JP6951169B2 - Nuclear medicine diagnostic equipment - Google Patents

Description

Embodiments of the present invention relate to nuclear medicine diagnostic equipment.

In nuclear medicine diagnostic equipment such as SPECT (Single Photon Emission computed Tomography) equipment, chemicals (blood flow markers, tracers) containing radioisotopes (hereinafter referred to as RI) selectively apply to specific tissues and organs in the living body. Utilizing the property of being taken in, gamma rays emitted from RI distributed in the living body are detected by a gamma camera having a gamma ray detector arranged outside the living body. The nuclear medicine diagnostic apparatus can provide a functional image of an internal organ or the like by generating a nuclear medicine image that images the dose distribution of gamma rays detected by a gamma ray detector.

Gamma rays emitted from RI are attenuated in tissues within the body of the subject. Therefore, in order to take this attenuation into consideration, the nuclear medicine diagnostic apparatus generally performs correction (attenuation correction) based on the attenuation coefficient distribution (attenuation distribution) when generating a nuclear medicine image. In order to obtain an accurate attenuation distribution, it is preferable to estimate the body contour of the subject in the nuclear medicine image as accurately as possible.

As a method for estimating the body contour of a subject, there are a method using an X-ray CT (Computed Tomography) image and a method using a nuclear medicine image. However, the method using the X-ray CT image requires an X-ray CT image of the subject in addition to the nuclear medicine image, and it is difficult to accurately align the X-ray CT image with the nuclear medicine image. There is a problem such as increased exposure.

On the other hand, in the method of estimating the body contour of the subject in the nuclear medicine image using the nuclear medicine image, it is not necessary to use the X-ray CT image. For example, there is an SSPAC method (Segmentation with Scatter and Photopeak window Data for Attenuation Correction) as a method of extracting a body contour from a nuclear medicine reconstructed image and creating an attenuation distribution of the body part. According to this kind of method, an attenuated distribution of the body can be created from a nuclear medicine reconstructed image without using an X-ray CT image.

In general, in the body contour extraction process applied to the nuclear medicine reconstructed image, including the body contour extraction process performed in the SSPAC method, a method of setting a threshold value for the count value is often used. Further, as the body contour extraction process, a filter process for contour extraction such as an edge enhancement process or a differential filter may be used.

However, in these body contour extraction processes applied to the nuclear medicine reconstructed image, the influence of the high count part in the nuclear medicine reconstructed image, the problem of insufficient count value, and the problem of attenuation due to the top plate located in the image. Therefore, it is difficult to extract an accurate body contour from a nuclear medicine reconstructed image.

Japanese Unexamined Patent Publication No. 2007-248121

An object to be solved by the present invention is to provide a nuclear medicine diagnostic apparatus capable of performing preprocessing for correcting nuclear medicine reconstruction data into reconstruction data suitable for body contour extraction processing.

In order to solve the above-mentioned problem, the nuclear medicine diagnostic apparatus according to the embodiment of the present invention corrects the reconstruction data based on gamma rays so as to be the reconstruction data suitable for the contour extraction process for extracting the body contour. An area of interest acquisition unit for acquiring a region of interest corresponding to the body contour of the subject, which is set for reconstruction data based on gamma rays emitted from the subject, and the subject. A storage unit that stores a top plate attenuation correction map for correcting the attenuation of gamma rays by the top plate on which the sample is placed, an alignment unit that aligns the region of interest with the top plate attenuation correction map, and an alignment unit. Based on the mask data generation unit that generates mask data having a higher weight than the reconstruction data on the center side with respect to the reconstruction data on the edge side in the region of interest, the top plate attenuation correction map, and the mask data. It is provided with a correction reconstruction data generation unit that generates correction reconstruction data by correcting the reconstruction data.

The block diagram which shows an example of the nuclear medicine diagnostic apparatus 1 which concerns on one Embodiment of this invention. A schematic block diagram showing an example of a function realized by a processor of a processing circuit. The figure for demonstrating the outline of the pretreatment which concerns on this embodiment. The flowchart which shows an example of the procedure when the preprocessing is executed by the processor of the processing circuit shown in FIG. The explanatory view which shows an example of how the region of interest 51 is set when the scattered ray reconstruction image of the same slice and the main reconstruction image are displayed in parallel. The explanatory view which shows an example of the setting method of the sub-window corresponding to a scattered ray reconstructed image, and the main window corresponding to a main reconstructed image. FIG. 6 is a subroutine flowchart showing an example of the procedure of the top plate attenuation correction processing executed in step S3 of FIG. (A) is an explanatory diagram showing an example of the original data including the estimated area of the top plate, (b) is an explanatory diagram showing an example of the attenuation distribution map of the top plate, and (c) is an example of the top plate attenuation correction map. Explanatory drawing which shows. Explanatory drawing which shows an example of the state of alignment of interest area and top plate attenuation correction map. FIG. 6 is a subroutine flowchart showing an example of a procedure of mask data correction processing executed in step S4 of FIG. (A) is an explanatory diagram showing a first example of mask data, (b) is an explanatory diagram showing a second example of mask data, and (c) is an explanatory diagram showing a third example of mask data. Explanatory drawing which shows an example of the mask data 71 which was set to approach zero according to the distance from the boundary of an area of interest. (A) is an explanatory diagram showing an example of the body contour extracted using the reconstruction data not subjected to the pretreatment according to the present embodiment, and (b) is the corrected reconstruction with the pretreatment according to the present embodiment. Explanatory drawing which shows an example of the body contour extracted using data.

An embodiment of the nuclear medicine diagnostic apparatus according to the present invention will be described with reference to the accompanying drawings. In the following description, an example in which a two-detector type gamma ray detector rotation type SPECT device is used as the nuclear medicine diagnostic device according to the present invention will be described. The gamma ray detector rotating SPECT apparatus may have one or three or more gamma ray detectors.

(overall structure)
FIG. 1 is a block diagram showing an example of a nuclear medicine diagnostic apparatus 1 according to an embodiment of the present invention. The nuclear medicine diagnostic device 1 has a scanner device 2 and a console 3.

The scanner device 2 includes gamma ray detectors 11 and 12, two collimators 13 and 14 detachably provided on the gamma ray detectors 11 and 12, a rotary pedestal 15, a fixed pedestal 16, and a rotary drive device 21. And a data acquisition circuit 22 and a sleeper device 23.

The gamma ray detectors 11 and 12 are held on the rotary base 15. As the rotary gantry 15 rotates around a predetermined rotary axis r (around the z-axis (body axis)) via the rotary drive device 21, the two gamma ray detectors 11 and 12 integrally move around the rotary shaft r. Rotate. The rotary pedestal 15 has a rotary plate that is rotatably supported with respect to the fixed pedestal 16. The gamma ray detectors 11 and 12 are held by the rotating plate of the rotating base 15. The fixed pedestal 16 is composed of a housing fixed to the base. The rotary pedestal 15 and the fixed pedestal 16 are covered with, for example, a pedestal cover. An opening including an imaging region is provided in the central portion of the rotary pedestal 15, the fixed pedestal 16, and the pedestal cover that covers them.

The gamma ray detector 11 detects gamma rays emitted from RI (radioactive isotope) such as Tl-201 and Tc-99m administered to the subject (for example, patient) P. Since the gamma ray detector 12 has the same configuration and operation as the gamma ray detector 11, the description thereof will be omitted. The gamma ray detector 11 may be a scintillator type detector or a semiconductor type detector.

When the gamma ray detector 11 is a scintillator type detector, the gamma ray detector 11 includes a collimator 13 for defining the incident angle of the gamma ray and a scintillator that emits a momentary flash when the gamma ray collimated by the collimator 13 is incident. It also has a light guide, a plurality of photomultiplier tubes arranged in two dimensions for detecting light emitted from the scintillator, an electronic circuit for the scintillator, and the like. The scintillator is composed of, for example, thallium-activated sodium iodide NaI (Tl).

In the electronic circuit for scintillator, each time an event in which gamma rays are incident occurs, information on the incident position of gamma rays in a detection plane composed of a plurality of photomultiplier tubes based on the outputs of the plurality of photomultiplier tubes. (Position information), incident intensity information, and incident time information are generated and output to the processing circuit 35 of the console 3. This position information may be information on two-dimensional coordinates in the detection surface, or the detection surface is virtually divided into a plurality of division areas (primary cells) in advance (for example, divided into 128 × 128 pieces). However, it may be information indicating which primary cell was incident.

On the other hand, when the gamma ray detector 11 is a semiconductor type detector, the gamma ray detector 11 is a collimator 13 and a plurality of gamma ray detection semiconductors arranged in two dimensions for detecting gamma rays collimated by the collimator 13. It has an element (hereinafter referred to as a semiconductor element) and an electronic circuit for a semiconductor. The semiconductor element is composed of, for example, CdTe or CdZnTe (CZT).

Each time an event in which gamma rays are incident occurs, the semiconductor electronic circuit generates incident position information, incident intensity information, and incident time information based on the output of the semiconductor element and outputs the incident position information, the incident intensity information, and the incident time information to the processing circuit 35. This position information is information indicating which semiconductor element of a plurality of semiconductor elements (for example, 128 × 128) is incident.

That is, the gamma ray detector 11 outputs incident position information, incident intensity information, and incident time information for each event. Further, the position information is at least one of the information indicating which position of the primary cell the gamma ray is incident on and the information of the two-dimensional coordinates in the detection plane.

In the gamma ray detectors 11 and 12, the imaging timing is controlled by the processing circuit 35.

The collimators 13 and 14 are each made of a substance such as lead or tungsten that is difficult to transmit radiation, and are provided with a plurality of holes for regulating the direction in which photons fly. This hole has a polygonal shape, such as a hexagon.

The rotation drive device 21 rotates a rotating means such as a motor for rotating the rotating base 15 around a predetermined rotating shaft r at high speed, electronic parts for controlling the rotation of the rotating means, and the rotating base 15 for rotating the rotating means. It has a transmission means such as a roller for transmitting to. The rotation drive device 21 is controlled by the processing circuit 35 via the data acquisition circuit 22 to rotate the rotation base 15 around a predetermined rotation axis r. For example, the processing circuit 35 collects projection data of a subject from a plurality of directions by rotating the gamma ray detectors 11 and 12 around the subject P continuously or stepwise via a rotary gantry 15. Is possible.

The data acquisition circuit 22 is composed of, for example, a printed circuit board, and is controlled by the processing circuit 35 to control the gamma ray detectors 11 and 12, the rotation drive device 21, and the top plate drive device 25 to capture an image of the subject P. To execute.

The data acquisition circuit 22 collects the outputs of the gamma ray detectors 11 and 12 in, for example, a list mode, and outputs the collected gamma ray projection data to the console 3. In the list mode, the gamma ray detection position information, intensity information, information indicating the relative position between the gamma ray detectors 11 and 12 and the subject P (such as the position and angle of the gamma ray detectors 11 and 12), and the gamma ray detection time are displayed. Collected for each gamma ray incident event.

The sleeper device 23 has a top plate 24 and a top plate driving device 25. The subject P is placed on the top plate 24. The top plate driving device 25 is controlled by the processing circuit 35 via the data acquisition circuit 22 to move the top plate 24. Specifically, the top plate driving device 25 includes a motor as a driving source for moving the top plate 24 along the z-axis direction and the x-axis direction, electronic components for controlling the motor, and the like. Further, the top plate driving device 25 includes a motor as a driving source for raising and lowering the top plate 24, electronic components for controlling the motor, and the like.

On the other hand, the console 3 of the nuclear medicine diagnostic apparatus 1 is composed of, for example, a general personal computer or a workstation, and has an input circuit 31, a display 32, a storage circuit 33, a network connection circuit 34, and a processing circuit 35. The console 3 does not have to be provided independently. For example, a part of the configurations 31-35 of the console 3 may be provided in a distributed manner on the fixed pedestal 16.

The input circuit 31 is composed of general input devices such as a trackball, a switch button, a mouse, a keyboard, and a numeric keypad, and outputs an operation input signal corresponding to the user's operation to the processing circuit 35. For example, the user can specify the imaging target site and the RI to be used in the examination via the input circuit 31.

The display 32 is composed of a general display output device such as a liquid crystal display or an OLED (Organic Light Emitting Diode) display.

The storage circuit 33 has a configuration including a recording medium that can be read by a processor, such as a magnetic or optical recording medium or a semiconductor memory. The storage circuit 33 is controlled by the processing circuit 35 to store the count value (input count number) for each display pixel and the nuclear medicine image. Further, the storage circuit 33 stores in advance a top plate attenuation correction map 60 for correcting the attenuation of gamma rays by the top plate 24 on which the subject P is placed. Some or all of the programs and data in these recording media may be configured to be downloaded by communication via an electronic network.

The network connection circuit 34 is composed of, for example, a network card having a predetermined printed circuit board, and implements various information and communication protocols according to the form of the network. The network connection circuit 34 connects the nuclear medicine diagnostic apparatus 1 and other devices according to the various protocols. An electrical connection via an electronic network or the like can be applied to this connection. Here, the electronic network means a general information communication network using telecommunications technology, and in addition to a wireless / wired hospital backbone LAN (Local Area Network) and an Internet network, a telephone communication network, an optical fiber communication network, and a cable. Includes communication networks and satellite communication networks.

The processing circuit 35 performs a process for performing preprocessing for correcting the nuclear medicine reconstruction data to the reconstruction data suitable for the body contour extraction process by reading and executing the program stored in the storage circuit 33. The processor to run. By the preprocessing executed by the processing circuit 35, the nuclear medicine reconstruction data is corrected to the reconstruction data suitable for the body contour extraction processing. By using the nuclear medicine reconstruction data corrected by this pretreatment, a more accurate body contour can be extracted by the body contour extraction processing as compared with the case of using the reconstruction data without the pretreatment.

(Outline of pretreatment)
Next, the outline of the process for converting the nuclear medicine reconstruction data into the reconstruction data suitable for the body contour extraction process, which is executed by the processor of the processing circuit 35 according to the present embodiment, will be described. This process is executed as a pre-process of the body contour extraction process.

FIG. 2 is a schematic block diagram showing an example of a function realized by the processor of the processing circuit 35. Further, FIG. 3 is a diagram for explaining the outline of the pretreatment (process for correcting the nuclear medicine reconstruction data to the reconstruction data suitable for the body contour extraction processing) according to the present embodiment. FIG. 3 shows an example of preprocessing the reconstruction data of the SPECT reconstruction image 50 of the myocardium.

Further, FIG. 4 shows an example of a procedure for executing a process (preprocessing) for correcting the nuclear medicine reconstruction data to the reconstruction data suitable for the body contour extraction process by the processor of the processing circuit 35 shown in FIG. It is a flowchart. In FIG. 4, reference numerals with numbers attached to S indicate each step of the flowchart.

When the body contour extraction process for setting a threshold value for the count value is performed on the SPECT reconstruction image 50 of the myocardium (see the first stage in FIG. 3), when there is a region with a high count value in the reconstruction data. , It may be difficult to accurately extract the body contour because the threshold value cannot be set well due to the influence of the high count value region. Further, when RI such as Tl-201, which has a small number of input counts in the first place, is used, the success rate of body contour extraction becomes poor. In addition, the reconstruction data at the time of loading based on the projection data collected by applying a load to the myocardium of the subject P by exercise or a drug, etc., has more RI accumulation than the reconstruction data at rest, so that the body is further accumulated. The success rate of contour extraction becomes worse.

In the method of setting the threshold value for the count value, as a preprocessing for reducing the influence of the region of the high count value in the reconstructed data, a process of replacing the count value exceeding the predetermined count value with the predetermined count value can be considered. Even if the treatment is applied, it is difficult to accurately extract the body contour.

In addition, due to the effect of gamma ray attenuation by the top plate 24 on which the subject P is placed, the SPECT reconstruction data of the body part is such that the back part of the subject P (the part in contact with the top plate 24 and its surroundings) is the front side. It tends to be unclear in comparison. Therefore, the accuracy is lowered when the body contour of the back portion is extracted from the SPECT reconstruction data of the body portion.

Therefore, the processing circuit 35 according to the present embodiment improves the accuracy of extracting the body contour of the back surface of the subject P by correcting the influence of the attenuation of gamma rays by the top plate 24. Further, in order to reduce the influence of the region of the high count value, the correction is performed to relatively increase the count value in the region other than the high count value. Further, by processing the signal from the region outside the body contour as a background component, the body contour of the subject P can be accurately extracted.

In order to perform these corrections, as shown in FIG. 2, the processor of the processing circuit 35 has a reconstruction data acquisition function 41, an interest area acquisition function 42, a top plate attenuation correction map generation function 43, an alignment function 44, and mask data. The generation function 45 and the correction reconstruction data generation function 46 are realized. Each of these functions 41-46 is stored in the storage circuit 33 in the form of a program.

The realization function 41-46 of the processing circuit 35 for executing the preprocessing according to the present embodiment may be independently provided as a preprocessing program, or the SSPAC processing device 101 or the contour extraction filter processing device. It may be incorporated and used in a program such as a body contour extraction processing program of an apparatus such as 102.

The reconstruction data acquisition function 41 acquires reconstruction data based on gamma rays emitted from the subject P (step S1 in FIG. 4). Further, the reconstruction data acquisition function 41 generates a reconstruction image 50 (see the first stage in FIG. 3) based on the acquired reconstruction data and displays it on the display 32.

Specifically, the reconstruction data acquisition function 41 acquires reconstruction data by generating reconstruction data based on the projection data of the subject P acquired via the data acquisition circuit 22. In this case, the scanner device 2 scans the subject P based on the scan plan, so that the projection data based on the gamma rays emitted from the RI administered to the subject P is regenerated via the data acquisition circuit 22. It is given to the configuration data acquisition function 41.

Further, the reconstruction data acquisition function 41 is transmitted from an external medical image storage device such as an image server of a PACS (Picture Archiving and Communication System) connected via a network via a network connection circuit 34. And the reconstruction data may be acquired.

The region of interest acquisition function 42 acquires the region of interest 51 (see the second stage in FIG. 3) corresponding to the body contour of the subject P, which is set for the reconstruction data based on the projection data of the subject P (see the second stage of FIG. 3). Step S2 in FIG. 4). In the following description, an example in which the region of interest 51 has an elliptical shape will be described. In this case, the region of interest 51 may be set as a rough ellipse including the body contour. Further, in this case, the region of interest acquisition function 42 may store information about the set ellipse, such as information on the center position, minor axis, and major axis of the set ellipse, in the storage circuit 33.

The region of interest 51 is set by the user, for example, via the input circuit 31 while checking the reconstructed image 50 displayed on the display 32. Further, the region of interest acquisition function 42 may read a preset template from the storage circuit 33 and acquire this template as the region of interest 51.

The top plate attenuation correction map generation function 43 previously prepares a top plate attenuation correction map 60 (see the left side of the third row in FIG. 3) for correcting the influence of gamma ray attenuation by the top plate 24 on which the subject P is placed. It is generated and stored in the storage circuit 33. Using the top plate attenuation correction map 60, reconstruction data is created in which the influence of gamma ray attenuation by the top plate 24 is corrected. By using this corrected reconstruction data, a device that performs body contour extraction processing such as the SSPAC processing device 101 and the contour extraction filter processing device 102 can accurately extract the body contour of the back surface of the subject P. ..

The alignment function 44 aligns the region of interest 51 with the top plate attenuation correction map 60. A top plate attenuation correction process including a specific method for generating the top plate attenuation correction map 60 and a method for aligning the top plate attenuation correction map 60 will be described later with reference to FIGS. 7-9.

The mask data generation function 45 generates mask data 71 (see the right side of the third row in FIG. 3) having a higher weight than the reconstruction data on the center side with respect to the reconstruction data on the edge side inside the region of interest 51. .. By correcting the reconstruction data using the mask data 71, the count value in the region other than the high count value can be relatively increased, and the influence of the region of the high count value can be reduced. Further, by correcting the reconstruction data using the mask data 71, it is possible to process the signal from the region outside the body contour as a background component. The mask data correction process including the specific method for generating the mask data 71 will be described later with reference to FIGS. 10-12.

The correction reconstruction data generation function 46 corrects the reconstruction data based on the top plate attenuation correction map 60 (step S3 in FIG. 4) and corrects the reconstruction data based on the mask data 71 (FIG. 4). Step S4), the correction reconstruction data is generated. The correction reconstruction data generation function 46 may generate the correction reconstruction image 80 based on the generated correction reconstruction data (see the fourth stage of FIG. 3). One of the correction of the reconstruction data based on the top plate attenuation correction map 60 and the correction of the reconstruction data based on the mask data 71 may be omitted.

Then, the correction reconstruction data generation function 46 uses the generated correction reconstruction data to perform body contour extraction processing such as the SSPAC processing device 101 that executes the SSPAC method and the contour extraction filter processing device 102 that executes the contour extraction filter processing. Output to an external device. The SSPAC processing device 101 and the contour extraction filter processing device 102 use the reconstruction data without preprocessing by performing the body contour extraction processing using the correction reconstruction data generated by the preprocessing executed by the processing circuit 35. Compared to the case, it is possible to extract a more accurate body contour.

According to the nuclear medicine diagnostic apparatus 1 according to the present embodiment, the user only roughly sets the region of interest 51 including the body contour, and the correction suitable for the body contour extraction process is performed without performing other complicated work. Reconstruction data can be easily generated.

Subsequently, a modified example of the method of setting the region of interest 51 will be described.

FIG. 5 is an explanatory diagram showing an example of how the region of interest 51 is set when the scattered radiation reconstruction image 50S and the main reconstruction image 50M of the same slice are displayed in parallel. Further, FIG. 6 is an explanatory diagram showing an example of a method of setting a sub-window corresponding to the scattered radiation reconstruction image 50S and a main window corresponding to the main reconstruction image 50M. Although FIG. 6 shows an example when the RI is Tc-99m, the same processing can be performed with other RIs such as Tl-201.

FIG. 3 shows an example in which the region of interest 51 is set based on one reconstructed image 50, but as shown in FIG. 5, the scattered ray reconstructed image 50S and the main reconstructed image 50M of the same slice are shown. Are displayed in parallel, and the region of interest 51 may be set based on these images. In this case, the reconstruction data acquisition function 41 is based on gamma rays having energy belonging to the main window (photopeak window) of a predetermined width (for example, ± 10% of the peak energy) including the energy peak of RI for one slice. The main reconstruction data and the scattered ray reconstruction data based on the gamma rays of the Compton scattering region belonging to the subwindow of a predetermined width (for example, 7% of the peak energy) set on the lower energy side of the main window are acquired (for example). (See FIG. 6).

When the scattered radiation reconstruction image 50S and the main reconstruction image 50M of the same slice are displayed in parallel on the display 32, the user can set the region of interest 51 for either one. Here, the scattered ray reconstructed image 50S is an image in which the count value is small and the organ is difficult to see, but the body contour is easy to confirm, while the main reconstructed image 50M is an image in which the body contour is hard to see, but the organ. It is known that the image is easy to confirm the arrangement. Therefore, the user may set the region of interest 51 for the scattered radiation reconstructed image 50S while confirming the position of the organ on the main reconstructed image 50M.

The slice to be displayed may be a slice corresponding to the reconstructed image in which the region of interest 51 can be easily set. Further, the region of interest 51 set for one slice can be applied to all other slices.

Further, at this time, the interest region acquisition function 42 may display the interest region 51 set for the scattered radiation reconstruction image 50S on the main reconstruction image 50M (see FIG. 5). In this case, the user can easily confirm on the main reconstructed image 50M whether or not the region of interest 51 set for the scattered radiation reconstructed image 50S is really placed at the correct position. When only one of the scattered radiation reconstruction image 50S and the main reconstruction image 50M of the same slice exists, the user may set the region of interest 51 using only one of them.

(Top plate attenuation correction processing)
Subsequently, the reconstruction data correction process (top plate attenuation correction process) using the top plate attenuation correction map 60 executed in step S3 of FIG. 4 will be described with reference to FIG. 7-9.

FIG. 7 is a subroutine flowchart showing an example of the procedure of the top plate attenuation correction process executed in step S3 of FIG. Further, FIG. 8A is an explanatory diagram showing an example of the original data 61 including the estimated region of the top plate 24, and FIG. 8B is an explanatory diagram showing an example of the attenuation distribution map 62 of the top plate 24. , (C) are explanatory views showing an example of the top plate attenuation correction map 60. Further, FIG. 9 is an explanatory diagram showing an example of the alignment of the region of interest 51 and the top plate attenuation correction map 60.

First, in step S31, the top plate attenuation correction map generation function 43 generates the original data 61 including the region of the top plate 24. The region of the top plate 24 may be generated by simulation as shown in FIG. 8A, for example, or may be extracted from a pre-collected X-ray CT image.

Next, in step S32, the top plate attenuation correction map generation function 43 generates the attenuation distribution map 62 of the top plate 24 based on the original data 61 (see FIG. 8B).

Next, in step S33, the top plate attenuation correction map generation function 43 uses the top plate attenuation correction map (top plate attenuation correction map) for correcting the influence of gamma ray attenuation by the top plate 24 represented by the attenuation distribution map 62 of the top plate 24. (Distribution of attenuation correction data of the plate 24) 60 is generated (see FIG. 8C) and stored in the storage circuit 33.

Next, in step S34, the alignment function 44 performs the interest region 51 and the top plate attenuation correction map 60 so that the center of the upper surface of the top plate 24 and the center of the lower end of the interest region 51 in the top plate attenuation correction map 60 coincide with each other. And automatically align. For example, when the region of interest 51 has an elliptical shape, as shown in FIG. 9, in the alignment function 44, the lower end 52 of the minor axis of the ellipse coincides with the center 64 of the upper surface of the top plate 24 in the top plate attenuation correction map 60. Align as it does. When the region of the top plate 24 is extracted from the X-ray CT image, care should be taken so that the size (pixel size) of the top plate 24 and the position in the X-ray CT image match. By aligning in this way, it is possible to reproduce the appearance in which the subject P having the body contour presumed to correspond to the region of interest 51 is placed in the center of the top plate 24 in the width direction.

If there is a part where the original data does not exist due to the alignment, 1.0 may be set in this part. By multiplying by 1.0, it is possible to prevent the top plate attenuation correction processing for the relevant portion.

Next, in step S35, the correction reconstruction data generation function 46 corrects the reconstruction data by multiplying the top plate attenuation correction map 60 by the reconstruction data corresponding to the reconstruction image 50. When the scattered radiation reconstruction image 50S is available and the region of interest 51 is set for the scattered radiation reconstruction image 50S, the correction reconstruction data generation function 46 reconstructs the top plate attenuation correction map 60. It is advisable to multiply the scattered radiation reconstruction data corresponding to the constituent image 50S.

By the above procedure, the influence of the attenuation of gamma rays by the top plate 24 included in the reconstruction data can be corrected.

The top plate 24 is not depicted in the reconstructed image 50 because it is not the origin of the scattered rays, but it is included in the effective field of view. Therefore, the reconstructed data is affected by the attenuation of gamma rays by the top plate 24.

According to the nuclear medicine diagnostic apparatus 1 according to the present embodiment, the reconstruction data can be corrected so as to reduce the influence of the attenuation of gamma rays by the top plate 24 by the top plate attenuation correction process shown in FIG. 7. Therefore, the reconstruction data after the top plate attenuation correction processing generated in step S35 is the data in which the ambiguity of the back surface portion (the portion in contact with the top plate 24 and its surroundings) of the subject P is eliminated. be. Therefore, the device that performs the body contour extraction process, such as the SSPAC processing device 101 and the contour extraction filter processing device 102, uses the reconstruction data after the top plate attenuation correction process generated by the nuclear medicine diagnostic device 1 according to the present embodiment. As a result, the body contour of the back surface of the subject P can be easily and accurately extracted as compared with the case of using the reconstructed data without the correction.

(Mask data correction processing)
Subsequently, the reconstruction data correction process (mask data correction process) using the mask data 71 of the region of interest 51 executed in step S4 of FIG. 4 will be described with reference to FIGS. 10-12.

According to the mask data correction process, it is possible to reduce the influence of the high count value region by lifting the data on the edge side inside the region of interest 51. Further, according to the mask data correction processing, the signal outside the region of interest 51 can be processed as a background component (noise component).

FIG. 10 is a subroutine flowchart showing an example of the procedure of the mask data correction process executed in step S4 of FIG. Further, FIG. 11A is an explanatory diagram showing a first example of the mask data 71, FIG. 11B is an explanatory diagram showing a second example of the mask data 71, and FIG. 11C is a third example of the mask data 71. It is explanatory drawing which shows.

In step S41, the mask data generation function 45 has a higher weight than the reconstructed data on the central side with respect to the reconstructed data on the peripheral side inside the region of interest 51 (as if lifting the data on the peripheral side). , The portion corresponding to the inside of the region of interest 51 of the mask data 71 is set.

In the first example of the mask data 71 shown in FIG. 11A, the profile 70v in the vertical direction (minor radial direction) and the profile 70h in the horizontal direction (major axis direction) are each in the region of interest 51 inside the region of interest 51. This is an example in which the center of the region 51 is the lowest value, the boundary (contour) of the region of interest 51 is the highest value, and the center and the boundary are connected by a straight line.

The second example of the mask data 71 shown in FIG. 11B is first in that each of the vertical profile 70v and the horizontal profile 70h has a shape having a predetermined width as the minimum value from the center of the region of interest 51. Different from one example. In the third example of the mask data 71 shown in FIG. 11C, each of the vertical profile 70v and the horizontal profile 70h is directed toward the center from the boundary (contour) of the region of interest 51 inside the region of interest 51. This is an example of having the shape of a so-called Butterworth Filter. The profile of the mask data 71 is not limited to the shapes illustrated in the first to third examples.

The minimum and maximum values of the profile 70v in the vertical direction may be set to be the same as the minimum and maximum values of 70h in the horizontal direction, respectively. In this case, the mask value on the boundary (contour) of the region of interest 51 becomes uniform over the entire circumference.

Next, in step S42, the mask data generation function 45 increases the mask data 71 so that the outside of the boundary of the region of interest 51 becomes zero or approaches zero according to the distance from the boundary of the region of interest 51. A portion corresponding to the outside of the region of interest 51 of is set.

The first to third examples of the mask data 71 shown in FIGS. 11A, 11B, and 11C are all examples in which the outside of the boundary of the region of interest 51 is set to zero.

FIG. 12 is an explanatory diagram showing an example of mask data 71 set to approach zero according to the distance from the boundary of the region of interest 51. FIG. 12 shows the profile 71h in the horizontal direction (major axis direction), but the profile 71v in the vertical direction (minor axis direction) also has a similar shape. FIG. 12 shows an example in which the profile 71hi corresponding to the inside of the region of interest 51 has the same shape as the third example shown in FIG. 11 (c).

As shown in FIG. 12, the lateral profile 71h of the region of interest 51 having an elliptical shape with a major axis length of 2a is a distance from the boundary of the region of interest 51 in the profile 71he corresponding to the outside of the region of interest 51. It may be set to approach zero accordingly.

Then, in step S43, the correction reconstruction data generation function 46 corrects the reconstruction data by multiplying the reconstruction data corresponding to the reconstruction image 50 by the mask data 71.

By the above procedure, the reconstruction data can be corrected by using the mask data 71.

The nuclear medicine diagnostic apparatus 1 according to the present embodiment can correct the reconstructed data by using the mask data 71 as illustrated in FIGS. 11 and 12. The reconstruction data after the mask data correction process generated in step S43 is data in which the count value of the edge portion of the region of interest 51 is relatively increased (raised) as compared with the vicinity of the center of the region of interest 51.

Therefore, the device that performs the body contour extraction process, such as the SSPAC processing device 101 and the contour extraction filter processing device 102, uses the reconstructed data after the mask data correction process generated by the nuclear medicine diagnostic device 1 according to the present embodiment. Therefore, as compared with the case of using the reconstructed data without the correction, it is less likely to be affected by the region of the high count value, and the body contour of the subject P can be extracted more accurately.

Further, the mask data 71 is such that the profile corresponding to the outside of the region of interest 51 becomes zero outside the boundary of the region of interest 51, or approaches zero according to the distance from the boundary of the region of interest 51. Set. Therefore, the signal derived from the outside of the region of interest 51, that is, the portion presumed to be outside the subject P can be processed as a background component (noise component), and the extraction accuracy of the body contour can be further improved. Can be done.

Further, as shown in FIG. 12, when the profile 71he corresponding to the outside of the region of interest 51 is set to approach zero according to the distance from the boundary of the region of interest 51, the regions of interest 51 of the profiles 71h and 71v The shape at the boundary of is made smooth. Therefore, as compared with the case where the profiles 71he are all zero, the influence of the shape of the region of interest 51 can be reduced in the body contour extraction processing performed later. Therefore, even when the region of interest 51 is simply and roughly set by the user, the device that performs the body contour extraction process accurately extracts the body contour without being affected by the shape of the region of interest 51. Can be done.

FIG. 13A is an explanatory diagram showing an example of a body contour extracted using the reconstructed data not subjected to the pretreatment according to the present embodiment, and FIG. 13B is an explanatory diagram showing an example of the body contour extracted using the reconstruction data not subjected to the pretreatment according to the present embodiment. It is explanatory drawing which shows an example of the body contour extracted using the corrected reconstruction data.

As is clear by comparing FIGS. 13 (a) and 13 (b), by using the corrected reconstruction data subjected to the pretreatment according to the present embodiment, the SSPAC processing device 101, the contour extraction filter processing device 102, and the like can be used. The device that performs the body contour extraction process can extract the body contour of the subject P very accurately.

According to at least one embodiment described above, preprocessing for correcting nuclear medicine reconstruction data to reconstruction data suitable for body contour extraction processing can be performed.

The region of interest acquisition function 42, the alignment function 44, the mask data generation function 45, and the correction reconstruction data generation function 46 of the processing circuit 35 in the present embodiment are the region of interest acquisition unit and the alignment within the scope of the claims, respectively. This is an example of a unit, a mask data generation unit, and a correction reconstruction data generation unit. Further, the storage circuit 33 in the present embodiment is an example of a storage unit within the scope of the claims.

Further, in the above embodiment, the word "processor" refers to, for example, a dedicated or general-purpose CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or an application specific integrated circuit (ASIC). It shall mean a circuit such as a programmable logic device (for example, a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and an FPGA). The processor realizes various functions by reading and executing a program stored in a storage medium.

Further, in the above embodiment, an example in which a single processor of the processing circuit realizes each function has been shown, but a plurality of independent processors are combined to form a processing circuit, and each processor realizes each function. May be good. When a plurality of processors are provided, the storage medium for storing the program may be provided individually for each processor, or one storage medium collectively stores the programs corresponding to the functions of all the processors. May be good.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... Nuclear medicine diagnostic device 24 ... Top plate 42 ... Area of interest acquisition function 44 ... Alignment function 45 ... Mask data generation function 46 ... Correction reconstruction data generation function 50 ... Reconstruction image 50M ... Main reconstruction image 50S ... Scattered rays Reconstructed image 51 ... Area of interest 60 ... Top plate attenuation correction map 62 ... Attenuation distribution map 71 ... Mask data 80 ... Corrected reconstruction image

Claims (7)

It is a nuclear medicine diagnostic device that corrects reconstruction data based on gamma rays so that it becomes reconstruction data suitable for contour extraction processing that extracts body contours.
An area of interest acquisition unit that acquires an area of interest corresponding to the body contour of the subject, which is set for reconstruction data based on gamma rays emitted from the subject.
A storage unit that stores a top plate attenuation correction map for correcting the attenuation of gamma rays by the top plate on which the subject is placed, and a storage unit.
An alignment unit that aligns the region of interest with the top plate attenuation correction map, and
A mask data generation unit that generates mask data having a higher weight than the reconstruction data on the center side with respect to the reconstruction data on the edge side in the region of interest.
A correction reconstruction data generation unit that generates correction reconstruction data by correcting the reconstruction data based on the top plate attenuation correction map and the mask data.
Nuclear medicine diagnostic equipment equipped with. The alignment part is
The region of interest and the top plate attenuation correction map are aligned so that the center of the upper surface of the top plate in the top plate attenuation correction map coincides with the center of the lower end of the region of interest.
The nuclear medicine diagnostic apparatus according to claim 1. The mask data generation unit
The mask data is generated so that the reconstructed data outside the region of interest becomes zero or approaches zero depending on the distance from the boundary of the region of interest.
The nuclear medicine diagnostic apparatus according to claim 1 or 2. The top plate attenuation correction map is
The region of the top plate is generated by simulation, or the region of the top plate is extracted from the X-ray CT image collected in advance, and the attenuation distribution map of the top plate is generated based on the region of the top plate. Generated to correct the effect of gamma ray attenuation by the top plate represented by this top plate attenuation distribution map.
The nuclear medicine diagnostic apparatus according to any one of claims 1 to 3. The correction reconstruction data generation unit
The correction reconstruction data is output to the apparatus that performs the contour extraction process.
The nuclear medicine diagnostic apparatus according to any one of claims 1 to 4. The area of interest acquisition unit
Of the gamma rays emitted from the subject, for the scattered radiation reconstruction image generated based on the scattered radiation reconstruction data based on the gamma rays in the Compton scattering region belonging to the subwindow set on the energy peak side of the energy peak. To acquire the area of interest set in
The nuclear medicine diagnostic apparatus according to any one of claims 1 to 5. The correction reconstruction data generation unit
The corrected reconstruction data is generated by correcting the scattered radiation reconstruction data based on the top plate attenuation correction map and the mask data.
The nuclear medicine diagnostic apparatus according to claim 6.

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