, which will be described later, for each of the reference image, the floating image, and the difference image, and display the slab image on the display unit 150 according to the user's instruction. ). In the linked display mode in which the cross-section of interest in the reference image and the cross-section of interest in the difference image are displayed side by side on the display unit 150, the display control unit 105 displays the cross-section of interest in the reference image in a slab. Display control is performed so that slabs are displayed with the same slab thickness. When displaying the slab image of the slab including the cross section of interest extracted from the standard image (reference image), the display control unit 105 displays the slab image of the slab including the corresponding cross section of the difference image corresponding to the cross section of interest with the same slab thickness. Perform display control to display with .

Here, the slab image is an image generated by setting a "slab" having a predetermined thickness (slab thickness) in the cross section of interest in the image space and projecting the pixels in the slab onto the cross section of interest. is. In other words, the slab image is an image obtained by consolidating (projecting) pixel values of pixels at corresponding positions in images of several slices before and after the cross section of interest onto the cross section of interest.

FIG. 4 is a diagram for schematically explaining a slab image, where a cross section of interest _is S _z0 (z=z0 cross section), and n slices (S _z1 , S _z2 . _zn-1 , S _zn ) _are set, and n slices (S _z-1 , S _{z- 2 .} ) is set. As shown in FIG. 4, when considering n slices before and after the cross section S _z0 of interest, the slab thickness is 1+2n slices, which is the sum of the cross section S _z0 of interest and the n slices before and after the cross section of interest (=2n). .

FIG. 5 is a diagram schematically explaining a slab image and pixel values in each slice. S _z0 (z=z0 cross section) is a cross section of interest, two slices (S _z1 , S _z2 ) are set in the +Z direction with respect to the cross section of interest S _z0 , and two slices are set in the −Z direction with respect to the cross section of interest S _z0 ( S _z-1 , S _z-2 ) are set.

In FIG. 5, P ₀ indicates a pixel on the cross section S _z0 of interest, and P ₀ (x, y) indicates a pixel value at coordinates (x, y, z0). In slice S _z1 in the +Z direction, the pixel value at the position corresponding to pixel P ₀ in cross section S _z0 of interest is denoted by P ₁ (x, y), and in slice S _z2 , it corresponds to pixel P ₀ in cross section S _z0 of interest. The pixel value of the position is indicated as P ₂ (x,y). The same applies to the −Z direction. In the slice S _z−1 , the pixel value at the position corresponding to the pixel P ₀ in the cross section S _z0 of interest is denoted by P ₋₁ (x, _y ). A pixel value at a position corresponding to pixel P ₀ on cross section S _z0 is indicated as P ₋₂ (x, y).

As shown in FIG. 5, a cross section of interest and a slab with a slab thickness of 5 slices when two slices (=2×2) before and after the cross section of interest are designated. Then, each pixel value of the slab image can be obtained by aggregating (projecting) the pixel values of each pixel at corresponding positions in the plurality of slice images onto the cross section of interest. For example, _in the example of FIG. 5, each pixel value of the slab image is each pixel (P ₋₂ , P ₋₁ , P ₀ , P ₁ , P ₂ ) can be obtained by aggregating (projecting) the pixel values of the cross section S _z0 of interest.

Note that the slab thickness can be arbitrarily set by the user via the instruction unit 140 . Also, as shown in FIGS. 4 and 5, setting the target cross section _Sz0 at the center of the slab is only an example, and the upper end of the slab (for example, the +Z direction slab end in ) or the lower end (for example, the end of the slab in the -Z direction in FIGS. 4 and 5).

The display control unit 105 includes a predetermined cross section (interested cross section) of the three-dimensional display target image, and controls the thickness along the axial direction (for example, the Z axis in the examples of FIGS. 4 and 5) intersecting with the cross section. In a slab having a slab thickness, a slab image is generated by projecting pixel values in the axial direction of an image to be displayed onto a cross section. The display control unit 105 can generate a slab image of a reference image or a floating image using various types of image processing. For example, the display control unit 105 calculates the average value of pixel values, calculates the median value, obtains the maximum value, acquires the can be used.

A method of acquiring each pixel value of a slab image by acquiring the maximum value of each pixel value of a plurality of slice images is called Maximum Intensity Projection (MIP). Similarly, a method of acquiring each pixel value of a slab image by acquiring the minimum value of each pixel value of a plurality of slice images is called Minimum Intensity Projection (MinIP). The display control unit 105 can generate a slab image using maximum intensity projection (MIP) or minimum intensity projection (MinIP). The display control unit 105 can also create slab images using other calculation methods.

(Generation of slab image)
The display control unit 105 generates a slab image of the differential image (differential slab image) by the following process. That is, the display control unit 105 generates the difference slab image Slab _Z=Z0 (x, y) by the arithmetic processing of the following formula (1).

Here, the difference image obtaining unit 103 generates determination information for determining the image type of the image to be displayed when generating the difference image between the reference image and the floating image as the image to be processed. Then, when generating a slab image, the display control unit 105 determines the image type of the image to be displayed (reference image, floating image, difference image) based on the presence or absence of determination information. If there is no determination information, the display control unit 105 determines that the image type of the image to be displayed is a reference image or a floating image, and generates a slab image by the processing described above. On the other hand, if the determination information is present, the display control unit 105 determines that the image type of the image to be displayed is a difference image, and calculates a difference slab image Slab _Z=Z0 (x, y).

In the arithmetic processing of formula (1), the display control unit 105 calculates the pixel value of each pixel on the differential slab image. where I _sub represents the difference image. Also, I _sub (x, y, z') represents the pixel value at the coordinates (x, y, z') on the differential image. Slab _Z=Z0 indicates that a differential slab image is generated with the z=z0 cross section as the cross section of interest. Also, n is a parameter that defines the slab thickness.

FIG. 6 is a diagram schematically explaining a difference slab image. _A cross section of interest is I _subz0 (z=z0 cross section ₎ , and n slices (I _subz1 , _{I subz2 .} , n slices (I _subz-1 , I _subz-2 . . . I _subz-(n-1) , I _subz-n ) are set in the −Z direction with respect to

In the arithmetic processing of equation (1), max represents the maximum value function, min represents the minimum value function, and the maximum and minimum pixel values of each pixel within the search range (within the projection range) are obtained. represents

However, the maximum value function max has a constraint condition that the maximum value is 0 or more. That is, if the maximum value is 0 or less, the maximum value is set to 0. Similarly, the minimum value function min has a constraint that the minimum value be 0 or less. That is, if the minimum value is 0 or more, the minimum value is set to 0. This process is equivalent to the process of finding the maximum positive value and the minimum negative value.

The display control unit 105 calculates the pixel values of the differential slab image based on the maximum and minimum pixel values obtained in this way. That is, the display control unit 105 sets the pixel value of each pixel of the slab image (difference slab image) to the maximum pixel value of each pixel in the axial direction (slab thickness direction) in the slab corresponding to each pixel. Calculated by combining with the minimum value.

Note that in the first embodiment, in addition to the sum (addition) of the maximum and minimum pixel values as described in Equation (1), Arithmetic processing based on a weighted sum using an average value of the maximum and minimum values of pixel values and weighted maximum and minimum values of pixel values may be included.

For example, as shown in FIG. 6, when n slices (n slices set in the +Z direction, n slices set in the −Z direction) from the section of interest (I _subz0 ) are set as slabs, the display control unit 105 computes each pixel of the slab image (differential slab image) using the maximum and minimum pixel values of each pixel in the axial direction (slab thickness direction) within the slab corresponding to each pixel. Determine the pixel value of each pixel in the difference slab image.

More specifically, in the arithmetic processing of formula (1), the display control unit 105 sets z0−n≦z′≦z0+n as a search range centering on the z=z0 cross section. Then, when a plurality of slices within the search range (within the projection range) are defined as slabs, the display control unit 105 determines the axial direction (slab thickness direction) within the slab at the position corresponding to each pixel of the differential slab image. obtains the maximum and minimum pixel values of each pixel of . Then, the display control unit 105 obtains the pixel value of each pixel of the difference slab image by calculation using the maximum and minimum values of the obtained pixel values. The display control unit 105 obtains the pixel value of each pixel of the slab image by combining the maximum value and the minimum value by adding the maximum value and the minimum value.

It should be noted that the display control unit 105 can modify the arithmetic processing of equation (1) to generate the average value of the maximum and minimum values of the obtained pixel values as the pixel value of the differential slab image.

(weighted sum of maximum and minimum values)
The display control unit 105 can also generate a difference slab image Slab _Z=Z0 (x, y) by the arithmetic processing of the following equation (2). That is, the display control unit 105 can also generate a value obtained by synthesizing the maximum value and the minimum value of the [0] acquired pixel values as the pixel value of the difference slab image, according to the following equation (2). is.

The arithmetic processing of expression (2) corresponds to the weighted sum of the maximum value and the minimum value described in expression (1). The display control unit 105 obtains the pixel value of each pixel of the slab image by obtaining a weighted sum using weights for the maximum and minimum values. In the arithmetic processing of formula (2), I _sub represents a differential image, as in the arithmetic processing of formula (1). Also, I _sub (x, y, z) represents the pixel value at the coordinates (x, y, z) on the differential image. Slab _Z=Z0 indicates that a differential slab image is generated with the z=z0 cross section as the cross section of interest. Also, n is a parameter that defines the slab thickness, and represents generation of a differential slab image in which n slices before and after the cross section of interest (that is, z=z0 cross section) are slabs.

The display control unit 105 sets the weight using the first distance from the cross section of the pixel that gives the maximum value (cross section of interest) and the second distance from the cross section of the pixel that gives the minimum value (cross section of interest). The display control unit 105 sets the first distance or the second distance so that the weight increases as the cross section (the cross section of interest) approaches, and the first distance or the second distance moves away from the cross section (the cross section of interest). Set so that the weight becomes smaller according to

In the arithmetic processing of Expression (2), the weights (w_max and w_min) used for the weighted sum can be obtained as follows. That is, the first distance from the cross section of interest of the pixel that gives the maximum value in the maximum value function (hereinafter referred to as d_max) and the second distance from the cross section of interest of the pixel that gives the minimum value in the minimum value function (hereinafter referred to as d_min) to determine the weight. The display control unit 105 sets the weight of the weighted sum so that, for example, the weight of the pixel closer to the cross section of interest is increased, and the weight of the pixel farther from the cross section of interest is decreased. set to The weight is set so that the closer the first distance (d_max) and the second distance (d_min) to the cross section of interest (the closer they are to 0), the greater the weight. The weight is set smaller as the first distance (d_max) and the second distance (d_min) are farther from the section of interest.

Equation (3) is a calculation formula for the maximum weight, and Equation (4) is a calculation formula for the minimum weight.

w_max=2*d_min/(d_max+d_min) (3)
w_min=2*d_max/(d_max+d_min) (4)
Note that the weight setting method may be any method as long as the weight is set according to the above constraints. For example, it can be realized by preparing in advance a table of weights corresponding to combinations of distances (d_max, d_min). The display control unit 105 sets the first distance (d_max) from the cross section of interest to the pixel that gives the maximum value in the maximum value function, and the second distance (d_min) from the cross section of interest to the pixel that gives the minimum value in the minimum value function. , and the weight corresponding to the combination of the obtained distances (d_max, d_min) can be obtained by referring to the table. The display control unit 105 sets weights by referring to a table in which weights corresponding to combinations of the first distance and the second distance are stored in advance.

Note that the method of obtaining the weighted sum of the maximum value and the minimum value by the arithmetic processing of Equation (2) is just one example of the method of synthesizing the maximum value and the minimum value based on the distance from the cross section of interest. For example, comparing the first distance (d_max) from the cross section of interest of the pixel that gives the maximum value in the maximum value function and the second distance (d_min) from the cross section of interest of the pixel that gives the minimum value in the minimum function , the value (maximum value or minimum value) closer to the cross section of interest may be selected as the pixel value of the differential slab image.

When synthesizing the maximum and minimum pixel values weighted based on the distance from the cross section of interest, if either the maximum value or the minimum value is 0, that value does not exist. interpret and adopt the other value.

In the differential image, both positive and negative values are significant. Therefore, the maximum and minimum values in the slab are obtained by the above-described processing and synthesized to obtain the differential image can generate a slab image suitable for When each pixel value of the slab image is obtained based only on the pixel values (maximum pixel values) obtained by the maximum intensity projection method, the characteristics of the pixel values (negative values) that can be obtained by the minimum intensity projection method is not reflected in the pixel values of the slab image. In addition, when each pixel value of the slab image is obtained based only on the pixel value (minimum pixel value) obtained by the minimum intensity projection method, the pixel value (positive value) that can be obtained by the maximum intensity projection method will not be reflected in the pixel values of the slab image.

According to the present embodiment, image processing using pixel values (maximum pixel values) obtained by maximum intensity projection and pixel values (minimum pixel values) obtained by minimum intensity projection is performed to obtain a three-dimensional image. The visibility of the difference image between images can be improved.

As described above, the display control unit 105 can change the slab image generation method based on the image type of the image to be displayed. Note that the slab image generation method does not have to be automatically selected based on the image type, and the user may designate the generation method via the UI of the instruction unit 140 .

Note that the display control unit 105 may store the generated differential slab image in the data server 130 via the storage unit 114 of the image processing apparatus 100 or the network 120 in the process of step S1030. This allows any other medical image viewer to display the differential slab image. In this case, the image display in step S1030 may not necessarily be performed.

According to this embodiment, by generating a slab image suitable for a differential image, it is possible to improve the visibility of the differential image between three-dimensional images.

<Second embodiment>
In the first embodiment, the configuration for displaying the difference image on the display unit has been described. A configuration for displaying a superimposed image superimposed on the display unit 150 will be described.

The configuration of the image processing system 10 according to this embodiment is the same as that of the first embodiment. However, in the second embodiment, the processing performed by the display control unit 105 is partially different from the processing in the first embodiment. In the following description, only the configuration of the different portion will be described.

Also, the flowchart showing the overall processing procedure performed by the image processing apparatus 100 in this embodiment is the same as in the first embodiment. However, since part of the processing performed by the display control unit 105 in S1030 is different, only the difference from the first embodiment will be described.

(S1030: Display Image Generation and Display Control)
In step S1030, the display control unit 105 acquires a three-dimensional display target image (reference image, floating image, difference image) from the input image acquisition unit 101 and the difference image acquisition unit 103, as in the first embodiment. , control to display the acquired display target image on the display unit 150 . Further, the display control unit 105 generates an image to be displayed on the display unit 150 based on the images obtained from the input image obtaining unit 101 and the difference image obtaining unit 103, and controls the display of the generated image on the display unit 150. conduct. In this embodiment, the display control unit 105 further performs control to generate a superimposed image in which the difference image is superimposed on the reference image and display the superimposed image on the display unit 150 .

Here, the superimposed image is an image obtained by superimposing a difference image in which each pixel is colored based on the pixel value of the maximum value and the pixel value of the minimum value, on the reference image. When displaying a superimposed image in a slice (that is, when displaying a slice image obtained by cutting out a cross section of a part of the superimposed image), the display control unit 105 displays the slice image of the reference image in the corresponding differential image. Pixels with positive difference values are set to a first color (eg, blue), and pixels with negative difference values are set to a second color (eg, red). Then, the display control unit 105 displays an image in which a color with transparency corresponding to the magnitude of the absolute value of the difference value (which becomes more opaque as the absolute value of the difference value increases) is superimposed on the slice image of the reference image. It controls the display on the unit 150 .

On the other hand, when the superimposed image is displayed in a slab (that is, when the slab image of the superimposed image is displayed), the display control unit 105 generates a slab image of the reference image in the cross section of interest and a differential image of the corresponding cross section. A MIP slab image and a MinIP slab image are generated respectively. Here, the MIP slab image is a slab image based on the pixel values obtained by the maximum intensity projection method described above, and the MinIP slab image is a slab image based on the pixel values obtained by the minimum intensity projection method. is.

In the second embodiment, when combining the maximum and minimum pixel values, in addition to the combination described in the first embodiment, different display colors are set for the maximum and minimum pixel values. , a process of obtaining a mixture of the display color set to the maximum pixel value and the display color set to the minimum pixel value.

The display control unit 105 sets the first color (eg, blue) as the display color of each pixel in the MIP slab image, and sets the second color (eg, red) as the display color of each pixel in the MinIP slab image. set. The display control unit 105 can also change the shade of the display color according to the magnitude of the pixel value (absolute value) of each pixel. Then, the display control unit 105 mixes the first color (blue) and the second color (red) based on the pixel value of the corresponding pixel at the corresponding pixel position between the MIP slab image and the MinIP slab image. (eg purple). The display control unit 105 generates a superimposed image in which the mixed color of the first color (blue) and the second color (red) is superimposed on the slab image of the reference image, and controls the display unit 150 to display the superimposed image. conduct.

According to this embodiment, the pixel value of each pixel of the slab image is set to the maximum pixel value and the minimum pixel value, respectively, to visualize a mixture of different colors (first color and second color). This makes it possible to improve visibility.

(Other embodiments)
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in the computer of the system or apparatus reads and executes the program. It can also be realized by processing to It can also be implemented by a circuit (for example, ASIC) that implements one or more functions.

The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the claims are appended to make public the scope of the invention.

101: input image acquisition unit, 103: difference image acquisition unit, 105: display control unit

Claims (13)

In a slab that includes a predetermined cross section of a three-dimensional image to be displayed and has a thickness along an axial direction that intersects the cross section as a slab thickness, pixel values in the axial direction of the image to be displayed are projected onto the cross section. An image processing apparatus having a control means for generating a slab image obtained by:
The control means obtains the pixel value of each pixel of the slab image by synthesizing a maximum value and a minimum value of pixel values of each pixel in the slab corresponding to each pixel in the axial direction. image processing device. 2. The method according to claim 1, wherein said control means obtains a pixel value of each pixel of said slab image by combining said maximum value and said minimum value by adding said maximum value and said minimum value. Image processing device. The control means sets a weight using a first distance from the cross section of the pixel that gives the maximum value and a second distance from the cross section of the pixel that gives the minimum value, and based on the weight, the 3. The image processing apparatus according to claim 1, wherein a maximum value and a minimum value of pixel values are combined. The control means sets the weight so that the weight increases as the first distance or the second distance approaches the cross section, and the weight increases as the first distance or the second distance increases away from the cross section. 4. The image processing apparatus according to claim 3, wherein the weight is set to be small. 5. The image according to claim 3, wherein the control means sets the weight by referring to a table in which weights corresponding to combinations of the first distance and the second distance are stored in advance. processing equipment. 6. The control means determines the pixel value of each pixel of the slab image by determining a weighted sum using the weight for the maximum value and the minimum value. 1. The image processing apparatus according to claim 1. The control means compares a first distance from the cross section of the pixel giving the maximum value with a second distance from the cross section of the pixel giving the minimum value,
2. The image processing apparatus according to claim 1, wherein the value closer to the cross section out of the maximum value and the minimum value is selected as the pixel value of each pixel of the slab image. The image to be displayed includes a reference image that serves as a reference for alignment and a difference image between a comparison image that is aligned toward the reference image,
8. The image processing apparatus according to claim 1, wherein said control means generates said slab image based on said difference image. When displaying the slab image of the slab including the cross section of interest extracted from the reference image, the control means displays the slab image of the slab including the corresponding cross section of the difference image corresponding to the cross section of interest with the same slab thickness. 9. The image processing apparatus according to claim 8, wherein display control is performed so as to The control means performs control to display a superimposed image obtained by superimposing the difference image on the reference image on a display means,
10. The image according to claim 9, wherein the superimposed image is an image obtained by superimposing a difference image in which each pixel is colored based on the pixel value of the maximum value and the pixel value of the minimum value, on a reference image. processing equipment. The control means sets a first color as a display color of the maximum pixel value and sets a second color as a display color of the minimum pixel value,
11. The image processing according to claim 10, wherein control is performed to display on said display means a superimposed image in which a mixed color of said first color and said second color is superimposed on said slab image of said reference image. Device. In a slab that includes a predetermined cross section of a three-dimensional image to be displayed and has a thickness along an axial direction that intersects the cross section as a slab thickness, pixel values in the axial direction of the image to be displayed are projected onto the cross section. An image processing method for an image processing apparatus having control means for generating a slab image, comprising:
The control means has a step of obtaining a pixel value of each pixel of the slab image by synthesizing a maximum value and a minimum value of pixel values of each pixel in the slab corresponding to each pixel in the axial direction. An image processing method characterized by: A program that causes a computer to function as control means for the image processing apparatus according to any one of claims 1 to 11.

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