Program, image processing device and image processing method

Abstract

To provide a program capable of more appropriately evaluating a function of an organ.SOLUTION: A calculation part 3 calculates an area ratio which is a ratio of an area size corresponding to an organ of a subject in a planar image during natural respiration to the area size corresponding to the organ of the subject in the planar image during respiration. An enlargement part 4 generates an enlarged scintigraphy image obtained by enlarging an object area which is an area corresponding to the organ of the subject in a lung blood flow scintigraphy image based on the area image. A fusion unit 5 generates a fusion image obtained by overlapping an enlarged scintigraphy image and a chest CT image.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a program, an image processing device, and an image processing method. [Background technology]

[0002] In recent years, advances in software in the medical field have made it possible to create fusion images by superimposing three-dimensional CT (Computed Tomography) images, which are morphological images showing the morphology of a subject's organs, on three-dimensional nuclear medicine images (scintigraphy images) based on radiation from radiopharmaceuticals administered to the subject (see Patent Document 1). Because nuclear medicine images reflect functional areas in organs, doctors can use fusion images to more accurately evaluate or diagnose the state of organs.

[0003] For example, by using a fusion image that combines a chest CT image, which is a morphological image showing the morphology of the lung, with a lung perfusion scintigraphy image, which is a nuclear medicine image showing the blood flow in the lung, doctors can more accurately evaluate the functional areas of the lung. This can lead to appropriate treatment for conditions such as pulmonary thromboembolism, which are difficult to accurately evaluate or diagnose using only chest CT images or lung perfusion scintigraphy images. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-34779 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technique described in Patent Document 1 has a problem in that it is difficult to accurately superimpose a CT image of an organ, such as the lungs, whose size changes depending on the condition of the subject, on a nuclear medicine image.

[0006] For example, chest CT images and lung perfusion scintigraphy images are taken in different respiratory phases. Lung perfusion scintigraphy images require a long imaging time of approximately 20 minutes, as it is necessary to detect radiation from a radiopharmaceutical administered to the subject and generate a three-dimensional image. For this reason, the subject is scanned while breathing naturally. On the other hand, chest CT images can be generated in a short time, so the subject is scanned while taking a deep breath to capture a larger image of the lung area. Therefore, the size of the lungs captured in lung perfusion scintigraphy images differs from that in chest CT images, making it difficult to accurately overlay the chest CT images and lung perfusion scintigraphy images.

[0007] The lung region shown in a lung perfusion scintigraphy image represents the region of the entire lung where blood flow exists, while the lung region shown in a chest CT image represents the entire lung region. Therefore, if we simply enlarge the lung region shown in the lung perfusion scintigraphy image to match the lung region shown in the chest CT image, the region where blood flow exists in the lung in the lung perfusion scintigraphy image will be merged with the entire lung region in the chest CT image, making it difficult to generate an appropriate fused image.

[0008] An object of the present disclosure is to provide a program, an image processing device, and an image processing method that are capable of more appropriately evaluating organ function. [Means for solving the problem]

[0009] A program according to one aspect of the present disclosure causes a computer to implement an acquisition unit that acquires a three-dimensional anatomical image reflecting the morphology of an organ of a subject in a first state, a three-dimensional functional image reflecting the function of the organ of the subject in a second state, a first two-dimensional planar image reflecting the function of the organ of the subject in the first state, and a second two-dimensional planar image reflecting the function of the organ of the subject in the second state; a calculation unit that calculates the ratio of the size of an area corresponding to the organ in the first planar image to the size of an area corresponding to the organ in the second planar image; an enlargement unit that generates an enlarged image by enlarging a target area, which is an area corresponding to the organ in the functional image, based on the ratio; and a fusion unit that generates a fused image by superimposing the enlarged image and the anatomical image. [Effects of the Invention]

[0010] According to the present invention, it becomes possible to more appropriately evaluate organ function. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram illustrating a configuration of an image processing device according to an embodiment of the present disclosure. [Figure 2] FIG. 10 is a diagram illustrating an example of a process for calculating an area ratio. [Figure 3] 10 is a flowchart illustrating an example of the overall processing of the image processing device. [Figure 4] 10 is a flowchart illustrating an example of a calculation process. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0013] 1 is a block diagram showing the configuration of an image processing device according to an embodiment of the present disclosure. The image processing device 100 is configured, for example, by a computer system including a processor (computer) and a memory (neither of which is shown). In this case, the components and functions of the image processing device 100 described below are realized, for example, by the processor reading a computer program and executing the read program. The computer program can be recorded on a computer-readable recording medium 200. The recording medium 200 is, for example, a semiconductor memory, a magnetic disk, an optical disk, a magnetic tape, or a magneto-optical disk.

[0014] The image processing device 100 is also connected to an input / output device 101 and an auxiliary storage device 102. The input / output device 101 includes input devices such as a keyboard, a touch panel, and a pointing device that receive various pieces of information from a user who uses the image processing device 100, and output devices such as a display device and a printer that output various pieces of information to the user. The input / output device 101 may also include a network interface device that transmits and receives various pieces of information via a communication network such as the Internet. The auxiliary storage device 102 is a storage device that stores various pieces of information, such as a large-capacity storage device.

[0015] As shown in FIG. 1, the image processing device 100 includes an acquisition unit 1, a registration unit 2, a calculation unit 3, an enlargement unit 4, a fusion unit 5, and an output unit 6.

[0016] The acquisition unit 1 acquires medical images of a predetermined organ of a subject. In this embodiment, the predetermined organ is the lung, but may be another organ such as the liver or kidney that is affected by the subject's respiratory condition. The medical images include chest CT images, pulmonary perfusion scintigraphy images, and pulmonary perfusion planar images. In this embodiment, the medical images are stored in an auxiliary storage device 102, and the acquisition unit 1 acquires the medical images from the auxiliary storage device 102. However, the acquisition unit 1 may also acquire the medical images from a modality (not shown), which is an imaging device that captures an image of the subject and generates a medical image. Alternatively, the acquisition unit 1 may acquire the medical images via a communication network using the input / output device 101, or may store the acquired medical images in the auxiliary storage device 102.

[0017] A chest CT image is a three-dimensional morphological image that reflects the morphology of the lungs of a subject. The chest CT image is generated by imaging the subject using an X-ray CT device or the like. In this embodiment, the chest CT image is generated by imaging the subject in a deep inhalation state, which is a first state.

[0018] A pulmonary perfusion scintigraphy image is a three-dimensional functional image reflecting the blood flow (blood flow distribution) in the lungs, and is generated by imaging a subject using a nuclear medicine imaging device that detects radiation from the subject to which a radiopharmaceutical has been administered. The nuclear medicine imaging device is, for example, a SPECT (Single Photon Emission Computed Tomography) device or a PET (Positron Emission Tomography) device, and the pulmonary perfusion scintigraphy image is, for example, a SPECT image or a PET image. In this embodiment, the pulmonary perfusion scintigraphy image is a SPECT image generated by imaging a subject in the second state, that is, a state of spontaneous breathing. The radiopharmaceutical used in imaging this SPECT image is a radiopharmaceutical that shows a radioactivity distribution correlated with the pulmonary blood flow, and an example of this type of radiopharmaceutical is technetium macroaggregated human serum albumin ( 99 mTc) and others.

[0019] A pulmonary perfusion scintigraphy image includes a plurality of pixels arranged three-dimensionally and a pixel value for each pixel. The pixel value is determined according to the radiation emitted from the subject's tissue (e.g., blood), for example, according to the count value of the radiation.

[0020] Lung perfusion planar images are two-dimensional functional images reflecting pulmonary blood flow and are generated by imaging a subject using a nuclear medicine imaging device that detects radiation from the subject after administration of a radiopharmaceutical. Lung perfusion planar images include an inhalation planar image, which is a first planar image generated by imaging the subject in a deep inhalation state, and a spontaneous breathing planar image, which is a second planar image generated by imaging the subject in a spontaneous breathing state. Unlike three-dimensional lung perfusion scintigraphy images, lung perfusion planar images are two-dimensional images, and therefore can be generated in a short period of time. Therefore, similar to chest CT images, inhalation planar images can be generated by imaging the subject in a deep inhalation state.

[0021] Furthermore, the lung perfusion planar image can be generated using the same radiopharmaceutical and nuclear medicine imaging device as the lung perfusion scintigraphy image, so that imaging for the lung perfusion planar image and imaging for the lung perfusion scintigraphy image can be performed consecutively.

[0022] In this embodiment, the pulmonary blood flow planar image is a two-dimensional image along the coronal plane of the subject, and may be generated, for example, by superimposing a front image obtained by photographing the subject from the front and an inverted image of a back image obtained by photographing the subject from the back. Note that the front image, the back image, or an inverted image of either may be used as the pulmonary blood flow planar image.

[0023] The registration unit 2 generates a third planar image, which is a two-dimensional functional image reflecting the blood flow in the lungs, as a reference planar image from the pulmonary perfusion scintigraphy image acquired by the acquisition unit 1, and aligns the reference planar image with the pulmonary perfusion planar image. The reference planar image, like the pulmonary perfusion planar image, is a two-dimensional image along the coronal plane of the subject, and is generated, for example, by superimposing multiple slice images along the coronal plane of the subject that are included in the pulmonary perfusion scintigraphy image.

[0024] Registration is a process of correcting images so that corresponding locations in two images have the same coordinates. The method for registering the reference planar image and the pulmonary perfusion planar image is not particularly limited. For example, existing methods for registering two-dimensional images, such as the mean squared error (MSE) method, can be applied to register the reference planar image and the pulmonary perfusion planar image. In this process, the reference planar image and the pulmonary perfusion planar image are not scaled.

[0025] In this embodiment, the inhalation planar image and the natural breathing planar image are assumed to be registered in advance in the nuclear medicine imaging device. Therefore, the registration unit 2 can register either the inhalation planar image or the natural breathing planar image with the reference planar image, thereby enabling registration of both the inhalation planar image and the natural breathing planar image with the reference planar image.

[0026] The calculation unit 3 calculates an area ratio, which is the ratio of the size of the lung area in the planar image during inspiration to the size of the lung area in the planar image during natural breathing. The lung area is an area in the image that corresponds to the lungs, for example, an area consisting of pixels having pixel values ​​equal to or greater than a threshold. Note that since the planar image is a functional image that reflects pulmonary blood flow, the lung area in the planar image does not correspond to the entire lungs, but rather to a portion of the entire lung that has pulmonary function.

[0027] The lungs expand and contract (expand / contract) due to the up and down movement of the diaphragm located below the lungs, and therefore expand and contract generally along the body axis direction of the subject. For this reason, in this embodiment, the calculation unit 3 calculates the ratio of the size of the lung region in the body axis direction as the region ratio. More specifically, because the diaphragm is located below the lungs, the lower part of the lungs expands and contracts significantly, but the upper part does not expand and contract much. For this reason, in this embodiment, the calculation unit 3 calculates the region ratio of the lung region below a predetermined reference position in the body axis direction. Note that in this embodiment, the head side of the subject is defined as the upper side, and the foot side as the lower side.

[0028] The reference position may be set in advance or may be set by the user using the image processing device 100, but here, the calculation unit 3 calculates it based on the planar image during inspiration and the planar image during natural breathing.

[0029] FIG. 2 is a diagram illustrating an example of a process for calculating a reference position and an area ratio.

[0030] 2 shows a lung region 21 in the planar image during natural breathing, a lung region 22 in the enlarged planar image, and a lung region 23 in the planar image during inspiration. The enlarged planar image is an image obtained by enlarging a lower region 32, located below a predetermined position 31 in the body axis direction Z, in the lung region 21 in the planar image during natural breathing at a predetermined magnification in the body axis direction Z. Therefore, the lower region 33, located below the predetermined position 31 in the enlarged planar image, is larger than the lower region 32 in the planar image during natural breathing.

[0031] Because the lower part of the lungs expands during deep inspiration, lung region 23 in the inhalation planar image is larger than lung region 21 in the natural breathing planar image. For this reason, lung region 22 in the enlarged planar image obtained by enlarging the natural breathing planar image is thought to have a higher degree of agreement (similarity) with the inhalation planar image compared to the natural breathing planar image.

[0032] Therefore, the calculation unit 3 repeatedly executes a calculation process to calculate the image matching degree, which is the degree of matching between the enlarged planar image and the inhalation planar image, while changing the magnification rate of the specified position 31 and the lower region 32, and calculates the specified position 31 and magnification rate when the image matching degree is highest as the reference position and region ratio.

[0033] The image matching degree is not particularly limited as long as it can define the degree of matching between images, and examples thereof include a similarity evaluation function based on the Normalized Mutual Information (NMI) method.

[0034] Returning to the explanation of Figure 1, the enlargement unit 4 generates an enlarged scintigraphy image, which is an enlarged image obtained by enlarging the lung region of the pulmonary perfusion scintigraphy image, based on the area ratio and reference position calculated by the calculation unit 3. Specifically, the enlargement unit 4 identifies the enlargement start position of the pulmonary perfusion scintigraphy image corresponding to the reference position calculated by the calculation unit 3, based on the result of alignment by the alignment unit 2, and generates an enlarged scintigraphy image by enlarging the region below the enlargement start position in the lung region of the pulmonary perfusion scintigraphy image in the body axis direction using the area ratio as the enlargement rate. This enables accurate alignment of the lung region of the enlarged scintigraphy image with the lung region of the chest CT image.

[0035] The fusion unit 5 actually aligns the magnified scintigraphy image generated by the magnification unit 4 with the chest CT image, and generates a fusion image by superimposing the aligned magnified scintigraphy image and the chest CT image. The alignment of the magnified scintigraphy image and the chest CT image can be performed using an existing method for aligning three-dimensional images, such as the Mutual Information (MI) method.

[0036] The output unit 6 outputs the fusion image generated by the fusion unit 5 in a predetermined format. For example, the output unit 6 displays the fusion image on the input / output device 101. Alternatively, instead of displaying the fusion image on the input / output device 101, the output unit 6 may transmit the fusion image to an external device (not shown) via the input / output device 101 or store the fusion image in the auxiliary storage device 102. The predetermined format is not particularly limited, but may be, for example, a DICOM (Digital Imaging and Communications in Medicine) format or a NIfTI (The Neuroimaging Informatics Technology Initiative 1) format.

[0037] FIG. 3 is a flowchart for explaining an example of the overall processing of the image processing device 100.

[0038] First, the acquisition unit 1 acquires, from the auxiliary storage device 102, a chest CT image, a pulmonary perfusion scintigraphy image, an inspiration planar image, and a natural breathing planar image as medical images related to the lungs of the subject (step S101).

[0039] Next, the registration unit 2 generates a two-dimensional image along the coronal plane of the subject as a reference planar image from the pulmonary perfusion scintigraphy image acquired by the acquisition unit 1 (step S102).

[0040] The registration unit 2 aligns the reference planar image with the natural breathing planar image, thereby aligning the reference planar image with the natural breathing planar image and the inhalation planar image (step S103).

[0041] The calculation unit 3 executes a calculation process (see FIG. 4) to calculate an area ratio, which is the ratio of the size of the lung area in the planar image during inhalation to the size of the lung area in the planar image during natural breathing, and a reference position in the body axis direction from which to start calculating the ratio (step S104).

[0042] Based on the result of the alignment by the alignment unit 2, the enlargement unit 4 identifies the position of the pulmonary perfusion scintigraphy image corresponding to the reference position determined by the calculation unit 3 as the enlargement start position, and enlarges the area below the enlargement start position of the pulmonary perfusion scintigraphy image in the body axis direction using the area ratio determined by the calculation unit 3 as the enlargement rate to generate an enlarged scintigraphy image (step S105).

[0043] The fusion unit 5 aligns the enlarged scintigraphy image generated by the enlargement unit 4 with the chest CT image (step S106). The fusion unit 5 generates a fusion image by superimposing the aligned enlarged scintigraphy image and chest CT image (step S107).

[0044] The output unit 6 converts the fusion image generated by the fusion unit 5 into a predetermined format and outputs it (step S108), and the process ends.

[0045] FIG. 4 is a flowchart illustrating an example of the calculation process in step S104 of FIG.

[0046] In the calculation process, the calculation unit 3 first sets a predetermined position in the body axis direction on the natural breathing planar image (step S201). For example, the calculation unit 3 sets each position obtained by dividing the natural breathing planar image at a predetermined interval or a predetermined number of times along the body axis direction as a predetermined position candidate, and sets one of the predetermined position candidates as the predetermined position. Alternatively, the calculation unit 3 may set the position of the top slice of the lung region on the natural breathing planar image as the predetermined position.

[0047] The calculation unit 3 sets a predetermined magnification ratio as the magnification ratio for enlarging the planar image during natural breathing (step S202). For example, the calculation unit 3 sets one of a plurality of predetermined candidates for the predetermined magnification ratio as the initial value of the predetermined magnification ratio. The candidates for the predetermined magnification ratio are, for example, each value obtained by dividing a predetermined range (for example, a range from 1 to 2) into predetermined intervals or predetermined numbers.

[0048] The calculation unit 3 generates an enlarged planar image by enlarging a lower region below a predetermined position in the natural breathing planar image by a predetermined enlargement rate (step S203).

[0049] The calculation unit 3 compares the enlarged planar image with the inspiration planar image, and calculates the image coincidence, which is the degree of coincidence between the enlarged planar image and the inspiration planar image (step S204).

[0050] The calculation unit 3 determines whether or not the termination condition regarding the magnification ratio is satisfied (step S205). For example, when all the candidates for the predetermined magnification ratio have been set, the calculation unit 3 determines that the termination condition regarding the magnification ratio is satisfied.

[0051] If the termination condition regarding the magnification ratio is not satisfied, the calculation unit 3 changes the predetermined magnification ratio (step S206), and the process returns to step S203.

[0052] If the termination condition related to the magnification rate is satisfied, the calculation unit 3 determines whether the termination condition related to the position is satisfied (step S207). For example, the calculation unit 3 determines that the termination condition related to the position is satisfied when all candidates for the predetermined position have been set. Alternatively, the calculation unit 3 may determine that the termination condition is satisfied when the coincidence function reaches a maximum value (local maximum value) using a predetermined optimization method.

[0053] If the termination condition regarding the position is not satisfied, the calculation unit 3 changes the predetermined position (step S208) and returns to the processing of step S202.

[0054] If the termination condition regarding the position is met, the calculation unit 3 identifies the predetermined magnification rate and predetermined position that result in the highest degree of matching from among the calculated image matching degrees as the area ratio and reference position (step S209), and terminates the calculation process.

[0055] As described above, according to this embodiment, the calculation unit 3 calculates an area ratio, which is the ratio between the size of the area corresponding to the subject's organ in the planar image during natural breathing and the size of the area corresponding to the subject's organ in the planar image during inspiration. The enlargement unit 4 generates an enlarged scintigraphy image by enlarging a target area, which is an area corresponding to the subject's organ in the pulmonary perfusion scintigraphy image, based on the area ratio. The fusion unit 5 generates a fusion image by superimposing the enlarged scintigraphy image and the chest CT image. Therefore, the enlarged scintigraphy image, which is an enlarged version of the blood perfusion scintigraphy image according to differences in organ size due to the subject's condition, is superimposed on the chest CT image. This enables accurate superimposition of the chest CT image and the pulmonary perfusion scintigraphy image, thereby enabling more appropriate evaluation of organ function.

[0056] In this embodiment, the organ is the lung, and therefore, it is possible to accurately superimpose images of the lung, which previously was difficult to do because the images change significantly depending on the respiratory state of the subject, and therefore it is possible to more appropriately evaluate lung function.

[0057] Furthermore, in this embodiment, the area ratio in the body axis direction of the subject is calculated, so it is possible to calculate an area ratio that matches the expansion and contraction of the lungs.

[0058] Furthermore, in this embodiment, the area ratio below the reference position in the body axis direction is calculated, so that it is possible to calculate an area ratio that matches the expansion and contraction of the lungs.

[0059] In this embodiment, the calculation unit 3 repeatedly calculates the degree of agreement between an enlarged planar image obtained by enlarging a lower region, which is a region below a reference position in the body axis direction of the lung region in the natural breathing planar image, along the body axis direction, and an inhalation planar image, while changing the enlargement rate of the lower region, and calculates the enlargement rate at which the degree of agreement is highest as the ratio of the target region. This makes it possible to accurately calculate the region ratio.

[0060] In this embodiment, the calculation unit 3 repeatedly executes the calculation process while changing the predetermined position and the magnification ratio of the lower region, and calculates the predetermined position and magnification ratio when the degree of match is highest as the reference position and region ratio, thereby enabling accurate calculation of the region ratio and reference position.

[0061] In this embodiment, the registration unit 2 generates a two-dimensional reference planar image showing the blood flow in the subject's lungs from the lung perfusion scintigraphy image and aligns the reference planar image with the natural breathing planar image. The magnification unit 4 identifies the magnification start position in the lung region of the lung perfusion scintigraphy image based on the registration results by the registration unit 2. This makes it possible to accurately identify the magnification start position in the lung region of the lung perfusion scintigraphy image, thereby enabling more accurate superposition of the chest CT image and the lung perfusion scintigraphy image. [Example]

[0062] In this example, the degree of agreement between magnified scintigraphy images and chest CT images was evaluated.

[0063] Specifically, lung perfusion scintigraphy images and chest CT images were evaluated for 28 subjects suspected of pulmonary thromboembolism who underwent chest CT and lung perfusion SPECT scans, and lung disease was ruled out in the case study. The lung volumes calculated from the chest CT images were used as the reference value, and lung volumes calculated from the lung perfusion scintigraphy images and magnified scintigraphy images were compared. Furthermore, visual evaluation by two nuclear medicine diagnosticians was conducted, and the agreement rates (0-100%) between the lung perfusion scintigraphy images and chest CT images, and between the magnified scintigraphy images and chest CT images (0-100%) were scored on a 5-point scale from 0 to 4. A match rate of 0-25% was scored as "0," a match rate of 25%-50% as "1," a match rate of 50%-75% as "2," a match rate of 75%-90% as "3," and a match rate of over 90% as "4."

[0064] The mean lung volume calculated from chest CT images was 3749 ± 788 ml, and the mean lung volume calculated from lung perfusion scintigraphy images was 3091 ± 610 ml. The P values ​​were less than 0.01, indicating a significant difference between the lung volumes calculated from chest CT images and those calculated from lung perfusion scintigraphy images.

[0065] On the other hand, the mean lung volume calculated from magnified scintigraphy images was 3435±686 ml. The P value for the lung volume calculated from chest CT images and that calculated from magnified scintigraphy images was below the measurement limit, and no significant difference was observed.

[0066] In addition, visual evaluation by two nuclear medicine diagnosticians showed that the average agreement rate between lung perfusion scintigraphy images and chest CT images was 1.9±0.6, and the average agreement rate between magnified scintigraphy images and chest CT images was 3.4±0.7, indicating an improvement.

[0067] Therefore, it has been found that the present disclosure improves the degree of agreement between chest CT images and lung perfusion scintigraphy images (magnified scintigraphy images).

[0068] The above-described embodiments and examples of the present disclosure are merely illustrative examples of the present disclosure, and are not intended to limit the scope of the present disclosure to these embodiments and examples. Those skilled in the art may implement the present disclosure in various other forms without departing from the scope of the present disclosure. [Explanation of symbols]

[0069] 1: Acquisition unit 2: Alignment unit 3: Calculation unit 4: Enlargement unit 5: Fusion unit 6: Output unit 100: Image processing device 101: Input / output device 102: Auxiliary storage device 200: Recording medium

Claims

1. an acquisition unit that acquires a three-dimensional anatomical image that reflects the morphology of an organ of a subject in a first state, a three-dimensional functional image that reflects the function of the organ of the subject in a second state, a two-dimensional first planar image that reflects the function of the organ of the subject in the first state, and a two-dimensional second planar image that reflects the function of the organ of the subject in the second state; a calculation unit that calculates a ratio of a size of a region corresponding to the organ in the first planar image to a size of a region corresponding to the organ in the second planar image; an enlargement unit that generates an enlarged image by enlarging a target region in the functional image that corresponds to the organ based on the ratio; a fusion unit that generates a fusion image by superimposing the enlarged image and the morphological image.

2. the organ is a lung; The program of claim 1 , wherein the functional image, the first planar image, and the second planar image show blood flow in the lungs.

3. The program according to claim 2 , wherein the calculation unit calculates the ratio in a body axis direction of the subject.

4. the calculation unit calculates the ratio below a predetermined reference position in the body axis direction, The program according to claim 3 , wherein the enlargement unit enlarges a region below an enlargement start position corresponding to the reference position in the target region.

5. 5. The program according to claim 4, wherein the calculation unit repeatedly executes a calculation process to calculate a degree of correspondence between the first planar image and an enlarged planar image obtained by enlarging a lower region of the target region of the second planar image, which is an area below a predetermined position in the body axis direction, at a predetermined magnification rate along the body axis direction, while changing the magnification rate, and calculates the magnification rate when the degree of correspondence is highest as the ratio.

6. The program according to claim 5 , wherein the calculation unit repeatedly executes the calculation process while changing the position and the magnification ratio, and calculates the position and the magnification ratio when the degree of match is highest as the reference position and the ratio.

7. a registration unit that generates a two-dimensional third planar image showing blood flow in the lungs of the subject from the functional image and registers the third planar image with the first planar image and the second planar image; The program according to claim 4 , wherein the enlargement unit specifies the enlargement start position based on a result of alignment performed by the alignment unit.

8. an acquisition unit that acquires a three-dimensional anatomical image that reflects the morphology of an organ of a subject in a first state, a three-dimensional functional image that reflects the function of the organ of the subject in a second state, a two-dimensional first planar image that reflects the function of the organ of the subject in the first state, and a two-dimensional second planar image that reflects the function of the organ of the subject in the second state; a calculation unit that calculates a ratio of a size of a region corresponding to the organ in the first planar image to a size of a region corresponding to the organ in the second planar image; an enlargement unit that generates an enlarged image by enlarging a target region in the functional image that corresponds to the organ based on the ratio; a fusion unit that generates a fusion image by superimposing the enlarged image and the morphological image.

9. acquiring a three-dimensional anatomical image reflecting the morphology of an organ of the subject in a first state, a three-dimensional functional image reflecting the function of the organ of the subject in a second state, a first two-dimensional planar image reflecting the function of the organ of the subject in the first state, and a second two-dimensional planar image reflecting the function of the organ of the subject in the second state; calculating a ratio of a size of a region corresponding to the organ in the first planar image to a size of a region corresponding to the organ in the second planar image; an enlargement unit that generates an enlarged image by enlarging a target region in the functional image that corresponds to the organ based on the ratio; an image processing method for generating a fusion image by superimposing the enlarged image and the morphological image;

Images