Nuclear Medicine Diagnostic Equipment

Abstract

To provide a nuclear medicine diagnostic apparatus capable of preventing an excess current in detector units.SOLUTION: A nuclear medicine diagnostic apparatus includes a top board 11, a plurality of detector units 14a, a collection section, and a control section. A subject P dosed with a radioisotope is placed on the top board. The detector units detect a gamma ray emitted from the subject by the radioisotope. The collection section collects current information which indicates current flowing in each one of the detector units by the gamma ray to be emitted when the subject is placed at a first position. The control section controls the position of the top board based on the current information so as to move the subject from the first position to a second position.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The embodiments disclosed in this specification and the drawings relate to a nuclear medicine diagnostic device. [Background technology]

[0002] Conventionally, PET (Positron Emission Tomography) devices detect gamma rays emitted when a positron emitted from a radioisotope (RadioIsotope: RI) administered to a subject annihilates with an electron, and reconstruct a PET image based on the detected gamma rays.

[0003] Generally, a PET device is equipped with multiple detector units for detecting gamma rays, but depending on the type of RI administered to the subject and the position of the subject when imaging is performed, gamma rays may concentrate on a specific detector unit, which may cause an overcurrent in the detector unit. Note that such an overcurrent in the detector unit is not limited to PET devices, but may also occur in other nuclear medicine diagnostic devices. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 7,693,565 Summary of the Invention [Problem to be solved by the invention]

[0005] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to prevent an overcurrent in the detector unit. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described later can also be positioned as other problems. [Means for solving the problem]

[0006] A nuclear medicine diagnosis apparatus according to an embodiment includes a top plate, a plurality of detector units, a collection unit, and a control unit. A subject administered with a radioisotope is placed on the top plate. The plurality of detector units detect gamma rays emitted from the subject by the radioisotope. The collection unit collects current information indicating a current flowing through each detector unit due to gamma rays emitted when the subject is placed at a first position. The control unit moves the subject from the first position to a second position by controlling the position of the top plate based on the current information. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a PET apparatus according to the first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of the configuration of the detector unit according to the first embodiment. [Diagram 3] FIG. 3 is a diagram showing an example of the movement of the subject performed by the bed control circuitry according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing an example of the movement of the subject performed by the bed control circuitry according to the first embodiment. [Diagram 5] FIG. 5 is a flowchart illustrating an example of processing performed by the current information collecting circuit and the bed control circuit according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing an example of current estimation performed by the current information collecting circuit according to the second embodiment. [Figure 7] FIG. 7 is a diagram showing an example of current estimation performed by the current information collecting circuit according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of a nuclear medicine diagnosis apparatus will be described in detail with reference to the drawings. Note that, in the following, an embodiment of a PET apparatus will be described as an example of the nuclear medicine diagnosis apparatus.

[0009] (First embodiment) FIG. 1 is a diagram showing an example of the configuration of a PET apparatus according to the first embodiment.

[0010] The PET device 100 according to this embodiment detects gamma rays emitted by annihilation of a positron emitted from an RI administered to a subject P with an electron, and reconstructs a PET image based on the detected gamma rays.

[0011] For example, as shown in FIG. 1, a PET device 100 according to this embodiment includes a gantry device 10 and a console device 20.

[0012] The gantry 10 detects gamma rays emitted from the subject P when positrons emitted by RI administered to the subject P annihilate with electrons, and collects counting information by counting the detected gamma rays. Here, the gantry 10 has a cylindrical opening formed to penetrate the gantry 10 in the horizontal direction, and detects gamma rays emitted from the subject P placed at the opening.

[0013] In this embodiment, the direction along the axis of the cylindrical opening of the gantry device 10 is defined as the Z-axis direction, the horizontal direction perpendicular to the Z-axis direction is defined as the X-axis direction, and the vertical direction perpendicular to the Z-axis direction is defined as the Y-direction.

[0014] Specifically, the gantry 10 includes a tabletop 11 , a bed 12 , a bed driving mechanism 13 , a PET detector 14 , a counting information collecting circuit 15 , a current information collecting circuit 16 , and a bed control circuit 17 .

[0015] The top board 11 is a bed on which the subject P who has been administered RI is placed. For example, the top board 11 is formed in a rectangular flat plate shape and is disposed so that the longitudinal direction is parallel to the Z-axis direction.

[0016] The bed 12 supports the top board 11 so as to be movable in the X-axis direction, the Y-axis direction, and the Z-axis direction.

[0017] The bed driving mechanism 13 is provided inside or outside the bed 12, and moves the top board 11 supported by the bed 12. For example, when imaging the subject P, the bed driving mechanism 13 moves the top board 11 on which the subject P is placed to an opening of the gantry device 10. For example, the bed driving mechanism 13 moves the top board 11 on the bed 12 while the position of the bed 12 is fixed. Alternatively, for example, the bed driving mechanism 13 moves the bed 12 arranged on a moving base together with the top board 11.

[0018] The PET detector 14 detects gamma rays emitted from the subject P by the RI administered to the subject P, converts the detected gamma rays into an electrical signal, and outputs it.

[0019] Specifically, the PET detector 14 includes a plurality of detector units 14a, and each detector unit 14a detects gamma rays emitted from the subject P. Here, the plurality of detector units 14a are arranged in a circumferential direction centered on the Z axis so as to surround an opening formed in the gantry device 10. Also, each of the plurality of detector units 14a includes a plurality of detector modules, and each detector module detects gamma rays.

[0020] FIG. 2 is a diagram showing an example of the configuration of the detector unit 14a according to the first embodiment.

[0021] 2, the detector unit 14a includes a plurality of detector modules 14b arranged in the Z-axis direction. Each detector module 14b has a plurality of gamma ray detection elements arranged two-dimensionally along the circumferential direction and the Z-axis direction of the PET detector 14, for example, and each gamma ray detection element detects gamma rays emitted from the subject P.

[0022] 1, the counting information collecting circuit 15 collects counting information by counting gamma rays based on the electrical signals output from each detector unit 14a of the PET detector 14. Specifically, the counting information collecting circuit 15 converts the electrical signals output from the PET detector 14 into digital signals to generate counting information including the detection position, energy value, and detection time of the gamma rays. Then, the counting information collecting circuit 15 stores the generated counting information in the memory 23.

[0023] The current information collecting circuit 16 and the bed control circuit 17 will be described in detail later.

[0024] The console device 20 receives various operations for the PET device 100 from an operator, and controls the operation of the PET device 100 based on the received operations. Specifically, the console device 20 includes an input interface 21, a display 22, a memory 23, and a processing circuit 24. Here, each unit included in the console device 20 is connected via a bus. Note that, although an example in which the gantry device 10 and the console device 20 are separate entities will be described here, the console device 20 or some of the components of the console device 20 may be included in the gantry device 10.

[0025] The input interface 21 receives various input operations from an operator, converts the received input operations into electrical signals, and outputs the electrical signals to the processing circuit 24. For example, the input interface 21 is realized by a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touchpad for performing input operations by touching an operation surface, a touch screen in which a display screen and a touchpad are integrated, a non-contact input circuit using an optical sensor, a voice input circuit, and the like for setting imaging conditions and a region of interest (ROI), and the like. Note that, for example, the input interface 21 may be provided in the gantry device 10. Also, for example, the input interface 21 may be configured by a tablet terminal or the like capable of wireless communication with the main body of the console device 20. Also, the input interface 21 is not limited to only those having physical operation parts such as a mouse and a keyboard. For example, an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the console device 20 and outputs the electrical signal to the processing circuit 24 is also included in the input interface 21.

[0026] The display 22 displays various information. For example, the display 22 outputs a PET image generated by the processing circuit 24, a GUI (Graphical User Interface) for receiving various operations from an operator, and the like. For example, the display 22 is a liquid crystal display or a CRT (Cathode Ray Tube) display. Note that, for example, the display 22 may be provided in the gantry device 10. Also, for example, the display 22 may be a desktop type, or may be configured as a tablet terminal or the like capable of wireless communication with the console device 20 main body.

[0027] The memory 23 stores various data used in the PET device 100. For example, the memory 23 is realized by a semiconductor memory element such as a random access memory (RAM) or a flash memory, a hard disk, an optical disk, or the like.

[0028] The processing circuitry 24 controls the overall operation of the PET device 100. Specifically, the processing circuitry 24 has a coincidence counting information generating function 24a, a reconstruction function 24b, and a control function 24c.

[0029] The coincidence information generating function 24a generates coincidence information using the counting information collected by the counting information collecting circuit 15. Specifically, the coincidence information generating function 24a refers to the counting information stored in the memory 23, and searches for a set of counting information in which gamma rays are counted substantially simultaneously, based on the detection time of each piece of counting information. Then, the coincidence information generating function 24a generates coincidence information that associates the searched sets of counting information, and stores the generated coincidence information in the memory 23.

[0030] The reconstruction function 24b reconstructs a PET image based on the coincidence information generated by the coincidence information generating function 24a. Specifically, the reconstruction function 24b reads out the coincidence information stored in the memory 23, and performs back projection processing using the read out coincidence information as projection data, thereby reconstructing the PET image. The reconstruction function 24b also stores the reconstructed PET image in the memory 23.

[0031] The control function 24c performs overall control of the PET device 100 by controlling each part of the gantry device 10 and the console device 20. For example, the control function 24c controls the bed control circuit 17 to operate the bed driving mechanism 13 provided inside or outside the bed 12, thereby controlling the position of the tabletop 11. Also, for example, the control function 24c controls the counting information collecting circuit 15 to collect counting information of gamma rays emitted from the subject P.

[0032] An example of the configuration of the PET device 100 according to this embodiment has been described above.

[0033] Generally, in a PET device, depending on the type of RI administered to the subject and the position of the subject when imaging is performed, gamma rays may concentrate on a specific detector unit, which may cause an overcurrent in the detector unit.

[0034] For example, Rb-82 (rubidium chloride), which is used in cardiac PET examinations, has the characteristic of accumulating in the heart. Therefore, in cardiac PET examinations, gamma rays may concentrate on a detector unit located near the heart, causing an overcurrent. In addition, for example, if the subject moves during imaging and the subject moves to one side within the opening of the gantry, gamma rays may concentrate on a detector unit close to the subject, causing an overcurrent.

[0035] In order to prevent such an overcurrent in the detector unit, for example, a method of limiting the current by lowering the gain by lowering the voltage when the current value flowing through the detector unit exceeds an allowable value is conceivable. However, in such a method of limiting the current by lowering the gain, the linearity of the detected gamma rays may be lost, which may affect the quantitativeness of the PET image.

[0036] For this reason, the PET apparatus 100 according to this embodiment is configured to be able to prevent an overcurrent in the detector unit 14a.

[0037] Specifically, the current information collecting circuit 16 of the gantry device 10 collects current information indicating a current flowing through each detector unit 14a due to gamma rays emitted when the subject P is placed at the first position. In addition, the bed control circuit 17 of the gantry device 10 controls the position of the tabletop 11 based on the current information collected by the current information collecting circuit 16, thereby moving the subject P from the first position to the second position. Here, the current information collecting circuit 16 is an example of a collecting unit. In addition, the bed control circuit 17 is an example of a control unit.

[0038] The current information collecting circuit 16 and the bed control circuit 17 of the gantry device 10 according to this embodiment will be described in detail below.

[0039] In this embodiment, before data collection of the subject P, the current information collecting circuit 16 collects information on a current flowing through each detector unit 14a due to gamma rays emitted when the subject P is placed at an initial position within the opening of the gantry 10. Here, for example, the initial position is the center position within the opening of the gantry 10.

[0040] Specifically, the current information collecting circuit 16 collects current information indicating the current flowing through each detector unit 14a due to gamma rays emitted when the subject P is placed at an initial position within the opening of the gantry device 10.

[0041] More specifically, the current information collection circuit 16 collects current information by actually measuring the current flowing through each detector unit 14a due to gamma rays emitted from the subject P, which is placed at an initial position within the opening of the gantry device 10, after the subject P is administered an RI.

[0042] For example, the current information collecting circuit 16 collects current information by using a current sensor or the like to actually measure the current consumed when each detector unit 14a detects gamma rays.

[0043] Here, the current information collection circuit 16 collects current information for each detector unit 14a by calculating the statistical value of the current flowing through the multiple detector modules 14b included in each detector unit 14a as the current value flowing through the detector unit 14a.

[0044] For example, the current information collection circuit 16 collects current information for each detector unit 14a by calculating the average or maximum value of the current flowing through the multiple detector modules 14b included in each detector unit 14a as the current value flowing through the detector unit 14a.

[0045] In this embodiment, before data collection of the subject P is performed, the bed control circuit 17 controls the position of the tabletop 11 based on the current information collected by the current information collection circuit 16, thereby moving the subject P from its initial position within the opening of the gantry device 10 to a position where the current distribution in the multiple detector units 14a is approximately uniform.

[0046] Specifically, the bed control circuit 17 controls the position of the tabletop 11 based on the current information collected by the current information collecting circuit 16, thereby moving the subject P so that the current distribution in the multiple detector units 14a approaches a uniform state. Here, the bed control circuit 17 controls the position of the tabletop 11 by operating a bed driving mechanism 13 provided inside or outside the bed 12.

[0047] More specifically, the bed control circuitry 17 moves the subject P in a direction along a plane perpendicular to the Z-axis. The bed control circuitry 17 also stores position information indicating the position of the tabletop 11 after the subject P has been moved.

[0048] 3 and 4 are diagrams showing an example of the movement of the subject P performed by the bed control circuitry 17 according to the first embodiment.

[0049] 3 and 4 show an example of a case where a cardiac PET examination is performed, with Fig. 3 showing the state before the subject P is moved by the bed control circuit 17, and Fig. 4 showing the state after the subject P is moved by the bed control circuit 17. In addition, in Figs. 3 and 4, each of the multiple detector units 14a is patterned according to the amount of current consumption of each detector unit 14a, with a darker pattern indicating a larger current consumption.

[0050] As described above, Rb-82 used in the PET examination of the heart has a characteristic of accumulating in the heart. Therefore, in the PET examination of the heart, for example, as shown in Fig. 3, gamma rays may concentrate on the detector unit 14a located near the heart H, causing an overcurrent. In this case, the bed control circuit 17 moves the subject P in a direction from the detector unit 14a consuming a large current toward the detector unit 14a consuming a small current along a plane perpendicular to the Z axis, for example, as shown in Fig. 4.

[0051] For example, the bed control circuit 17 calculates the movement direction and movement amount of the tabletop 11 along a plane perpendicular to the Z axis so that the current distribution in the multiple detector units 14a approaches a uniform state based on the current information of each detector unit 14a collected by the current information collecting circuit 16. Then, the bed control circuit 17 moves the tabletop 11 according to the calculated movement direction and movement amount, thereby moving the subject P in a direction along the plane perpendicular to the Z axis.

[0052] As a specific example, for example, the bed control circuit 17 calculates the center of gravity of the distribution of current values ​​obtained by assigning each current value to the spatial position of each detector unit 14a based on the current value of each detector unit 14a collected by the current information collecting circuit 16. As a result, for example, in the example shown in FIG. 3, the position of the heart H of the subject P is calculated as the center of gravity. Then, the bed control circuit 17 calculates a vector whose starting point is the calculated center of gravity and whose ending point is the intersection of the perpendicular line from the center of gravity to the Z axis and the Z axis. After that, the bed control circuit 17 moves the tabletop 11 along the calculated vector, thereby moving the subject P in a direction along a plane perpendicular to the Z axis. As a result, for example, in the example shown in FIG. 4, the tabletop 11 is moved so that the heart H of the subject P is located on the Z axis. As a result, the distribution of current in the multiple detector units 14a becomes approximately uniform.

[0053] Moreover, while moving the subject P, the bed control circuitry 17 stores in the memory 23 position information indicating the position of the top board 11 after the subject P has been moved. Here, the position information of the top board 11 stored by the bed control circuitry 17 is used when reconstructing a PET image.

[0054] Specifically, the reconstruction function 24b reconstructs a PET image based on the gamma rays detected by the multiple detector units 14a after the subject P is moved, taking into account the position information of the top board 11. Here, the reconstruction function 24b is an example of a reconstruction unit.

[0055] For example, the reconstruction function 24b uses position information of the tabletop 11 stored in the memory 23 by the bed control circuit 17 to correct the position of the annihilation event calculated from the coincidence information generated by the coincidence information generation function 24a, and reconstructs a PET image based on the corrected coincidence information.

[0056] The processing functions of the processing circuitry 24 have been described above, but for example, the processing circuitry 24 is realized by a processor. In this case, the processing functions of the processing circuitry 24 are stored in the memory 23 in the form of programs executable by a computer. The processing circuitry 24 then realizes the processing functions corresponding to each program by reading and executing each program from the memory 23. In other words, the processing circuitry 24 has each processing function shown in the processing circuitry 24 in FIG. 1 when each program is read.

[0057] For example, the current information collecting circuit 16 and the bed control circuit 17 are also realized by a processor. In this case, the processing functions of the current information collecting circuit 16 and the bed control circuit 17 are stored in the memory 23 in the form of programs executable by a computer. Then, the current information collecting circuit 16 and the bed control circuit 17 realize the processing functions corresponding to each program by reading and executing each program from the memory 23.

[0058] FIG. 5 is a flowchart showing an example of processing performed by the current information collecting circuit 16 and the bed control circuit 17 according to the first embodiment.

[0059] For example, as shown in FIG. 5, after a subject P administered with an RI is placed at the center of the opening of the gantry device 10, the current information collection circuit 16 collects the current value of the current flowing through each detector unit 14a due to gamma rays emitted from the subject P in response to instructions from an operator, etc. (step S1).

[0060] Furthermore, after the current values ​​of the detector units 14a are collected by the current information collecting circuit 16, the bed control circuit 17 determines whether or not there is a detector unit 14a whose current value exceeds a specified value (step S2).

[0061] Then, if there is a detector unit 14a whose current value exceeds a specified value (step S2, Yes), the bed control circuit 17 calculates the movement direction and movement amount of the tabletop 11 based on the position and current value of each detector unit 14a (step S3).

[0062] Thereafter, the bed control circuitry 17 calculates the position of the tabletop 11 after the movement based on the derived movement direction and movement amount, and stores position information indicating the calculated position in the memory 23 (step S4).

[0063] Then, the bed control circuitry 17 moves the tabletop 11 on which the subject P is placed, based on the derived direction and amount of movement (step S5).

[0064] Here, for example, the process of step S1 is realized by the current information collecting circuit 16 reading out from the memory 23 a program corresponding to the processing function of step S1 and executing it. Also, for example, the processes of steps S2 to S5 are realized by the bed control circuit 17 reading out from the memory 23 a program corresponding to the processing function of steps S2 to S5 and executing it.

[0065] As described above, in the first embodiment, the current information collecting circuit 16 collects current information indicating a current flowing through each detector unit 14a due to gamma rays emitted when the subject P is placed at the first position. In addition, the bed control circuit 17 controls the position of the tabletop 11 based on the current information collected by the current information collecting circuit 16, thereby moving the subject P from the first position to the second position.

[0066] According to this configuration, the position of the subject P can be optimized based on the distribution of currents in the multiple detector units 14a so that gamma rays are not concentrated in a specific detector unit 14a. Therefore, according to the first embodiment, it is possible to prevent an overcurrent in the detector unit 14a.

[0067] Furthermore, according to the first embodiment, by reconstructing a PET image taking into account the position information of the tabletop 11, the quantitativeness of the PET image can be improved compared to a method in which the current is limited by lowering the gain.

[0068] Furthermore, according to the first embodiment, by controlling the position of the tabletop 11 by actually measuring the current consumption of each detector unit 14a, control without delay is possible compared to control using event-based parameters such as count rate.

[0069] In the above description, the case where Rb-82 is used as the RI has been taken as an example, but this embodiment is not limited to Rb-82 and can be similarly applied to the case where other nuclides that have a risk of overcurrent due to high doses are used as the RI.

[0070] Although the first embodiment has been described above, the configuration of the above-mentioned PET device 100 can be implemented by modifying a part of it appropriately. Therefore, the following describes modifications of the first embodiment as other embodiments. Note that the following embodiments will mainly describe the points different from the first embodiment, and detailed description of points overlapping with the contents already described will be omitted.

[0071] Second Embodiment For example, in the first embodiment, an example has been described in which current information is collected by actually measuring the current flowing through each detector unit 14a after an RI is administered to the subject P, but the embodiment is not limited to this. For example, in a second embodiment, current information may be collected by estimating the current flowing through each detector unit 14a due to gamma rays emitted when the subject P is placed at the first position before an RI is administered to the subject P.

[0072] In this case, for example, before an RI is administered to the subject P, the current information collection circuit 16 collects current information by estimating the current flowing in each detector unit 14a due to gamma rays emitted when the subject P is placed at the first position based on information about the subject P and information about the RI.

[0073] Specifically, before data collection of the subject P, the current information collecting circuit 16 collects information on a current flowing through each detector unit 14a due to gamma rays emitted when the subject P is placed at an initial position within the opening of the gantry 10. Here, for example, the initial position is the center position within the opening of the gantry 10.

[0074] For example, the current information collecting circuit 16 uses machine learning to estimate the current flowing through each detector unit 14a due to gamma rays emitted when the subject P is placed at an initial position within the opening of the gantry device 10.

[0075] 6 and 7 are diagrams showing an example of current estimation performed by the current information collecting circuit 16 according to the second embodiment.

[0076] 6, the current information collecting circuit 16 uses a trained model that receives as input a CT image of the subject collected for attenuation correction and the dose of RI administered to the subject, and is trained to output a current that flows through each detector unit 14a when the subject is placed at an initial position in the opening of the gantry 10. The current information collecting circuit 16 then inputs a CT image of the subject P to be imaged and the dose of RI administered to the subject P to the trained model, thereby estimating a current that flows through each detector unit 14a when the subject P is placed at an initial position in the opening of the gantry 10.

[0077] 7, for example, the trained model is constructed by performing machine learning for a large number of subjects using, as training data, CT images of the subjects, the doses of RI administered to the subjects, and the currents flowing through each detector unit 14a when the subjects are placed at their initial positions in the opening of the gantry device 10. The trained model is constructed in advance before imaging of the subject P and stored in the memory 23.

[0078] Here, various machine learning techniques can be used, such as deep learning, logistic regression analysis, nonlinear discriminant analysis, support vector machine (SVM), random forest, and naive Bayes.

[0079] Although the example of estimating the current flowing through each detector unit 14a using machine learning has been described here, the method of estimating the current is not limited to this. For example, the current information collecting circuit 16 may estimate the current flowing through each detector unit 14a using Monte Carlo simulation, a mathematical model, or the like.

[0080] (Third embodiment) In addition, for example, in the first embodiment, an example is described in which the position of the subject P is optimized before data collection of the subject P is performed, but the embodiment is not limited to this. For example, in a third embodiment, the position of the subject P may be optimized while data collection of the subject P is being performed.

[0081] In this case, for example, the current information collecting circuit 16 collects current information by actually measuring the current flowing through each detector unit 14a at a predetermined timing while data is being collected from the subject P. Here, for example, the current information collecting circuit 16 may collect current information periodically at a predetermined time interval after imaging of the subject P is started, or may collect current information in response to an instruction from an operator.

[0082] For example, when current information is collected by the current information collection circuit 16, the bed control circuit 17 controls the position of the top board 11 based on the collected current information, thereby moving the subject P from the position where the top board 11 is positioned at that time to a position where the current distribution in the multiple detector units 14a is approximately uniform.

[0083] This embodiment may be implemented alone or in combination with the first or second embodiment. For example, before data collection of the subject P, the position of the subject P may be optimized using the method of the first or second embodiment, and while data collection of the subject P is being performed, the position of the subject P may be further optimized using the method of this embodiment. This makes it possible to more reliably prevent overcurrent in the detector unit 14a, for example, even when the conditions of the subject P or RI change before and after imaging is started due to some influence.

[0084] (Fourth embodiment) Also, for example, in the first or second embodiment, the position of the subject P may be optimized before data collection of the subject P is performed, and then the subject P may be moved to the initial position or the optimal position when the distribution of current flowing through each detector unit 14a becomes smaller than a predetermined value while data collection of the subject P is being performed.

[0085] In this case, for example, the current information collecting circuit 16 periodically collects current information at a predetermined time interval while data collection of the subject P is being performed.

[0086] Then, for example, after moving the subject P, the bed control circuit 17 returns the subject P to the initial position within the opening of the gantry device 10 when the current flowing through each detector unit 14a becomes smaller than a predetermined value.

[0087] Alternatively, for example, if the current flowing through each detector unit 14a becomes lower than a predetermined value after moving the subject P, the bed control circuit 17 further moves the subject P so that the distribution of the current flowing through the multiple detector units 14a becomes closer to uniform.

[0088] For example, when the subject P is moved by the above-mentioned method, the subject P may be unevenly positioned in the space within the opening, which may result in a decrease in the spatial resolution of the PET image. On the other hand, the RI administered to the subject P is excreted over time due to metabolism, etc., so that the gamma rays detected by the detector unit 14a also decrease over time. In this embodiment, the subject P is moved to the initial position or an optimal position at the point in time when the overcurrent of the detector unit 14a is avoided due to the decrease in gamma rays over time, thereby improving the spatial resolution of the PET image.

[0089] Fifth embodiment In the above-described embodiment, the subject P is moved in a direction along a plane perpendicular to the Z axis, but the embodiment is not limited to this. For example, the subject P may be moved in a direction along the Z axis in addition to a direction along a plane perpendicular to the Z axis.

[0090] In this case, for example, the current information collecting circuit 16 collects current information for each detector module 14b arranged in the Z-axis direction for each detector unit 14a.

[0091] Then, for example, the bed control circuitry 17 further moves the subject P in the Z-axis direction based on the current information for each detector module 14b collected by the current information collecting circuitry 16.

[0092] For example, the bed control circuitry 17 moves the subject P so that the current distribution in the Z direction approaches a uniform state based on the current information for each detector module 14b. For example, when a PET examination of the heart is performed, the bed control circuitry 17 moves the subject P so that the heart is positioned on a plane passing through the center of each of the multiple detector units 14a in the Z direction.

[0093] (Other embodiments) In the above embodiment, the gantry device 10 includes the current information collecting circuit 16 and the bed control circuit 17, but the embodiment is not limited to this. For example, the processing circuit 24 of the console device 20 may be configured to have the processing function of both or one of the current information collecting circuit 16 and the bed control circuit 17.

[0094] In the above-described embodiment, the bed control circuit 17 controls the position of the top board 11 by operating the bed driving mechanism 13 provided inside the bed 12, but the embodiment is not limited to this. For example, if the top board 11 is fixed to the bed 12 and the bed 12 itself is configured to be movable in the X-axis direction, the Y-axis direction, and the Z-axis direction, the bed control circuit 17 may control the position of the top board 11 by controlling the bed 12.

[0095] In addition, in the above-mentioned embodiment, the PET device has been described as an example of a nuclear medicine diagnosis device, but the embodiment is not limited thereto. For example, the technology disclosed in the present application can be similarly applied to other nuclear medicine diagnosis devices such as a SPECT (Single Photon Emission Computed Tomography) device.

[0096] In the above-described embodiment, the processing circuit is not limited to being realized by a single processor, but may be configured by combining multiple independent processors, and each processor may execute a program to realize each processing function. Each processing function of the processing circuit may be appropriately distributed or integrated into a single or multiple processing circuits. Each processing function of the processing circuit may be realized by a mixture of hardware such as a circuit and software. Here, an example in which a program corresponding to each processing function is stored in a single memory has been described, but the embodiment is not limited to this. For example, a configuration in which a program corresponding to each processing function is distributed and stored in multiple memories, and a processing circuit reads out and executes each program from each memory, may be used.

[0097] In the above-described embodiment, the collecting unit, the control unit, and the reconstructing unit in this specification are respectively realized by the current information collecting circuit 16, the bed control circuit 17, and the reconstruction function 24b of the processing circuit 24, but the embodiment is not limited to this. For example, the collecting unit, the control unit, and the reconstructing unit in this specification may be realized by only hardware, only software, or a combination of hardware and software, in addition to being realized by the current information collecting circuit 16, the bed control circuit 17, and the reconstruction function 24b of the processing circuit 24 described in the embodiment.

[0098] The term "processor" used in the description of the above-mentioned embodiment means a circuit such as a central processing unit (CPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA)). Here, instead of storing a program in a memory, the program may be directly embedded in the circuit of the processor. In this case, the processor realizes its function by reading and executing the program embedded in the circuit. Furthermore, each processor in the present embodiment is not limited to being configured as a single circuit for each processor, and may be configured as a single processor by combining multiple independent circuits to realize its function.

[0099] Here, the program executed by the processor is provided in advance in a ROM (Read Only Memory) or the like. The program may be provided by being recorded in a computer-readable non-transitory storage medium such as a CD (Compact Disk)-ROM, a FD (Flexible Disk), a CD-R (Recordable), or a DVD (Digital Versatile Disk) in a format that can be installed in these devices or in a format that can be executed. The program may also be provided or distributed by being stored on a computer connected to a network such as the Internet and downloaded via the network. For example, the program is composed of modules including each of the above-mentioned processing functions. As actual hardware, a CPU reads out the program from a storage medium such as a ROM and executes it, so that each module is loaded onto a main storage device and generated on the main storage device.

[0100] In the above-described embodiment, each component of each device shown in the figure is a functional concept, and does not necessarily have to be physically configured as shown in the figure. In other words, the specific form of distribution or integration of each device is not limited to that shown in the figure, and all or a part of it can be functionally or physically distributed or integrated in any unit according to various loads, usage conditions, etc. Furthermore, all or any part of each processing function performed by each device can be realized by a CPU and a program analyzed and executed by the CPU, or can be realized as hardware using wired logic.

[0101] Furthermore, among the processes described in the above-mentioned embodiments, all or part of the processes described as being performed automatically can be performed manually, or all or part of the processes described as being performed manually can be performed automatically by a known method. In addition, the information including the processing procedures, control procedures, specific names, various data and parameters shown in the above documents and drawings can be changed arbitrarily unless otherwise specified.

[0102] According to at least one of the embodiments described above, it is possible to prevent an overcurrent in the detector unit.

[0103] Although some embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations of embodiments can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0104] 100 PET equipment 10 Mounting device 16 Current information collection circuit 17 Bed control circuit 14 PET detector 14a Detector unit 14b Detector module

Claims

1. a top plate on which a subject administered with a radioisotope is placed; a plurality of detector units for detecting gamma rays emitted from the subject by the radioisotope; an acquisition unit that collects current information indicating a current flowing through each detector unit due to gamma rays emitted when the subject is placed at a first position; a control unit that controls a position of the tabletop based on the current information to move the subject from the first position to the second position; Equipped with The control unit controls a position of the top plate based on the current information, thereby moving the subject so that the distribution of the current in the multiple detector units approaches a uniform state.

2. the collecting unit collects the current information by actually measuring a current flowing through each detector unit due to gamma rays emitted from the subject placed at the first position after the radioisotope is administered to the subject; The nuclear medicine diagnostic apparatus according to claim 1 .

3. the collecting unit, before the radioisotope is administered to the subject, estimates a current flowing through each detector unit due to gamma rays emitted when the subject is placed at the first position, based on information about the subject and information about the radioisotope, to collect the current information; The nuclear medicine diagnostic apparatus according to claim 1 .

4. The collecting unit estimates the current using machine learning, Monte Carlo simulation, or a mathematical model. The nuclear medicine diagnostic apparatus according to claim 3.

5. the control unit returns the subject to the first position when a current flowing through each detector unit becomes smaller than a predetermined value after the subject is moved; The nuclear medicine diagnosis apparatus according to any one of claims 1 to 4.

6. when a current flowing through each detector unit becomes lower than a predetermined value after the control unit has moved the subject, the control unit further moves the subject so that a distribution of the current flowing through the plurality of detector units becomes closer to uniform. The nuclear medicine diagnosis apparatus according to any one of claims 1 to 4.

7. The plurality of detector units are arranged along a circumferential direction around a predetermined axis, The control unit moves the subject in a direction along a plane perpendicular to the axis. The nuclear medicine diagnosis apparatus according to any one of claims 1 to 6.

8. Each of the plurality of detector units includes a plurality of detector modules arranged in a direction along the axis, The collection unit collects the current information for each detector module for each detector unit; the control unit further moves the subject in a direction along the axis based on the current information collected for each of the detector modules. The nuclear medicine diagnostic apparatus according to claim 7.

9. A reconstruction unit that generates a PET image based on the gamma rays detected by the plurality of detector units, The control unit stores position information indicating a position of the tabletop after the subject is moved, the reconstruction unit reconstructs the PET image based on the gamma rays detected by the plurality of detector units after the subject is moved, taking into account position information of the top plate. The nuclear medicine diagnosis apparatus according to any one of claims 1 to 8.

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