PET-CT device and medical image processing method

Abstract

To improve image quality for a PET image obtaining by using a CT image for attenuation correction.SOLUTION: A PET-CT apparatus according to this embodiment includes a first acquisition unit, a first identification unit, a second acquisition unit, a gate processing unit and a reconfiguration processing unit. The first acquisition unit acquires a CT image for attenuation correction by scanning a subject. The first identification unit identifies an aspiration phase of the subject when the CT image is scanned. The second acquisition unit acquires PET scan data based on a gamma ray emitted from the subject. The gate processing unit generates gate data by gating the PET scan data on the basis of the aspiration phase. The reconfiguration processing unit reconfigures a PET image on the basis of the CT image and the gate data.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The embodiments disclosed in this specification and the drawings relate to a PET-CT apparatus, a medical image processing method, and a medical image processing program. [Background technology]

[0002] Conventionally, X-ray diagnostic devices such as PET (Positron Emission Tomography) devices and CT (Computed Tomography) devices have been used. Also, there exists an X-ray diagnostic device that is integrally equipped with a PET device and a CT device (hereinafter, PET-CT device). In such a PET-CT device, when a PET image is generated by reconstructing PET raw data acquired by the PET device, the PET raw data is corrected (hereinafter, attenuation correction) using attenuation correction data (e.g., attenuation map) generated based on the CT image.

[0003] In imaging using a PET apparatus, imaging is performed while the subject is breathing. However, since artifacts occur due to bodily movements associated with breathing, scanning is performed in synchronization with the subject's breathing.

[0004] However, in the above-mentioned PET-CT device, when a CT image is used for attenuation correction, no particular consideration is given to synchronization with the respiratory phase of the PET raw data. Therefore, in the conventional PET-CT device, there is a possibility that attenuation correction is performed using a CT image taken in a respiratory phase different from the respiratory phase when the PET raw data is acquired. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-189362 A DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0006] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to provide a PET-CT device, a medical image processing method, and a medical image processing program that can improve the image quality of a PET image using a CT image for attenuation correction. 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]

[0007] The PET-CT device according to the embodiment includes a first acquisition unit, a first identification unit, a second acquisition unit, a gate processing unit, and a reconstruction processing unit. The first acquisition unit acquires a CT image for attenuation correction by scanning a subject. The first identification unit identifies the respiratory phase of the subject when the CT image is scanned. The second acquisition unit acquires PET scan data based on gamma rays emitted from the subject. The gate processing unit generates gate data by gating the PET scan data based on the respiratory phase. The reconstruction processing unit reconstructs a PET image based on the CT image and the gate data. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the configuration of a PET-CT apparatus according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of the arrangement positions of infrared cameras relative to a CT gantry and a PET gantry according to the embodiment. [Diagram 3] FIG. 3 is a sequence diagram showing an example of a scan operation performed by the PET-CT apparatus of the embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a CT respiratory waveform according to the embodiment. [Diagram 5] FIG. 5 is a diagram showing an example of a PET respiratory waveform according to an embodiment. [Figure 6]FIG. 6 is a flowchart showing an example of a scan process performed by the processing circuitry of the PET-CT apparatus of the embodiment. BEST MODE FOR CARRYING OUT THEINVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the PET-CT apparatus, medical image processing method, and medical image processing program according to the present invention will be described with reference to the accompanying drawings.

[0010] Fig. 1 is a diagram showing the configuration of a PET-CT device 1 according to this embodiment. As shown in Fig. 1, the PET-CT device 1 has a PET gantry 10, a CT gantry 30, a bed 50, an infrared camera 60, and a console 70. Typically, the PET gantry 10, the CT gantry 30, the bed 50, and the infrared camera 60 are installed in a common examination room. The console 70 is installed in a control room adjacent to the examination room.

[0011] The PET gantry 10 is an imaging device for performing a PET scan on the subject P. The CT gantry 30 is an imaging device for performing a CT scan on the subject P. The bed 50 movably supports a top board 53 on which the subject P to be imaged is placed. The console 70 is a computer that controls the PET gantry 10, the CT gantry 30, the bed 50, and the like.

[0012] The PET gantry 10 has, for example, a plurality of PET detector rings, a signal processing circuit 13, a coincidence circuit 15, and a ring moving mechanism 16. Although one PET detector ring 11 is shown in FIG. 1, the actual PET gantry 10 is equipped with a plurality of PET detector rings that are movable relative to a top plate 53 along the central axis direction (Z direction) of a bore 20 into which a top plate 53 on which a subject P is placed is inserted. The signal processing circuit 13 and the coincidence circuit 15 are provided for, for example, each of the plurality of PET detector rings. The ring moving mechanism 16 supports each of the plurality of PET detector rings so that they can be moved along the central axis direction (Z direction) of the bore 20. The PET gantry 10 and the CT gantry 30 may be housed in the same housing.

[0013] The PET detector ring 11 has a plurality of gamma ray detectors 17 arranged on a circumference around the central axis Z. The gamma ray detectors 17 are also called PET detectors. An image field of view (FOV) is set at the opening of the PET detector ring 11. The subject P is positioned so that the imaging site of the subject P is included in the image field of view. A drug labeled with a positron-emitting nuclide is administered to the subject P. Positrons emitted from the positron-emitting nuclide annihilate with surrounding electrons. A pair of pair annihilation gamma rays is generated by the annihilation. The gamma ray detector 17 detects pair annihilation gamma rays emitted from the body of the subject P. The gamma ray detector 17 generates an electric signal according to the light amount of the detected pair annihilation gamma rays. For example, the gamma ray detector 17 has a plurality of scintillators and a plurality of photomultiplier tubes. The scintillator receives pair annihilation gamma rays originating from a radioisotope in the subject P and generates scintillation light. The photomultiplier tube generates an electric signal according to the amount of scintillation light. The generated electric signal is supplied to a signal processing circuit 13.

[0014] The signal processing circuit 13 generates single event data based on the electrical signal output from the gamma ray detector 17. Specifically, the signal processing circuit 13 performs, for example, detection time measurement processing, position calculation processing, and energy calculation processing on the electrical signal. The signal processing circuit 13 is realized by an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), another Complex Programmable Logic Device (CPLD), or a Simple Programmable Logic Device (SPLD) configured to be able to execute the detection time measurement processing, position calculation processing, and energy calculation processing.

[0015] In the detection time measurement process, the signal processing circuit 13 measures the time when the gamma ray is detected by the gamma ray detector 17. Specifically, the signal processing circuit 13 monitors the peak value of the electrical signal from the gamma ray detector 17, and measures the time when the peak value exceeds a preset threshold as the detection time. In other words, the signal processing circuit 13 detects that the peak value has exceeded the threshold, thereby electrically detecting pair-annihilation gamma rays. In the position calculation process, the signal processing circuit 13 calculates the incident position of the pair-annihilation gamma ray based on the electrical signal from the gamma ray detector 17. The incident position of the pair-annihilation gamma ray corresponds to the position coordinates of the scintillator into which the pair-annihilation gamma ray is incident. In the energy calculation process, the signal processing circuit 13 calculates the energy value of the detected pair-annihilation gamma ray based on the electrical signal from the gamma ray detector 17.

[0016] The detection time data, position coordinate data, and energy value data for a single event are associated with each other. The combination of the energy value data, position coordinate data, and detection time data for a single event is called single event data. Single event data is generated one after another every time an annihilation gamma ray is detected. The generated single event data is supplied to the coincidence counting circuit 15.

[0017] The coincidence circuit 15 performs coincidence processing on the single event data from the signal processing circuit 13. As hardware resources, the coincidence circuit 15 is realized by an ASIC, FPGA, CPLD, or SPLD configured to be able to execute coincidence processing. In the coincidence processing, the coincidence circuit 15 repeatedly identifies single event data related to two single events that fall within a predetermined time frame from the repeatedly supplied single event data. This pair of single events is presumed to be derived from pair annihilation gamma rays generated from the same pair annihilation point. The pair of single events are collectively called coincidence events. A line connecting the pair of gamma ray detectors 17 (more specifically, scintillators) that detected this pair annihilation gamma ray is called an LOR (Line Of Response). Event data related to the pair of events that constitute the LOR is called coincidence event data. The coincidence event data and single event data are transmitted to a console 70. The coincidence event data is also used when reconstructing a PET image. Hereinafter, the coincidence event data is also called PET raw data. It should be noted that PET raw data is an example of PET scan data.

[0018] In the above configuration, the signal processing circuit 13 and the coincidence circuit 15 are included in the PET gantry 10, but this embodiment is not limited to this. For example, the coincidence circuit 15, or both the signal processing circuit 13 and the coincidence circuit 15, may be included in a device separate from the PET gantry 10. Also, one coincidence circuit 15 may be provided for the multiple signal processing circuits 13 mounted on the PET gantry 10, or the multiple signal processing circuits 13 mounted on the PET gantry 10 may be divided into multiple groups and one coincidence circuit 15 may be provided for each group.

[0019] The ring moving mechanism 16 moves the multiple PET detector rings along the central axis direction (Z direction) of the bore 20 under the control of an imaging control function 733 in the processing circuit 73 described later. The ring moving mechanism 16 has, for example, a ring support mechanism that supports the multiple PET detector rings movably along the central axis direction (Z direction) of the bore 20, a moving mechanism that moves the multiple PET detector rings in the ring support mechanism, and a driving mechanism that drives the moving part. The ring support mechanism is realized, for example, by a linear bearing arranged in the PET gantry 10 along the central axis direction (Z direction) of the bore 20. The means for realizing the ring support mechanism is not limited to a linear bearing, and various known bearings and the like can be appropriately used. The rails of the linear bearing are provided on a fixed frame in the PET gantry 10 along the central axis direction (Z direction) of the bore 20. In addition, in the linear bearing, a block that runs on the rail carries a support frame that keeps each of the multiple PET detector rings in a ring shape.

[0020] The moving mechanism is realized by a plurality of racks and pinions corresponding to the plurality of PET detector rings. The means for realizing the moving mechanism is not limited to the rack and pinion, and a known device such as a ball screw can be appropriately used. The plurality of rack gears in the plurality of racks and pinions are arranged along the central axis direction (Z direction) of the bore 20, and are respectively connected to a plurality of holding frames corresponding to the plurality of PET detector rings. The plurality of pinion gears are respectively fitted into the plurality of rack gears. The pinion gear may be provided with, for example, a rotary encoder that measures the number of rotations of the pinion gear. At this time, the output from the rotary encoder is output to the processing circuit 73.

[0021] The drive mechanism is realized by, for example, a motor. The rotating shaft of the motor is connected to the pinion gear via, for example, various gears. If the pinion gear is not provided with a rotary encoder, the rotating shaft of the motor or the various gears may be provided with, for example, a rotary encoder for measuring the number of rotations of the rotating shaft. At this time, the output from the rotary encoder is output to the processing circuit 73. The motor is driven according to a control signal from the imaging control function 733. The pinion gear is rotated by the rotation of the motor, and the rack gear moves along the central axis direction (Z direction) of the bore 20. The movement of the rack gear moves the multiple PET detector rings along the central axis direction (Z direction) of the bore 20.

[0022] 1, the CT gantry 30 has a CT imaging mechanism. The CT imaging mechanism performs a CT scan on a subject P. The CT imaging mechanism may also perform X-ray scanography on the subject P. The CT imaging mechanism has an X-ray tube 31, an X-ray detector 32, a rotating frame 33, an X-ray high voltage device 34, a CT control device 35, a wedge 36, a collimator 37, and a DAS 38.

[0023] The X-ray tube 31 generates X-rays. Specifically, the X-ray tube 31 has a vacuum tube that holds a cathode that generates thermoelectrons and an anode that receives thermoelectrons flying from the cathode and generates X-rays. The X-ray tube 31 is connected to the X-ray high voltage device 34 via a high-voltage cable. A tube voltage is applied between the cathode and the anode by the X-ray high voltage device 34. The application of the tube voltage causes thermoelectrons to fly from the cathode to the anode. The thermoelectrons flying from the cathode to the anode cause a tube current to flow. The application of a high voltage from the X-ray high voltage device 34 and the supply of a filament current cause thermoelectrons to fly from the cathode to the anode, and the thermoelectrons collide with the anode. This generates X-rays.

[0024] The X-ray detector 32 detects X-rays generated from the X-ray tube 31 and passing through the subject P. The X-ray detector 32 outputs an electric signal corresponding to the dose of the detected X-rays to the DAS 38. The X-ray detector 32 has a structure in which a plurality of X-ray detection element rows, each of which has a plurality of X-ray detection elements arranged in the channel direction, are arranged in the slice direction (also called the row direction). The X-ray detector 32 is, for example, an indirect conversion type detector having a grid, a scintillator array, and an optical sensor array. The scintillator array has a plurality of scintillators. The scintillator outputs light with an amount of light corresponding to the amount of incident X-rays. The grid is arranged on the X-ray incidence surface side of the scintillator array. The grid has an X-ray shielding plate that absorbs scattered X-rays. The optical sensor array converts the light output from the scintillator into an electric signal corresponding to the amount of light. For example, a photodiode or a photomultiplier tube is used as the optical sensor. The X-ray detector 32 may be realized by a direct conversion type detector (semiconductor detector) having a semiconductor element that converts incident X-rays into an electrical signal.

[0025] The rotating frame 33 is an annular frame that supports the X-ray tube 31 and the X-ray detector 32 rotatably around a rotation axis Z. Specifically, the rotating frame 33 supports the X-ray tube 31 and the X-ray detector 32 facing each other. The rotating frame 33 is supported by a fixed frame (not shown) so as to be rotatable around the rotation axis Z. The rotating frame 33 rotates around the rotation axis Z under the control of the CT control device 35. As a result, the X-ray tube 31 and the X-ray detector 32 rotate around the rotation axis Z. The rotating frame 33 receives power from a drive mechanism of the CT control device 35 and rotates around the rotation axis Z at a constant angular velocity. An image field of view (FOV) is set at an opening of the rotating frame 33.

[0026] In this embodiment, the rotation axis of the rotating frame 33 in the non-tilted state or the longitudinal direction of the top board 53 of the bed 50 is defined as the Z-axis direction, the axial direction perpendicular to the Z-axis direction and horizontal to the floor surface is defined as the X-axis direction, and the axial direction perpendicular to the Z-axis direction and perpendicular to the floor surface is defined as the Y-axis direction.

[0027] The X-ray high voltage device 34 has electric circuits such as a transformer and a rectifier. The X-ray high voltage device 34 also has a high voltage generator that generates a high voltage to be applied to the X-ray tube 31 and a filament current to be supplied to the X-ray tube 31, and an X-ray control device that controls an output voltage according to the X-rays irradiated by the X-ray tube 31. The high voltage generator may be of a transformer type or an inverter type. The X-ray high voltage device 34 may be provided on the rotating frame 33 in the CT gantry 30, or on a fixed frame (not shown) in the CT gantry 30.

[0028] The wedge 36 adjusts the dose of X-rays irradiated to the subject P. Specifically, the wedge 36 attenuates the X-rays so that the dose of X-rays irradiated from the X-ray tube 31 to the subject P has a predetermined distribution. For example, the wedge 36 is a metal plate such as aluminum, such as a wedge filter or a bow-tie filter.

[0029] The collimator 37 limits the irradiation range of the X-rays transmitted through the wedge 36. The collimator 37 slidably supports a plurality of lead plates that block X-rays, and adjusts the shape of the slits formed by the plurality of lead plates.

[0030] A DAS (Data Acquisition System) 38 reads out an electrical signal corresponding to the X-ray dose detected by the X-ray detector 32 from the X-ray detector 32. The DAS 38 amplifies the read out electrical signal with a variable amplification factor. The DAS 38 then integrates the amplified electrical signal over a view period to collect CT raw data (e.g., a sinogram) having digital values ​​corresponding to the X-ray dose over the view period. The DAS 38 is realized, for example, by an ASIC equipped with circuit elements capable of generating CT raw data. The CT raw data is transmitted to the console 70 via a non-contact data transmission device or the like.

[0031] The CT control device 35 controls the X-ray high voltage device 34, the DAS 38, and the like to execute a CT scan using an imaging control function 733 of the processing circuit 73 of the console 70. The CT control device 35 has a processing circuit having a CPU (Central Processing Unit) and the like, and a driving mechanism such as a motor and an actuator. The processing circuit has, as hardware resources, a processor such as a CPU or an MPU (Micro-Processing Unit) and a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory). The CT control device 35 may also be realized by an ASIC, an FPGA, a CPLD, a SPLD, or the like.

[0032] The CT gantry 30 is available in various types, such as a Rotate / Rotate-Type (third generation CT) in which the X-ray generating unit and the X-ray detecting unit rotate around the subject as a unit, and a Stationary / Rotate-Type (fourth generation CT) in which a large number of X-ray detecting elements are fixed in a ring-shaped array and only the X-ray generating unit rotates around the subject, and any of these types can be applied to one embodiment.

[0033] 1, a subject P to be scanned is placed on a bed 50, and the subject is moved. The bed 50 is shared by the PET gantry 10 and the CT gantry 30.

[0034] The bed 50 includes a base 51, a support frame 52, a top plate 53, and a bed driving device 54. The base 51 is placed on the floor surface. The base 51 is a housing that supports the support frame 52 so that it can move vertically (in the Y-axis direction) relative to the floor surface. The support frame 52 is a frame provided on the upper part of the base 51. The support frame 52 supports the top plate 53 so that it can slide along the central axis Z. The top plate 53 is a flexible plate on which the subject P is placed.

[0035] The bed driving device 54 is housed in the housing of the bed 50. The bed driving device 54 is a motor or actuator that generates power for moving the support frame 52 on which the subject P is placed and the tabletop 53. The bed driving device 54 operates under the control of the console 70 or the like.

[0036] The PET gantry 10 and the CT gantry 30 are disposed so that the central axis Z of the opening of the PET gantry 10 and the central axis Z of the opening of the CT gantry 30 approximately coincide with each other. The bed 50 is disposed so that the long axis of the tabletop 53 is parallel to the central axis Z of the openings of the PET gantry 10 and the CT gantry 30. The CT gantry 30 and the PET gantry 10 are installed in this order, for example, from the side closer to the bed 50. In the following, an example will be described in which a CT scan is performed with the CT gantry 30 and then a PET scan is performed with the PET gantry 10, but the order of performing the CT scan and the PET scan may be reversed.

[0037] 1, the infrared camera 60 is provided at a position where it can capture an image of a subject P placed on a bed 50. The infrared camera 60 has an infrared imaging element and the like, and generates and outputs data that visualizes infrared rays emitted from an object. Here, the infrared camera 60 is an example of a monitoring device that monitors the subject P.

[0038] Specifically, as shown in Fig. 2, the infrared camera 60 is provided at a position and angle that allows it to capture an image of the upper surface of the tabletop 53 inserted into the bore 20. Here, Fig. 2 is a diagram showing an example of the arrangement position of the infrared camera 60 relative to the CT gantry 30 and the PET gantry 10.

[0039] 2, an infrared camera 60 captures images of parts of a subject P whose shape and temperature change with breathing, such as the chest and abdomen, of the subject P placed on a tabletop 53. The data captured by the infrared camera 60 is used to derive a respiratory waveform of the subject P.

[0040] In this way, by using the infrared camera 60, even if the examination room is dark, for example, it is possible to derive a respiratory waveform from the data output by the infrared camera 60. Also, by using the infrared camera 60, even if the subject P is covered with a drape or the like, it is possible to derive a respiratory waveform from the data output by the infrared camera 60. Therefore, by using the infrared camera 60, it is possible to improve convenience.

[0041] 1 and 2 show an example in which the infrared camera 60 is provided outside the CT gantry 30 and the PET gantry 10, but the present invention is not limited to this. For example, the infrared camera 60 may be provided around the opening of the CT gantry 30 or the PET gantry 10, or inside the bore 20.

[0042] 1, the console 70 includes a PET data memory 71, a CT data memory 72, a processing circuit 73, a display 74, a memory 75, and an input interface 76. For example, data communication between the PET data memory 71, the CT data memory 72, the processing circuit 73, the display 74, the memory 75, and the input interface 76 is performed via a bus.

[0043] The PET data memory 71 is a storage device that stores the single event data and coincidence event data transmitted from the PET gantry 10. The PET data memory 71 is a storage device such as a hard disk drive (HDD), a solid state drive (SSD), or an integrated circuit storage device.

[0044] The CT data memory 72 is a storage device that stores the CT raw data transmitted from the CT gantry 30. The CT data memory 72 is a storage device such as an HDD, an SSD, or an integrated circuit storage device.

[0045] The processing circuitry 73 has a processor such as a CPU, an MPU, a GPU (Graphics Processing Unit), and a memory such as a ROM or a RAM as hardware resources. The processing circuitry 73 executes various programs read from the memory to realize a monitor control function 731, a respiratory waveform acquisition function 732, an imaging control function 733, a reconstruction function 734, an image processing function 735, and a display control function 736. That is, the processing circuitry 73 corresponds to a processor that reads a program from the memory and executes it to realize a function corresponding to each program. In other words, the processing circuitry 73 in a state where each program has been read has a function corresponding to the read program.

[0046] The monitor control function 731, the respiratory waveform acquisition function 732, the imaging control function 733, the reconstruction function 734, the image processing function 735, and the display control function 736 may be implemented by the processing circuit 73 of one board, or may be distributed and implemented by the processing circuits 73 of multiple boards. The processing circuit 73 that realizes the monitor control function 731, the respiratory waveform acquisition function 732, the imaging control function 733, the reconstruction function 734, the image processing function 735, and the display control function 736 corresponds to the first acquisition unit, the first identification unit, the second acquisition unit, the gate processing unit, the reconstruction processing unit, and the third acquisition unit, respectively. More specifically, the first acquisition unit corresponds to the imaging control function 733 and the reconstruction function 734. The second acquisition unit, the gate processing unit, and the reconstruction processing unit correspond to the reconstruction function 734. The third acquisition unit corresponds to the respiratory waveform acquisition function 732.

[0047] In the monitor control function 731, the processing circuitry 73 controls the operation of the infrared camera 60. Specifically, the processing circuitry 73 monitors the subject P by operating the infrared camera 60 in conjunction with the operation of the PET-CT device 1. For example, when the PET-CT device 1 starts imaging, the processing circuitry 73 starts monitoring the subject P by operating the infrared camera 60. Furthermore, when the scanning operation of the PET-CT device 1 ends, the processing circuitry 73 ends the monitoring of the subject P by stopping the infrared camera 60.

[0048] In addition, in the monitor control function 731, the processing circuitry 73 acquires data output by the infrared camera 60 and stores it in the memory 75 or the like as monitor data of the subject P. For example, the processing circuitry 73 separately stores the monitor data output by the infrared camera 60 during a CT scan and a PET scan. In addition, the processing circuitry 73 transfers the monitor data acquired in each of the CT scan and the PET scan to a respiratory waveform acquisition function 732.

[0049] In the respiratory waveform acquisition function 732, the processing circuitry 73 detects the respiratory dynamics of the subject P, such as exhalation and inhalation, from the monitor data acquired by the monitor control function 731, and acquires a respiratory waveform that represents the respiratory dynamics in a time series. Specifically, the processing circuitry 73 acquires the respiratory waveform of the subject P during the CT scan (hereinafter, CT respiratory waveform) from the monitor data acquired during the CT scan. The processing circuitry 73 also acquires the respiratory waveform of the subject P during the PET scan (hereinafter, PET respiratory waveform) from the monitor data acquired during the PET scan.

[0050] The method of detecting the respiratory behavior is not particularly limited, and existing detection methods such as respiratory monitoring technology using moving image processing can be used. For example, in the case of this embodiment, the monitoring data output by the infrared camera 60 represents the temperature difference between the human body region of the subject P and other regions other than the human body region. Therefore, the processing circuitry 73 may detect the respiratory behavior of the subject P based on the time-series image change (temperature change) of the boundary portion between the human body region and other regions. Also, for example, it is known that the temperature of the chest, abdomen, etc. changes with breathing. Therefore, the processing circuitry 73 may detect the respiratory behavior based on the time-series image change (temperature change) of the human body parts of the subject P represented in the monitoring data.

[0051] In addition, in the respiratory waveform acquisition function 732, the processing circuitry 73 cooperates with the imaging control function 733 described later to acquire the start time and end time of the CT scan and record them in association with the CT respiratory waveform. For example, the respiratory waveform acquisition function 732 records the start time and end time of the CT scan in association with the time axis of the CT respiratory waveform.

[0052] In the imaging control function 733, the processing circuitry 73 synchronously controls the CT gantry 30 and the bed 50 to perform a CT scan. The processing circuitry 73 also controls the CT scan by the CT gantry 30 by cooperating with the CT control device 35 and the like. The processing circuitry 73 also synchronously controls the PET gantry 10 and the bed 50 to perform a PET scan. The processing circuitry 73 also controls the PET scan by the PET gantry 10 by cooperating with the clock circuitry 15 and the like. When a CT scan and a PET scan are performed consecutively, the processing circuitry 73 synchronously controls the CT gantry 30, the PET gantry 10, and the bed 50. For example, the processing circuitry 73 performs a CT scan to obtain a CT image for attenuation correction to be used for attenuation correction of the PET image.

[0053] In the reconstruction function 734, the processing circuitry 73 reconstructs a CT image expressing the spatial distribution of CT values ​​related to the subject P based on the CT raw data obtained by the CT scan. The processing circuitry 73 also reconstructs a PET image showing the distribution of positron-emitting nuclides administered to the subject P based on the coincidence event data obtained by the PET scan. The processing circuitry 73 can also generate a CT-related positioning image (CT scanogram image) based on the CT raw data, and generate a PET-related positioning image based on the PET raw data.

[0054] In addition, in the reconstruction function 734, the processing circuitry 73 reconstructs an attenuation-corrected PET image based on the CT image for attenuation correction obtained by the CT scan and the PET raw data. Specifically, the processing circuitry 73 identifies the respiratory phase of the subject P when the CT scan was performed (hereinafter also referred to as the CT respiratory phase) based on the start time and end time of the CT scan recorded in association with the CT respiratory waveform.

[0055] The processing circuitry 73 also generates gating data by gating the PET raw data based on the identified CT respiratory phase. Specifically, the processing circuitry 73 generates gating data by extracting PET raw data acquired during a period corresponding to the CT respiratory phase based on the PET respiratory waveform during the PET scan. Then, the processing circuitry 73 reconstructs an attenuation-corrected PET image based on the CT image for attenuation correction obtained by the CT scan and the gating data.

[0056] In this way, the processing circuitry 73 extracts PET raw data (gate data) acquired at a respiratory phase substantially equal to the respiratory phase when the CT image is scanned, and reconstructs a PET image based on the CT image and the gate data. This allows the processing circuitry 73 to improve the synchronization accuracy of the respiratory phase between the CT image and the PET raw data, and therefore allows the acquisition of an attenuation-corrected PET image in which the influence of respiratory movement is suppressed.

[0057] As the image reconstruction algorithm, for example, an existing image reconstruction algorithm such as the Filtered Back Projection (FBP) method or the iterative reconstruction method may be used. As the gating method, for example, an existing technique such as the retrospective gating method or the prospective gating method may be used. As the attenuation correction method, for example, an existing technique such as CTAC (CT-based Attenuation Correction) that converts a CT image into an attenuation map (μ-map) and corrects it may be used.

[0058] In the image processing function 735, the processing circuitry 73 performs various image processing on the CT image and the PET image reconstructed by the reconstruction function 734. For example, the processing circuitry 73 performs three-dimensional image processing such as volume rendering, surface volume rendering, pixel value projection processing, MPR (Multi-Planer Reconstruction) processing, and CPR (Curved MPR) processing on the CT image and the PET image to generate a display image. Also, for example, the processing circuitry 73 generates a composite image by combining the PET image and the CT image.

[0059] In the display control function 736, the processing circuitry 73 generates various display information and displays the generated display information on the display 74. For example, the processing circuitry 73 generates the display information by associating the positions of the multiple PET detector rings 101 with information about the subject P. The display information is, for example, information indicating the relative positional relationship of the multiple PET detector rings 101 with respect to the subject P placed on the top board 53. At this time, the display information has ring display objects indicating each of the multiple PET detector rings as the positions of the multiple PET detector rings 101. Note that the display information may further have the position of the X-ray detector 32 with respect to the subject P.

[0060] In addition, the display information may further include information indicating the imaging range for the subject P (e.g., a dotted frame or an imaging mode indicating the area to be imaged, etc.) depending on the user's instructions via the input interface 76 or the examination area in the examination order output from the radiology information system (RIS) or hospital information system (HIS).

[0061] The display 74 displays various information under the control of a display control function 736 in the processing circuit 73. As the display 74, for example, a CRT (Cathode Ray Tube) display, a liquid crystal display (LCD), an organic electroluminescence display (OLED), a light emitting diode (LED) display, a plasma display, or any other display known in the art can be appropriately used. The display 74 may be a desktop type, or may be configured as a tablet terminal capable of wireless communication with the console 70. The display 74 corresponds to a display unit.

[0062] The memory 75 is a storage device such as an HDD, SSD, integrated circuit storage device, etc., that stores various information. The memory 75 may also be a drive device that reads and writes various information from and to a portable storage medium such as a CD (Compact Disc)-ROM drive, a DVD (Digital Versatile Disc) drive, or a flash memory.

[0063] The memory 75 stores, for example, various programs and various data related to the execution of the monitor control function 731, the respiratory waveform acquisition function 732, the imaging control function 733, the reconstruction function 734, the image processing function 735, the display control function 736, etc. The memory 75 also stores, for example, monitor data acquired by the monitor control function 731. The memory 75 also stores, for example, CT images and PET images reconstructed by the reconstruction function 734.

[0064] The input interface 76 accepts various input operations from the user (e.g., an instruction to execute a CT scan or a PET scan, a selection of an imaging range, etc.), converts the accepted input operations into electrical signals, and outputs the electrical signals to the processing circuitry 73. For example, as the input interface 76, for example, a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touchpad, a touch panel display, etc. can be appropriately used. Note that, in this embodiment, the input interface 76 is not limited to one having physical operation parts such as a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touchpad, and a touch panel display. For example, an example of the input interface 76 includes an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the device and outputs the electrical signal to the processing circuitry 73. The input interface 76 may also be configured as a tablet terminal or the like capable of wireless communication with the console 70. The input interface 76 corresponds to an input unit.

[0065] Above is a description of the overall configuration of the PET-CT device 1. Next, an example of the operation of the PET-CT device 1 will be described with reference to FIG.

[0066] Fig. 3 is a sequence diagram showing an example of a scan operation performed by the PET-CT device 1. Note that Fig. 3 describes a scan operation in which a CT image for attenuation correction is acquired and then a PET image is reconstructed using the CT image. In the following, the functions realized by the processing circuitry 73 will be described as the subject of the operation.

[0067] First, the imaging control function 733 starts a scan operation by the PET-CT device 1 in response to an operation instruction via the input interface 76 (step S11). In response to the start of the scan operation in step S11, the monitor control function 731 starts monitoring the subject P by the infrared camera 60 (step S21).

[0068] Next, the imaging control function 733 synchronously controls the CT gantry 30 and the bed 50 to start the CT scan (step S12). For example, an operator or technician of the PET-CT device 1 guides the breathing of the subject P when starting the CT scan, thereby starting the CT scan at a timing of a predetermined respiratory phase such as maximum expiration or maximum inspiration. At the timing of starting the CT scan, the imaging control function 733 notifies the respiratory waveform acquisition function 732 of the start time indicating the time when the CT scan was started.

[0069] When the imaging control function 733 finishes the CT scan (step S13), it moves the bed 50 to perform a PET scan (step S14). Furthermore, when the CT scan is finished, the imaging control function 733 notifies the respiratory waveform acquisition function 732 of the end time indicating the time when the CT scan is finished.

[0070] When the CT scan is completed, the monitor control function 731 transfers the monitor data acquired up to that point to the respiratory waveform acquisition function 732 (step S22). The respiratory waveform acquisition function 732 acquires the CT respiratory waveform from the monitor data transferred in step S22 (step S31). The respiratory waveform acquisition function 732 also records the start time and end time notified by the imaging control function 733 in the CT respiratory waveform.

[0071] The reconstruction function 734 identifies the CT respiratory phase when the CT scan was performed based on the CT respiratory waveform acquired in step S31. For example, when the CT scan is performed at the timing of exhalation, the reconstruction function 734 identifies the exhalation phase as the CT respiratory phase. Note that the timing for identifying the CT respiratory phase is not limited to this. For example, the reconstruction function 734 may identify the CT respiratory phase after the end of the PET scan.

[0072] Furthermore, when the CT scan is completed, the reconstruction function 734 reconstructs a CT image from the CT raw data obtained by the CT scan, thereby acquiring a CT image for attenuation correction (step S41).

[0073] After moving the bed 50 in step S14, the imaging control function 733 starts a PET scan (step S15). Then, when the PET scan ends (step S16), the imaging control function 733 ends the scan operation by the PET-CT device 1 (step S17).

[0074] When the PET scan is completed, the monitor control function 731 transfers the monitor data acquired up to that point to the respiratory waveform acquisition function 732 (step S23). Then, in conjunction with the completion of the scan in step S17, the monitor control function 731 ends the monitoring of the subject P by the infrared camera 60 (step S24).

[0075] The respiratory waveform acquisition function 732 acquires the PET respiratory waveform from the monitor data transferred in step S23 (step S32). Next, the reconstruction function 734 extracts gating data of the respiratory phase corresponding to the CT respiratory phase (hereinafter also referred to as the PET respiratory phase) from the PET raw data obtained by the PET scan based on the PET respiratory waveform during the PET scan (step S42).

[0076] Then, the reconstruction function 734 reconstructs an attenuation-corrected PET image based on the CT image for attenuation correction and the gating data (step S43), and ends the process (step S44).

[0077] Here, the process of step S42 described above will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a diagram showing an example of a CT respiratory waveform, and Fig. 5 is a diagram showing an example of a PET respiratory waveform.

[0078] As shown in Figures 4 and 5, the respiratory waveform is time-series waveform data that represents the respiratory dynamics of the subject P. The horizontal axis is the time axis, and the vertical axis is the amplitude of the respiratory motion. Note that an upward movement of the waveform indicates the dynamics of inspiration, and a downward movement of the waveform indicates the dynamics of expiration.

[0079] For example, in the CT respiratory waveform shown in Fig. 4, the execution time (from the start time to the end time) of the CT scan recorded in association with the CT respiratory waveform is assumed to be time T1. In this case, the reconstruction function 734 determines that the CT respiratory phase when the CT scan was performed is in the expiratory phase from the position of time T1 in the CT respiratory waveform. Next, the reconstruction function 734 determines the respiratory period P2 and the respiratory period P3 of the PET respiratory phase corresponding to the CT respiratory phase from the PET respiratory waveform shown in Fig. 5. Next, the reconstruction function 734 extracts the PET raw data obtained by the PET scan in the respiratory periods P2 and P3 as gating data from the PET raw data obtained by the PET scan when the PET respiratory waveform is acquired.

[0080] The respiratory phase of the gating data extracted in the above process is the same as the respiratory phase when the CT image is acquired. Therefore, the PET image generated in the subsequent step S43 is an attenuation-corrected PET image that suppresses the influence of respiratory movement. Therefore, the reconstruction function 734 can improve the image quality of the PET image using the CT image for attenuation correction.

[0081] The method of identifying the respiratory phase is not limited to the above example. For example, the reconstruction function 734 may identify the respiratory phase based on either the start time or the end time of the CT scan. As an example, when the time required for the CT scan is known in advance, the start time or the end time can be derived from the other time. Therefore, when the time required for the CT scan is known in advance, the reconstruction function 734 can identify the respiratory phase when the CT scan is performed from either the start time or the end time. In this case, the respiratory waveform acquisition function 732 may be configured to record either the start time or the end time of the CT scan.

[0082] The reconstruction function 734 may also identify the respiratory phase based on the depth and amount of change of the respiratory phase. For example, when the execution time of the CT scan is time T1, the reconstruction function 734 identifies the depth (amplitude value) of the respiratory phase at the time T1 and the amount of change in the direction of increase and decrease of the amplitude as the respiratory phase. Next, the reconstruction function 734 identifies the time T2 and the time T3 at which the PET respiratory phase corresponding to the depth and amount of change of the identified respiratory phase appears from the PET respiratory waveform shown in FIG. Next, the reconstruction function 734 sets a predetermined respiratory period (e.g., P2, P3) that is expanded before and after the reference, using the time T2 and the time T3 as the reference. Then, the reconstruction function 734 extracts gating data obtained by the PET scan during the set respiratory period.

[0083] This allows the reconstruction function 734 to reconstruct a PET image using a CT image for attenuation correction and gating data acquired under similar conditions to the depth and amount of change of respiration during scanning of the CT image. Therefore, the reconstruction function 734 can generate a high-quality attenuation-corrected PET image that suppresses the influence of respiratory movement, as in the above example.

[0084] Hereinafter, an example of the scan processing performed by the processing circuitry 73 of the PET-CT device 1 will be described with reference to Fig. 6. Fig. 6 is a flow chart showing an example of the scan processing performed by the processing circuitry 73 of the PET-CT device 1. In this process, a scan processing will be described in which a CT image for attenuation correction is acquired, and then a PET image is reconstructed using the CT image.

[0085] First, the imaging control function 733 controls the CT gantry 30 to execute a CT scan to obtain a CT image for attenuation correction (step S51). Next, the respiratory waveform acquisition function 732 cooperates with the monitor control function 731 to acquire a CT respiratory waveform from the monitor data obtained by the infrared camera 60 (step S52). In addition, the reconstruction function 734 identifies the CT respiratory phase at the time the CT scan was performed from the CT respiratory waveform based on the time the CT scan was performed (step S53).

[0086] Furthermore, when the CT scan is completed, the reconstruction function 734 reconstructs a CT image for attenuation correction based on the CT raw data obtained by the CT scan (step S54).

[0087] Next, the imaging control function 733 controls the PET gantry to perform a PET scan (step S55). Next, the respiratory waveform acquisition function 732 cooperates with the monitor control function 731 to acquire a PET respiratory waveform from the monitor data obtained by the infrared camera 60 (step S56).

[0088] Next, the imaging control function 733 extracts PET raw data acquired during the PET respiratory phase corresponding to the CT respiratory phase based on the CT respiratory phase identified in step S53 and the PET respiratory waveform, and generates gate data (step S57).

[0089] Then, the imaging control function 733 reconstructs a PET image based on the extracted gate data and the CT image for attenuation correction (step S58), and ends this process.

[0090] The PET-CT device 1 described above scans the subject P to obtain a CT image for attenuation correction, and identifies the CT respiratory phase of the subject P when the CT image was scanned. The PET-CT device 1 also obtains PET scan data based on gamma rays emitted from the subject P, and generates gate data by gating the PET scan data based on the CT respiratory phase. The PET-CT device 1 then reconstructs a PET image based on the CT image for attenuation correction and the gate data.

[0091] From these facts, the PET-CT device 1 according to this embodiment can reconstruct a PET image with attenuation correction using a CT image for attenuation correction and gating data acquired under the same condition as the respiratory phase during scanning of the CT image. That is, the PET-CT device 1 can improve the synchronization accuracy of the respiratory phase between the CT image and the PET raw data when reconstructing a PET image, so that a PET image with attenuation correction can be generated while suppressing the influence of respiratory movement. Therefore, the PET-CT device 1 can improve the image quality of a PET image using a CT image for attenuation correction.

[0092] The above-described embodiment can be modified as appropriate by changing a part of the configuration or function of the PET-CT device 1. Therefore, some modified examples of the above-described embodiment will be described below as other embodiments. The following mainly describes the differences from the above-described embodiment, and the details of the commonalities with the contents already described will be omitted. The modified examples described below may be implemented individually or in appropriate combination.

[0093] (Variation 1) In the above embodiment, a configuration has been described in which the infrared camera 60 is used as a monitoring device for monitoring the breathing of the subject P, but the monitoring device is not limited to the infrared camera 60. For example, the monitoring device may be an imaging device that captures images in a frequency band other than infrared.

[0094] As an example, the monitoring device may be a terahertz camera that captures images in the terahertz band. The terahertz camera detects radio wave energy in the terahertz band emitted from an object. By using the terahertz camera as the monitoring device, the monitoring device outputs monitor data that represents the temperature difference between the radio wave energy in the terahertz band emitted from a human body (body temperature is the heat source) and the radio wave energy in the terahertz band emitted from an object other than the human body.

[0095] In this case, the respiratory waveform acquisition function 732 acquires the respiratory waveform of the subject P from the monitor data output by the terahertz camera based on the image changes (temperature changes) at the boundary between the human body area and other areas and the temperature changes of the human body parts, as in the above-mentioned embodiment.

[0096] Furthermore, by using a terahertz camera, just like an infrared camera, it is possible to obtain the respiratory waveform of the subject P from the monitor data output by the terahertz camera, even when it is used in a dark place or when the subject P is covered with a drape or the like.

[0097] As another example, the monitoring device may be an optical camera such as a digital camera that captures images in the visible light band. When the optical camera is used as the monitoring device, for example, a marker is placed on the abdomen or the like of the subject P, and the optical camera captures an image of the region of the human body where the marker is placed.

[0098] In this case, the respiratory waveform acquisition function 732 detects the movement of the marker (movement associated with the breathing of the subject P) represented in the monitor data output by the optical camera, and acquires the respiratory waveform of the subject P based on the detected movement of the marker.

[0099] In this way, even if a monitoring device other than the infrared camera 60 is used, the respiratory waveform of the subject P can be acquired in a non-contact manner, as in the above-mentioned embodiment. Therefore, the PET-CT device 1 according to this modification can achieve the same effects as the above-mentioned embodiment.

[0100] (Variation 2) In the above embodiment, a configuration has been described in which the respiratory waveform of the subject P is acquired from monitor data of the monitoring device (infrared camera 60), but information other than the respiratory waveform may also be acquired.

[0101] For example, the monitor data includes not only the respiratory dynamics of the subject P, but also the body movement of the subject P when the subject P moves. Since body movement during scanning can cause artifacts, it is preferable to exclude data when body movement occurs from the reconstruction target.

[0102] Therefore, for example, the respiratory waveform acquisition function 732 detects body movements other than breathing of the subject P from the monitor data, and records the time when the body movements occurred in association with the respiratory waveform. Specifically, the respiratory waveform acquisition function 732 records the time when the body movements occurred in association with the PET respiratory waveform during the PET scan. Then, the reconstruction function 734 removes the time when the body movements occurred from the PET respiratory waveform, identifies the respiratory period corresponding to the CT phase, extracts the PET raw data acquired during the respiratory period, and generates gate data. Note that the reconstruction function 734 of this modification corresponds to the second identification unit.

[0103] As a result, the PET-CT device 1 according to this modification can perform reconstruction by excluding the PET raw data at the time when the subject P moves. Therefore, the PET-CT device 1 according to this modification can acquire a higher quality PET image with reduced artifacts caused by the body movement.

[0104] Furthermore, when the infrared camera 60 is used as a monitoring device, the monitor data of the monitoring device also includes information indicating the body temperature of the subject P. The body temperature of the subject P can be used clinically, such as to determine the condition of the subject P.

[0105] Therefore, for example, the processing circuitry 73 including the respiratory waveform acquisition function 732 may acquire body temperature information indicating the body temperature of the subject P from the monitor data of the infrared camera 60. In addition, the processing circuitry 73 may store the body temperature information of the subject P acquired from the monitor data together with the PET image, or output it to the display 74.

[0106] This allows the PET-CT device 1 to make secondary clinical use of the body temperature information of the subject P obtained during scanning. Note that the output destination of the body temperature information is not limited to the display 74. For example, the processing circuitry 73 may output the body temperature information of the subject P together with a subject ID for identifying the subject P to an external device or system such as a RIS.

[0107] In the above embodiment, the functional configuration of the PET-CT device 1 is realized by the processing circuitry 73, but the embodiment is not limited to this. For example, the functional configuration in this specification may be realized by hardware alone or a combination of hardware and software.

[0108] Furthermore, the term "processor" used in the above description means a circuit such as a CPU, MPU, GPU, ASIC, or programmable logic device (e.g., SPLD, CPLD, and FPGA). The processor realizes its function by reading and executing a program stored in memory 75. Instead of storing a program in memory 75, the processor may be configured to directly incorporate the program into its circuit. In this case, the processor realizes its function by reading and executing the program incorporated in the circuit. Furthermore, the processor of this embodiment is not limited to being configured as a single circuit, and may be configured as a single processor by combining multiple independent circuits to realize its function.

[0109] Here, the program executed by the processor is provided in advance in a ROM, a storage circuit, or the like. The program may be provided by being recorded in a computer-readable 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 functional units. As actual hardware, a CPU reads out and executes the program from a storage medium such as a ROM, and each module is loaded onto a main storage device and generated on the main storage device.

[0110] According to at least one of the embodiments described above, it is possible to improve the image quality of a PET image in which a CT image is used for attenuation correction.

[0111] 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 embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations 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 described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0112] 1 PET-CT device 10 PET Gantry 30 CT Gantry 50 berths 60 Infrared Camera 70 Console 73 Processing Circuit 731 Monitor control function 732 Respiratory waveform acquisition function 733 Imaging control function 734 Reconfiguration function 735 Image Processing Function 736 Display Control Function

Claims

1. A first acquisition unit that acquires first data from a camera configured to image a subject while a CT scanner is scanning the subject and to image the subject while a PET scanner is detecting gamma rays; a generating unit that generates, based on second data acquired by the CT scanner, correction data for attenuation correction corresponding to a respiratory phase of the subject identified based on the first data; a first identifying unit that identifies a first period in which no body movement other than breathing of the subject occurs from a period in which the PET scanner detects gamma rays based on the first data; a second identification unit that identifies a second period corresponding to both a period corresponding to the respiratory phase identified based on the first data and the first period identified based on the first data; a reconstruction processing unit that reconstructs a PET image based on the correction data and PET scan data of the PET scanner, excluding a third period corresponding to the second period and in which a body movement other than breathing of the subject occurs; A PET-CT device comprising:

2. A second acquisition unit that acquires a respiratory waveform of the subject from the first data; a third identification unit that identifies a respiratory phase of the subject from the respiratory waveform; Further comprising: The PET-CT device according to claim 1.

3. The camera is an infrared camera that visualizes infrared rays emitted from the subject. The PET-CT device according to claim 1.

4. The camera is a terahertz camera that visualizes terahertz band radio waves emitted from the subject. The PET-CT device according to claim 1.

5. The camera is an optical camera that photographs a marker placed on the body of the subject. The PET-CT device according to claim 1.

6. A PET-CT device as described in claim 1, wherein the generation unit does not use second data corresponding to a respiratory phase other than the respiratory phase identified based on the first data to generate the correction data.

7. A step of acquiring first data from a camera configured to image a subject while a CT scanner is scanning the subject and to image the subject while a PET scanner is detecting gamma rays; generating, based on second data acquired by the CT scanner, correction data for attenuation correction corresponding to the respiratory phase of the subject identified based on the first data; identifying a first period in which no body movement other than breathing of the subject occurs from a period in which the PET scanner detects gamma rays based on the first data; identifying a second period corresponding to both a period corresponding to the respiratory phase identified based on the first data and the first period identified based on the first data; reconstructing a PET image based on the correction data and PET scan data of the PET scanner excluding a third period corresponding to the second period and in which a body movement other than respiration of the subject occurs; A medical image processing method comprising:

Images