JP2014215238A - Nuclear medicine image reconstruction apparatus, nuclear medicine image reconstruction method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a SPECT image reconstruction apparatus capable of properly performing an attenuation correction using a X ray CT image.SOLUTION: The SPECT image reconstruction apparatus obtains a SPECT imaging image and a X ray CT image from a patient (P1). When a CT value of the X ray CT image is converted into a linear attenuation coefficient so as to generate an attenuation coefficient map, its conversion ratio is changed to generate a plurality of attenuation coefficient maps (P2), and the imaged image is subjected to attenuation correction using a plurality of generated attenuation coefficient maps (P3), and a plurality of attenuation correction images is reconstructed (P4). Next, the plurality of attenuation correct images (P4) and control data (P5) are compared on a polar map (P6), and the attenuation correction image of the patient whose alienating part size becomes the maximum is obtained and outputted as an optimum attenuation correction image (P7).

Description

  The present invention relates to a technique for reconstructing a positron emission tomography (hereinafter referred to as “PET”) image and a single photon emission tomography (hereinafter referred to as “SPECT”) image.

  Nuclear medicine images represented by PET images and SPECT images are effective in diagnosing various diseases including heart diseases and cancers. These images are administered with a drug labeled with a specific radioisotope (hereinafter referred to as “radiopharmaceutical”), and γ rays emitted directly or indirectly from the drug are detected by a dedicated camera. Obtained by rebuilding. Nuclear medicine images not only have excellent properties such as high specificity and sensitivity to diseases, but also have characteristics not found in other diagnostic images that can provide information on the function of lesions. Yes.

  Nuclear medicine images are obtained by detecting gamma rays emitted directly or indirectly from a radiopharmaceutical administered to a subject. Since γ-rays are attenuated in the living body, the count of detected γ-rays is attenuated according to the depth from the body surface. Therefore, in order to accurately reconstruct a nuclear medicine image using the detected γ-ray count, it is necessary to perform attenuation correction in consideration of attenuation of γ-rays in the living body.

  For attenuation correction, it is preferable to use an attenuation coefficient map. Up to now, various methods for creating attenuation coefficient maps have been devised and used for attenuation correction (Non-Patent Document 1). One conventional attenuation correction method uses an X-ray CT image. This method is evaluated to be the most effective method not only because it can collect attenuation correction data with no noise in a short time but also obtain a morphological image at the same time.

Seiichi Shunichi April, “Fundamentals and usefulness of attenuation correction method in PET and PET / CT” Journal of Japanese Society of Radiological Technology, Vol. 62, No. 6, pages 797-803

  As described above, it is known that it is necessary to perform attenuation correction in consideration of attenuation of γ rays in the case of SPECT and attenuation of annihilation radiation (photons) in the case of PET, and attenuation correction has been performed. The attenuation correction method generally creates an attenuation correction map by converting the CT value of each pixel of an X-ray CT image into a theoretical value of a linear attenuation coefficient. However, in practice, the attenuation coefficient map created according to the theoretical value is not always appropriate. In some cases, if the attenuation coefficient map generated from the X-ray CT image is used as it is, the correction is excessively performed. Sometimes it was done.

  In view of the above background, an object of the present invention is to provide a nuclear medicine image reconstruction apparatus capable of appropriately performing attenuation correction using an X-ray CT image.

  A nuclear medicine image reconstruction apparatus according to the present invention includes a captured image of a patient captured by PET or SPECT, an captured image acquisition unit that acquires an X-ray CT image of the patient, and a CT value of the X-ray CT image as a line. An attenuation coefficient map generation unit that generates an attenuation coefficient map by converting into an attenuation coefficient, and uses the attenuation coefficient map generation unit that generates a plurality of attenuation coefficient maps by changing the conversion rate, and the plurality of attenuation coefficient maps. An attenuation correction image generation unit that generates a plurality of attenuation correction images by performing attenuation correction on the captured image, and an attenuation correction image generated by a plurality of attenuation correction maps for a healthy person were used to generate each attenuation correction image. A control database stored in association with the conversion rate of the attenuation coefficient map, and a conversion used for generating a plurality of attenuation correction images of the patient from the control database Read a plurality of attenuation correction images of a healthy person with the same conversion rate, compare the attenuation correction image of the patient with the same conversion rate and the attenuation correction image of the healthy person, and the difference between the pixel values is larger than a predetermined threshold An optimal attenuation correction image determination unit that obtains an attenuation correction image of a patient whose size is the maximum as an optimal attenuation correction image, and an image output unit that outputs the optimal attenuation correction image. Here, since the divergence portion is a portion having a large difference in the number of pixels, for example, in the case of cerebral blood flow SPECT or myocardial blood flow SPECT, it is a defective portion, and in the case of PET, it is a positive detection portion.

  According to the present invention, a nuclear medicine image with appropriate attenuation correction can be obtained by generating an attenuation correction image in which the size of the divergence portion is maximum as compared with a captured image of a healthy person.

It is a figure which shows the outline | summary of the SPECT image reconstruction apparatus of 1st Embodiment. It is a figure which shows the structure of the SPECT image reconstruction apparatus of 1st Embodiment. It is a figure which shows an example among the methods of converting CT value into a linear attenuation coefficient. It is a figure which shows the hardware of the SPECT image reconstruction apparatus of 1st Embodiment. It is a figure which shows operation | movement of the SPECT image reconstruction apparatus of 1st Embodiment. It is a figure which shows the operation | movement which determines the optimal attenuation | damping correction image by the SPECT image reconstruction apparatus of 1st Embodiment. It is a figure which shows the operation | movement which reconstructs the optimal attenuation | damping correction image by the SPECT image reconstruction apparatus of 2nd Embodiment. It is a figure which shows the ROC curve which detects the case of coronary artery stenosis by the attenuation correction image calculated | required by this invention compared with the case where the image which does not perform attenuation correction, and the case where the attenuation correction image by a theoretical value (conventional) is used.

  Hereinafter, a nuclear medicine image reconstruction apparatus according to an embodiment of the present invention will be described with reference to the drawings. In the following description, an example of reconstructing a loaded myocardial SPECT image will be described.

(First embodiment)
FIG. 1 is a diagram for explaining an outline of processing by the SPECT image reconstruction apparatus according to the embodiment. The SPECT image reconstruction apparatus is connected to a SPECT-CT apparatus in which a gamma camera and a multi-slice CT are integrated. The SPECT image reconstruction apparatus acquires a SPECT captured image and an X-ray CT image of the patient from the SPECT-CT apparatus (P1). In FIG. 1, “(original)” is described in the sense of a SPECT image before appropriate attenuation correction is performed.

  First, the SPECT image reconstruction device generates an attenuation coefficient map using an X-ray CT image. In the present embodiment, in addition to a known attenuation coefficient map composed of theoretical values of linear attenuation coefficients, a plurality of attenuation coefficient maps are generated by changing the conversion rate from CT values to linear attenuation coefficients (P2). Here, an arbitrary numerical value of 0 to 100% can be used for the conversion rate. 0% is no attenuation correction, and 100% is an attenuation correction based on a theoretical value. In FIG. 1, for convenience of explanation, cases where 100%, 80%, 60%, and 40% are used as arbitrary conversion rates are described as examples, but the conversion rates are of course not limited to these values. Absent. Note that as the conversion rate to the linear attenuation coefficient decreases, the attenuation correction ratio decreases.

  Next, the SPECT image reconstruction device uses the plurality of attenuation coefficient maps generated at an arbitrary conversion rate to attenuate and correct the SPECT image of the patient (P3), and regenerates the corresponding attenuation correction image (P4). Configure.

  Next, the SPECT image reconstruction device uses an attenuation correction image (P4) of the reconstructed patient and an attenuation coefficient map created at the same conversion rate (this attenuation coefficient map is an attenuation coefficient map of a healthy person). Then, the attenuation correction image (P5) of the healthy person who has been corrected is compared (P6). In the example shown in FIG. 1, four attenuation correction images generated using attenuation coefficient maps created at conversion rates of 100%, 80%, 60%, and 40% are compared. In this comparison, both the attenuation correction image of the patient and the attenuation correction image of the healthy person are displayed on the polar map, and the pixel values of the corresponding pixels are compared. If there is a difference in the pixel value between the patient attenuation correction image and the attenuation correction image of the healthy subject that is greater than or equal to a predetermined threshold value, it is determined that it is a divergence part (ischemic disease part). In the attenuation correction image of each conversion rate, the size of the divergence portion (number of pixels of the divergence portion) is obtained, and it is determined that the attenuation correction image having the maximum size of the divergence portion is the optimum attenuation correction image. In the example shown in FIG. 1, it is determined that the attenuation-corrected image that has been attenuation-corrected with the 80% attenuation coefficient map is optimal. The SPECT image reconstruction apparatus outputs the attenuation correction image thus obtained (in the example shown in FIG. 1, the attenuation correction image based on the 80% attenuation coefficient map) as a SPECT image (P7) subjected to attenuation correction. .

  FIG. 2 is a diagram illustrating a configuration of the SPECT image reconstruction device 10 according to the present embodiment. As described above, the nuclear medicine image is connected to the SPECT-CT apparatus 17. The SPECT image reconstruction apparatus 10 includes a captured image acquisition unit 11 that acquires a SPECT image and an X-ray CT image from the SPECT-CT apparatus 17. The SPECT image reconstruction device 10 acquires a captured image of the loaded myocardial SPECT from the SPECT-CT device 17. In the present embodiment, the captured image acquisition unit 11 is described as an example of acquiring a captured image directly from the SPECT-CT apparatus 17. However, the captured image acquisition unit 11 is configured to acquire a SPECT captured image and an X-ray CT. It is good also as acquiring a captured image from the storage medium which memorize | stored the image.

  The SPECT image reconstruction apparatus 10 reconstructs an attenuation coefficient map generation unit 12 that generates a plurality of attenuation coefficient maps based on an X-ray CT image, and an attenuation correction image obtained by performing attenuation correction on a patient's SPECT captured image in a plurality of ways. An attenuation-corrected image reconstruction unit 13 and an optimum attenuation-corrected image determination unit 14 for obtaining an optimum attenuation-corrected image among a plurality of attenuation-corrected images.

  The attenuation correction map generation unit calculates a line attenuation coefficient for each pixel based on a CT value (unit: Hounsfield Unit) obtained from the X-ray CT image, and generates an attenuation coefficient map. The attenuation correction map generated here is considered to be theoretically optimal as the attenuation coefficient map generated from the X-ray CT image. Conventionally, the attenuation coefficient map generated in this way is used as the attenuation coefficient map. Attenuation correction was performed as it was. The attenuation coefficient map generation unit 12 according to the present embodiment converts an arbitrary conversion of 0 to 100% when a theoretical conversion when converting a CT value into a linear attenuation coefficient is a 100% attenuation coefficient map. A plurality of attenuation correction maps converted into linear attenuation coefficients at a rate are generated.

In general, the relationship between the CT value and the linear attenuation coefficient is expressed by two linear functions with the CT value “0HU” as a boundary. By changing the slopes of these two linear functions, there are innumerable values in theory. An attenuation correction map is obtained. FIG. 3 is a diagram illustrating an example of converting a CT value for generating an attenuation correction map into a linear attenuation coefficient using conversion rates of 100%, 80%, 60%, and 40% as an example. As shown in FIG. 3, the slope of the linear function from −1000 HU (air) to 0 HU (water) and the slope of the linear function from 0 HU (water) to 1000 HU (bone) are changed. For example, when an attenuation coefficient map is generated with a conversion rate of 80%, x is a CT value, y is a linear attenuation coefficient, and y = 11.1 × 10 ⁻⁵ x + 0.123 when the CT value is 0 or less. In the range where the CT value is greater than 0, conversion is performed at a conversion rate of y = 7.08 × 10 ⁻⁵ x + 0.119. It should be noted that different conversion rates may be employed in the region where the CT value is 0 HU or less and the region where the CT value is greater than 0 HU, and this makes it possible to create an attenuation coefficient map suitable for the purpose of use. Again, FIG. 3 is an example showing a conversion method at an arbitrary conversion rate, and the conversion rates of a plurality of attenuation correction images generated by the SPECT image reconstruction device 10 of the present embodiment are limited to these. It is not something.

  The attenuation correction image reconstruction unit 13 has a function of reconstructing a plurality of attenuation correction images by performing attenuation correction of the SPECT captured image of the patient using a plurality of attenuation coefficient maps.

  The optimum attenuation correction image determination unit 14 has a function of determining which attenuation correction image is optimum among the plurality of attenuation correction images. In the loaded myocardial SPECT, since the ischemic part is depicted as a cold spot, the divergence part is confirmed as a defect part. Since the image with the largest missing part is considered to reflect the actual situation most, the attenuation corrected image with the largest missing part is the optimum attenuation corrected image. The optimal attenuation correction image determination unit 14 is connected to a control database 15 (denoted as “CDB” in FIG. 2) that stores a load myocardial SPECT image of a healthy person. The control database 15 stores a plurality of attenuation correction images obtained by attenuation-correcting a load myocardial SPECT image of a healthy person with a plurality of attenuation coefficient maps having different conversion rates. The control database 15 stores data of a plurality of healthy persons, and the attenuation correction image is converted into a polar map. That is, the control database 15 stores data such as the average value and standard deviation of each pixel on the polar map of the load myocardium SPECT of a healthy person.

  The optimum attenuation correction image determination unit 14 reads out the attenuation correction image subjected to the attenuation correction using the attenuation coefficient map having the same conversion rate as that of the patient from the control database 15 storing the loaded myocardial SPECT image of the healthy person. Then, the optimum attenuation correction image determination unit 14 compares the attenuation correction image of the patient and the attenuation correction image of the healthy person for each pixel on the polar map, and counts the number of pixels whose pixel value difference is equal to or greater than a predetermined threshold value. To do. In the present embodiment, for example, (average −2SD (Standard Deviation)) of blood flow (pixel value) of a healthy person is used as the predetermined threshold. That is, pixels that are lower than (average −2SD) of blood flow (pixel value) of healthy persons are counted as divergence parts. Of course, it goes without saying that the threshold value is not limited to (average-2SD), and can be appropriately changed according to the case, the purpose of diagnosis, and the like. For example, in the case of PET in which the divergence part is detected as a positive detection part, (average + 2SD). The optimum attenuation correction image determination unit 14 performs this comparison process for each attenuation correction image having the same conversion rate, and determines that the attenuation correction image having the largest deviation portion is the optimum attenuation correction image.

  The output unit 16 outputs the optimal attenuation correction image determined by the optimal attenuation correction image determination unit 14. As an output method, for example, it may be displayed on a screen or transmitted to another device.

  FIG. 4 is a diagram illustrating a hardware configuration of the SPECT image reconstruction apparatus 101 described above. The SPECT image apparatus 1 includes a computer in which a CPU 20, a RAM 21, a ROM 22, a keyboard 24, a mouse 25, a display 26, a speaker 27, a hard disk 28, and a communication unit 29 are connected by a data bus 30. The communication unit 29 is connected to the SPECT-CT apparatus 17 and captures a SPECT captured image or an X-ray CT image. The function of the SPECT image reconstruction apparatus 10 described above is realized by the CPU 20 executing arithmetic processing according to the program 23 written in the ROM 22. Such a program 23 is included in the scope of the present invention.

  FIG. 5 is a diagram illustrating the operation of the SPECT image reconstruction apparatus 10 according to the present embodiment. The SPECT image reconstruction apparatus 10 first acquires a patient's loaded myocardial SPECT image and X-ray CT image from the SPECT-CT apparatus 17 (S10). Next, the SPECT image reconstruction apparatus 10 generates an attenuation coefficient map by converting the CT value of each pixel of the X-ray CT image into a corresponding line attenuation coefficient (S11). As described above, the SPECT image reconstruction device 10 generates a plurality of attenuation coefficient maps by changing the conversion rate from the CT value to the linear attenuation coefficient.

  Subsequently, the SPECT image reconstruction device 10 attenuates and corrects the SPECT captured image of the patient using a plurality of attenuation coefficient maps, and reconstructs a plurality of attenuation correction images (S12). The SPECT image reconstruction apparatus 10 determines an optimum attenuation correction image from among a plurality of attenuation correction images of the patient by comparing with the attenuation correction image of the healthy person stored in the control database 15 (S13). This process will be described later with reference to FIG. When the SPECT image reconstruction device 10 determines the optimum attenuation correction image, the SPECT image reconstruction device 10 outputs the attenuation correction image by displaying it on the display (S14).

  FIG. 6 is a diagram illustrating an operation for determining an optimal attenuation correction image. The SPECT image reconstruction device 10 converts the attenuation correction image of the patient into a polar map and standardizes it so that the attenuation correction image stored in the control database 15 can be compared (S20).

  Next, the SPECT image reconstruction device 10 selects one of a plurality of attenuation correction images of the patient, reads out an attenuation correction image of a healthy person having the same conversion rate as that attenuation correction image (S21), and attenuates the patient. The corrected image and the attenuation correction image of the healthy person are compared for each pixel, and the number of abnormal pixels is counted (S22). Next, it is determined whether or not all attenuation correction images have been compared with the attenuation correction image of the healthy person (S23), and if it is determined that the comparison for all attenuation correction images has not been completed. (NO in S23), another attenuation correction image is selected from a plurality of attenuation correction images of the patient, and the same comparison as described above is performed for the attenuation correction image (S21, S22).

  When the comparison with the control data is completed for all attenuation correction images of the patient (YES in S23), and the count of abnormal pixels for each attenuation correction image is completed, the SPECT image reconstruction device 10 includes a plurality of SPECT image reconstruction devices 10. The attenuation correction image having the maximum number of abnormal pixels is determined as the optimum attenuation correction image (S24).

  The configuration and operation of the SPECT image reconstruction apparatus 10 according to the present embodiment have been described above. The SPECT image reconstruction apparatus 10 according to the present embodiment attenuates not only by a theoretical attenuation coefficient map obtained from an X-ray CT image but also by a plurality of attenuation coefficient maps in which conversion rates from CT values to linear attenuation coefficients are changed. Since the correction image is reconstructed and the optimum attenuation correction image is reconstructed compared with the control database 15, it is possible to solve the problem such as overcorrection by the attenuation coefficient map and obtain a SPECT image well representing the actual situation. it can.

(Second Embodiment)
Next, a SPECT image reconstruction apparatus according to the second embodiment of the present invention will be described. The basic configuration of the SPECT image reconstruction apparatus of the second embodiment is the same as that of the first embodiment, but the SPECT image reconstruction apparatus of the second embodiment is a polar map of the heart. The difference is that an optimal attenuation correction image is reconstructed for each segment.

  The polar map of the heart is divided into 17 segments. The SPECT image reconstruction apparatus 10 according to the second embodiment compares the control data for each segment, counts the number of abnormal pixels, and reconstructs an optimal attenuation correction image.

  FIG. 7 is a diagram illustrating an operation for reconstructing an optimal attenuation correction image in the second embodiment. The SPECT image reconstruction apparatus 10 converts the patient attenuation correction image into a polar map and standardizes it so that the attenuation correction image stored in the control database 15 can be compared (S30).

  Next, the SPECT image reconstruction device 10 selects one of a plurality of attenuation correction images of the patient, reads out an attenuation correction image of a healthy person having the same conversion rate as that attenuation correction image (S31), and for each segment. Then, the attenuation correction image of the patient and the attenuation correction image of the healthy person are compared for each pixel, and the number of abnormal pixels is counted (S32). Next, it is determined whether or not all attenuation correction images have been compared with the attenuation correction image of the healthy person (S33). If it is determined that the comparison of all attenuation correction images has not been completed. (NO in S33), another attenuation correction image is selected from the plurality of attenuation correction images of the patient, and the same comparison as above is performed for the attenuation correction image (S31, S32).

  When the comparison with the control data is completed for all attenuation correction images of the patient (YES in S33), and the count of abnormal pixels for each attenuation correction image is completed, the SPECT image reconstruction device 10 includes a plurality of SPECT image reconstruction apparatuses 10. The attenuation-corrected image having the maximum number of abnormal pixels is determined for each segment among the attenuation-corrected images (S34). Subsequently, the SPECT image reconstruction device 10 combines the optimum attenuation correction images determined for each segment to synthesize the optimum attenuation correction image (S35).

  The present inventors have found that the segment affected by the CT attenuation correction is changed by changing the level of the CT attenuation correction stepwise. Based on this knowledge, by combining optimal attenuation correction images for each segment, SPECT images in which optimal attenuation correction has been performed for all segments can be obtained.

  In this embodiment, an example in which optimal attenuation correction images obtained for each segment of the polar map of the heart are combined has been described. However, the method of dividing the imaging target is not limited to the polar map segment. Alternatively, it may be every part where the imaging object is classified functionally or morphologically. For example, in the case of a cerebral blood flow image, an optimum attenuation correction image may be obtained for each atlas segment and combined.

  FIG. 8 shows attenuation correction images (MaxS TPD goup) obtained by the present invention and images without attenuation correction for 156 cases (98 coronary artery disease groups, 58 non-coronary artery disease groups) subjected to coronary angiography. (CT-AC 0% group) and the attenuation correction image by the theoretical value (CT-AC 100% group), the coronary artery stenosis degree> 50% by QCA (Quantitative Coronary Analysis) by coronary angiography An ROC (Receiver Operating Characteristic) curve was created assuming that the recognized cases were ill and the cases with coronary stenosis <50% were ill. When the optimal attenuation correction image (MaxS TPD goup) was used, the AUC (Area Under Curve) was the highest, and other groups were included. That is, the diagnostic ability is high. In addition, when the κ statistics between each group were calculated, MaxS TPD goup vs. CT-AC 0% group and MaxS TPD goup vs. CT-AC 100% group were both κ statistics <0.4. It became clear that it can be judged as a different examination type.

  The nuclear medicine image reconstruction apparatus of the present invention has been described in detail with reference to the embodiment, but the present invention is not limited to the above-described embodiment.

  In the above-described embodiment, the load myocardial SPECT image has been described as an example. However, the attenuation correction by the nuclear medicine image reconstruction device of the present invention is not limited to the SPECT image, but also applied to the PET image. Can do. In addition, the present invention is not limited to an image of a load myocardium, and can be applied to a cerebral blood flow image or the like.

  In the above-described embodiment, an example in which a theoretical attenuation coefficient map is set to 100% and an attenuation coefficient map having a smaller conversion rate is used has been described. However, the present invention has a theoretical value such as 110% or 120%. An attenuation coefficient map having a conversion rate larger than a typical attenuation coefficient map may be used. In particular, in the case of PET in which the divergence part is detected as a positive detection part, even a value larger than 100% may be applicable.

  As described above, according to the present invention, a nuclear medicine image in which appropriate attenuation correction is performed by reconstructing an attenuation correction image in which the size of the divergence portion is maximum as compared with a captured image of a healthy person. It is useful as a device that reconstructs an image with high diagnostic ability by appropriately processing an image captured by SPECT or PET.

DESCRIPTION OF SYMBOLS 10 SPECT image reconstruction apparatus 11 Captured image acquisition part 12 Attenuation coefficient map generation part 13 Attenuation correction image reconstruction part 14 Optimal attenuation correction image determination part 15 Control database 16 Output part 17 SPECT-CT apparatus 20 CPU
21 RAM
22 ROM
23 Program 24 Keyboard 25 Mouse 26 Display 27 Speaker 28 Hard Disk 29 Communication Unit 30 Data Bus

Claims (12)

A captured image of a patient imaged by PET or SPECT, and a captured image acquisition unit for acquiring an X-ray CT image of the patient;
An attenuation coefficient map generation unit that converts a CT value of the X-ray CT image into a linear attenuation coefficient to generate an attenuation coefficient map, and generates an attenuation coefficient map by changing the conversion rate. When,
An attenuation-corrected image reconstruction unit for reconstructing a plurality of attenuation-corrected images by performing attenuation correction on the captured image using the plurality of attenuation coefficient maps;
A control database that stores attenuation correction images reconstructed by a plurality of attenuation correction maps for healthy individuals in association with conversion rates of attenuation coefficient maps used for the reconstruction of the respective attenuation correction images;
From the control database, read a plurality of attenuation correction images of a healthy person having the same conversion rate as the conversion rate used for reconstructing the plurality of attenuation correction images of the patient, and the attenuation correction image of the patient and the normality having the same conversion rate An optimal attenuation correction image determination unit that compares the attenuation correction image of the patient and obtains the attenuation correction image of the patient whose difference in pixel value is larger than a predetermined threshold value as the maximum attenuation correction image of the patient,
An image output unit for outputting the optimum attenuation correction image;
A nuclear medicine image reconstruction apparatus comprising:   The captured image of the patient is a loaded myocardial SPECT image captured for the patient, and the attenuation correction image reconstructed by a plurality of attenuation correction maps for the healthy person is obtained by using the loaded myocardial SPECT image captured for the healthy person. The nuclear medicine image reconstruction apparatus according to claim 1, which is a created attenuation correction image.   The kernel according to claim 1 or 2, wherein a slope of a linear function representing a conversion rate for generating the attenuation correction map is changed and set in an area where the HU value of the X-ray CT image is larger than 0 and small. Medical image reconstruction device.   The nuclear medicine image reconstruction apparatus according to any one of claims 1 to 3, wherein the optimum attenuation correction image is obtained for each part where the imaging target is classified functionally or morphologically. Acquiring a captured image of a patient imaged by PET or SPECT, and an X-ray CT image of the patient;
Converting the CT value of the X-ray CT image into a linear attenuation coefficient to generate an attenuation coefficient map, and changing the conversion rate to generate a plurality of attenuation coefficient maps;
Reconstructing a plurality of attenuation corrected images by performing attenuation correction on the captured image using the plurality of attenuation coefficient maps;
A plurality of attenuation corrections of the patient from a control database in which attenuation correction images reconstructed by a plurality of attenuation correction maps for healthy subjects are stored in association with conversion rates of attenuation coefficient maps used for the reconstruction of the respective attenuation correction images. Read a plurality of attenuation correction images of a healthy person with the same conversion rate as the conversion rate used for image reconstruction, compare the attenuation correction image of the patient with the same conversion rate and the attenuation correction image of the healthy person, pixel value A step of obtaining an attenuation correction image of a patient having a maximum difference between the difference of greater than a predetermined threshold as an optimal attenuation correction image;
Outputting the optimal attenuation correction image;
A nuclear medicine image reconstruction method comprising:   The captured image of the patient is a loaded myocardial SPECT image captured for the patient, and the attenuation correction image reconstructed by a plurality of attenuation correction maps for the healthy person is obtained by using the loaded myocardial SPECT image captured for the healthy person. The nuclear medicine image reconstruction method according to claim 5, wherein the nuclear medicine image reconstruction method is a created attenuation correction image.   The kernel according to claim 5 or 6, wherein an inclination of a linear function representing a conversion rate for generating the attenuation correction map is set by changing between a region where the HU value of the X-ray CT image is larger than 0 and a region where the HU value is small. Medical image reconstruction method.   The nuclear medicine image reconstruction method according to any one of claims 5 to 7, wherein the optimum attenuation correction image is obtained for each part where the imaging target is classified functionally or morphologically. A program for reconstructing a nuclear medicine image by performing attenuation correction on a captured image of a patient imaged by PET or SPECT,
Obtaining a captured image of the patient and an X-ray CT image of the patient;
Converting the CT value of the X-ray CT image into a linear attenuation coefficient to generate an attenuation coefficient map, and changing the conversion rate to generate a plurality of attenuation coefficient maps;
Reconstructing a plurality of attenuation corrected images by performing attenuation correction on the captured image using the plurality of attenuation coefficient maps;
A plurality of attenuation corrections of the patient from a control database in which attenuation correction images reconstructed by a plurality of attenuation correction maps for healthy subjects are stored in association with conversion rates of attenuation coefficient maps used for the reconstruction of the respective attenuation correction images. Read a plurality of attenuation correction images of a healthy person with the same conversion rate as the conversion rate used for image reconstruction, compare the attenuation correction image of the patient with the same conversion rate and the attenuation correction image of the healthy person, pixel value A step of obtaining an attenuation correction image of a patient having a maximum difference between the difference of greater than a predetermined threshold as an optimal attenuation correction image;
Outputting the optimal attenuation correction image;
A program that executes   The captured image of the patient is a loaded myocardial SPECT image captured for the patient, and the attenuation correction image reconstructed by a plurality of attenuation correction maps for the healthy person is obtained by using the loaded myocardial SPECT image captured for the healthy person. The program according to claim 9, which is a created attenuation correction image.   The program according to claim 9 or 10, wherein a slope of a linear function representing a conversion rate for generating the attenuation correction map is changed and set in an area where the HU value of an X-ray CT image is larger than 0 and small. .   The program according to any one of claims 9 to 11, wherein the optimum attenuation correction image is obtained for each part where the imaging target is classified functionally or morphologically.