Image acquisition device and image acquisition method

Abstract

An image acquisition device (1A) is provided with a measurement unit (10) and a processing unit (20). The processing unit (20) performs simultaneous counting of a pair of gamma-ray photons generated by pair annihilation of electrons / positron in the positron emission nuclide (81) by the first detector (11) and the second detector (12). Gamma-ray photons coming to one of the first detector (11) and the second detector (12) are photons coming without Compton scattering in the subject (90), and gamma-ray photons coming to the other of the first detector (11) and the second detector (12) are photons coming after Compton scattering in the subject (90). The position at which Compton scattering occurs in the subject (90) of the gamma-ray photons is determined on the basis of the position of the positron emission nuclide (81) and the detection position and the detection time of the gamma-ray photons obtained by the first detector (11) and the second detector (12), respectively. As a result, it is possible to obtain a tomographic image representing anatomical information of a subject without performing image reconstruction processing, and to obtain an image acquisition method.

Description

Technical Field

[0001] The present invention relates to an image acquisition device and an image acquisition method. Background Art

[0002] Nuclear medicine diagnostic devices such as PET (Positron Emission Tomography) devices and SPECT (Single Photon Emission Computed Tomography) devices can obtain tomographic images of a subject to which a drug labeled with a positron-emitting nuclide or a single-photon-emitting nuclide has been administered. The tomographic images obtained by these nuclear medicine diagnostic devices represent the distribution of the positron-emitting nuclide or the single-photon-emitting nuclide in the subject (distribution of the drug), and can be used for diagnosis of the health status of the subject, etc.

[0003] The X-ray CT apparatus can also obtain a three-dimensional tomographic image of the subject. The tomographic image obtained by the X-ray CT apparatus represents anatomical information of the subject. Hereinafter, the tomographic image is assumed to be a three-dimensional tomographic image.

[0004] The image quality of PET images is improved by using a PET device and an X-ray CT device together and correcting the PET images using the anatomical information obtained by the X-ray CT device. However, since the X-ray CT device is expensive, research and development of an inexpensive device that can obtain a tomographic image showing the anatomical information of the subject is underway.

[0005] Each of Non-Patent Document 1 and Patent Document 1 describes an apparatus capable of acquiring both a tomographic image showing the distribution of positron-emitting nuclides in a subject and a tomographic image showing anatomical information.

[0006] The device described in non-patent document 1 has a structure of a PET device in which a plurality of detectors are arranged around a measurement space in which a subject is placed. The device uses a detector having an LSO (Lu2SiO5:Ce) scintillator, and detects gamma rays that have passed through the subject from among gamma rays of energy 307keV or 202keV emitted from 176Lu contained in the LSO scintillator of each detector by other detectors. Then, the device performs image reconstruction processing based on the detection result of gamma rays of energy 307keV or 202keV, and obtains a tomographic image representing anatomical information of the subject.

[0007] The device described in Patent Document 1 uses an electron trajectory tracking Compton camera (ETCC, Electron Tracking Compton Camera). Conventional Compton cameras estimate that gamma rays are coming from any position on a conical surface called a Compton cone based on energy information in each of the scatterer and absorber. In contrast, ETCC uses a gas detector to track the trajectory of the recoil electrons, and can uniquely lock the direction of the gamma rays.

[0008] The device detects the direction of gamma rays generated in a subject to which a drug labeled with a positron-emitting nuclide is administered, and the gamma rays are Compton scattered in the subject and have their energy reduced by ETCC. Then, based on the detection result of the direction of gamma rays obtained by ETCC, the device uses an analytical method or a statistical method, that is, by performing image reconstruction processing to obtain a tomographic image representing anatomical information of the subject.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent No. 6990412

[0012] Non-patent literature

[0013] Non-patent document 1: Mohammadreza Teimoorisichani et al., "A CT-less approach to quantitative PET imaging using the LSO intrinsic radiation for long-axialFOV PET scanners", Med.Phys.Vol.49, pp.309-323, 2022

[0014] Non-patent document 2: Gerard Arino-Estrada et al., "First Cerenkov charge-induction(CCI)TlBr detector for TOF-PET and proton range verification", Phys.Med.Biol.64 175001, 2019 Summary of the invention

[0015] Problems to be solved by the invention

[0016] The techniques described in both Non-Patent Document 1 and Patent Document 1 require image reconstruction based on gamma ray detection results in order to obtain a tomographic image showing anatomical information of the subject. The tomographic image obtained by the image reconstruction process has reduced image quality due to the image reconstruction process, and the anatomical information is degraded.

[0017] An object of the present invention is to provide an image acquisition apparatus and an image acquisition method capable of acquiring a tomographic image representing anatomical information of a subject without performing image reconstruction processing.

[0018] Technical means of solving problems

[0019] An embodiment of the present invention is an image acquisition device. The image acquisition device comprises: (1) a measuring unit, which includes a first detector and a second detector each detecting a gamma ray photon, and outputs a signal indicating a detection position and a detection time when the first detector and the second detector respectively detect a gamma ray photon; and (2) a processing unit, which processes the signals respectively output from the first detector and the second detector; (3) the measuring unit, in a first measuring mode, places a subject between the first detector and the second detector, and places a positron emitting nuclide between the first detector or the second detector and the subject, and outputs a signal indicating a detection position and a detection time of the gamma ray photon respectively obtained by the first detector and the second detector; (4) the processing unit, in the first measuring mode, processes the signals respectively output from the first detector and the second detector; The second detector simultaneously counts a pair of gamma-ray photons generated by the annihilation of electrons / positrons in a positron-emitting nuclide, and for each simultaneous counting phenomenon, the gamma-ray photons arriving at one of the first detector and the second detector are assumed to be photons arriving without Compton scattering in the subject, and the gamma-ray photons arriving at the other detector are assumed to be photons arriving after Compton scattering in the subject. Based on the detection position and detection time of the gamma-ray photons obtained by the first detector and the second detector respectively and the position of the positron-emitting nuclide, the position where Compton scattering of the gamma-ray photons occurs in the subject is calculated, and a first tomographic image showing the distribution of the Compton scattering positions in the subject calculated for each of the multiple simultaneous counting phenomena is produced.

[0020] An embodiment of the present invention is an image acquisition device. The image acquisition device comprises: (1) a measuring unit including a first detector and a second detector each detecting a gamma-ray photon, and outputting a signal indicating a detection position and a detection time when the first detector and the second detector respectively detect a gamma-ray photon; and (2) a processing unit processing the signals respectively outputted from the first detector and the second detector, (3) when a subject to which a drug labeled with a positron-emitting nuclide is administered is placed between the first detector and the second detector, and a positron-emitting nuclide is placed between the first detector or the second detector and the subject, the measuring unit outputting a signal indicating a detection position and a detection time of the gamma-ray photon respectively obtained by the first detector and the second detector, and (4) a processing unit for each simultaneous counting phenomenon in which the first detector and the second detector simultaneously count a pair of gamma-ray photons generated by an electron / positron annihilation phenomenon in the positron-emitting nuclide, (a) when the gamma-ray photon arriving at one of the first detector and the second detector is not present in the subject, (a) in the case where the photons arriving are Compton scattered and the gamma-ray photons arriving on the other side are photons arriving after Compton scattering in the subject, the position where the gamma-ray photons in the subject are Compton scattered is determined based on the detection position and detection time of the gamma-ray photons obtained by the first detector and the second detector respectively, and the position of the positron-emitting nuclide placed between the first detector or the second detector and the subject; (b) in the case where the gamma-ray photons arriving on both the first detector and the second detector are photons arriving without Compton scattering in the subject, the position where the pair annihilation phenomenon occurs is determined based on the detection position and detection time of the gamma-ray photons obtained by the first detector and the second detector respectively; (c) a first tomographic image showing the distribution of the Compton scattering positions in the subject obtained for each of a plurality of simultaneous counting phenomena is prepared, a second tomographic image showing the distribution of the occurrence positions of the pair annihilation phenomenon in the subject obtained for each of a plurality of simultaneous counting phenomena is prepared, and the second tomographic image is corrected based on the first tomographic image.

[0021] An embodiment of the present invention is an image acquisition method. The image acquisition method comprises: (1) a measurement step, which uses a first detector and a second detector each detecting a gamma ray photon, and outputs a signal indicating a detection position and a detection time when the first detector and the second detector respectively detect a gamma ray photon; and (2) a processing step, which processes the signals respectively output from the first detector and the second detector, (3) in the measurement step, in a first measurement mode, a subject is placed between the first detector and the second detector, and a positron emitting nuclide is placed between the first detector or the second detector and the subject, and outputs a signal indicating a detection position and a detection time of the gamma ray photon respectively obtained by the first detector and the second detector, and (4) in the processing step, in the first measurement mode, for the first detector In each simultaneous counting phenomenon in which the first detector and the second detector simultaneously count a pair of gamma-ray photons generated by the annihilation phenomenon of electron / positron in the positron-emitting nuclide, it is assumed that the gamma-ray photons arriving at one of the first detector and the second detector are photons arriving without Compton scattering in the subject, and it is assumed that the gamma-ray photons arriving at the other detector are photons arriving after Compton scattering in the subject. Based on the detection position and detection time of the gamma-ray photons obtained by the first detector and the second detector respectively and the position of the positron-emitting nuclide, the position where Compton scattering of the gamma-ray photons occurs in the subject is calculated, and a first tomographic image representing the distribution of the Compton scattering positions in the subject calculated for each of the multiple simultaneous counting phenomena is prepared.

[0022] An embodiment of the present invention is an image acquisition method. The image acquisition method comprises: (1) a measurement step, which uses a first detector and a second detector each detecting a gamma-ray photon, and outputs a signal indicating a detection position and a detection time when the first detector and the second detector respectively detect a gamma-ray photon; and (2) a processing step, which processes the signals respectively output from the first detector and the second detector, (3) when a subject to which a drug labeled with a positron-emitting nuclide is administered is placed between the first detector and the second detector, and a positron-emitting nuclide is placed between the first detector or the second detector and the subject, the measurement step outputs a signal indicating a detection position and a detection time of the gamma-ray photon respectively obtained by the first detector and the second detector, and (4) a processing step, for each simultaneous counting phenomenon in which the first detector and the second detector simultaneously count a pair of gamma-ray photons generated by an electron / positron annihilation phenomenon in a positron-emitting nuclide, (a) when a gamma-ray photon arriving at one of the first detector and the second detector is in the subject (a) when one of the gamma-ray photons arriving at the first detector and the second detector is a photon arriving without Compton scattering in the subject, and the other gamma-ray photon arriving at the other side is a photon arriving after Compton scattering in the subject, the position where the gamma-ray photon in the subject is Compton scattered is determined based on the detection position and detection time of the gamma-ray photon obtained by the first detector and the second detector, and the position of the positron-emitting nuclide placed between the first detector or the second detector and the subject; (b) when the gamma-ray photons arriving at both the first detector and the second detector are photons arriving without Compton scattering in the subject, the position where the pair annihilation phenomenon occurs is determined based on the detection position and detection time of the gamma-ray photon obtained by the first detector and the second detector; (c) a first tomographic image showing the distribution of the Compton scattering positions in the subject obtained for each of the multiple simultaneous counting phenomena is prepared, a second tomographic image showing the distribution of the occurrence positions of the pair annihilation phenomenon in the subject obtained for each of the multiple simultaneous counting phenomena is prepared, and the second tomographic image is corrected based on the first tomographic image.

[0023] Effects of the Invention

[0024] According to the embodiment of the present invention, a tomographic image representing anatomical information of a subject can be acquired without performing image reconstruction processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a diagram showing the configuration of the image acquisition apparatus 1A according to the first embodiment (particularly, a diagram for explaining acquisition of a first tomographic image in a first measurement mode).

[0026] Figure 2This is a diagram for explaining a method of finding the position where Compton scattering of gamma-ray photons occurs in a subject.

[0027] Figure 3 It is a diagram showing the configuration of the image acquisition apparatus 1A according to the first embodiment (particularly, a diagram for explaining acquisition of a second tomographic image in the second measurement mode).

[0028] Figure 4 It is a diagram showing the configuration of an image acquisition device 1B according to the second embodiment.

[0029] Figure 5 It is a diagram showing the configuration of an image acquisition device 1C according to the third embodiment.

[0030] Figure 6 It is a diagram showing the configuration of an image acquisition device 1D according to a fourth embodiment.

[0031] Figure 7 It is a diagram showing the configuration of an image acquisition device 1E according to the fifth embodiment.

[0032] Figure 8 It is a diagram showing the configuration of an image acquisition device 1F according to the sixth embodiment.

[0033] Fig. 9 (a) and (b) are diagrams for explaining changes in the field of view of the device when the positron emitting nuclide 81 is moved in a direction parallel to the detection surface of the first detector 11 in the measurement unit 10F of the image acquisition device 1F according to the sixth embodiment.

[0034] Fig.10 (a) and (b) are diagrams for explaining the image quality of the first tomographic image when the positron emitting nuclide 81 is moved in the direction perpendicular to the detection surface of the first detector 11 in the measurement unit 10F of the image acquisition device 1F according to the sixth embodiment.

[0035] Fig.11 It is a diagram showing the structure and arrangement of the measurement unit assumed in the simulation.

[0036] Fig.12 This is a diagram showing the structure of a phantom assumed as the subject 90 in the simulation.

[0037] Fig.13 FIG. 1 is a diagram showing a first tomographic image obtained by simulation. DETAILED DESCRIPTION

[0038] Hereinafter, embodiments of the image acquisition device and the image acquisition method will be described in detail with reference to the accompanying drawings. In addition, in the description of the accompanying drawings, the same elements are marked with the same symbols, and repeated descriptions are omitted. The present invention is not limited to these examples, and is intended to include all changes within the meaning and scope of the claims and equivalent to the claims.

[0039] (First Embodiment)

[0040] Figure 1 1 is a diagram showing the structure of an image acquisition device 1A according to the first embodiment. The image acquisition device 1A includes a measuring unit 10, a processing unit 20, and a display unit 30. The measuring unit 10 includes a first detector 11 and a second detector 12 arranged opposite to each other with a subject 90 sandwiched therebetween. The first detector 11 and the second detector 12 detect gamma ray photons, respectively, and output signals indicating a detection position and a detection time when a gamma ray photon is detected.

[0041] The processing unit 20 processes the signals outputted from the first detector 11 and the second detector 12, and creates a tomographic image of the subject 90. The display unit 30 displays the tomographic image created by the processing unit 20. The processing unit 20 and the display unit 30 may be constituted by a computer, for example.

[0042] As each of the first detector 11 and the second detector 12, for example, a Cherenkov detector can be used. The Cherenkov detector is configured to include a Cherenkov radiator (for example, lead glass, lead fluoride PbF2, hafnium oxide HfO2, etc.) and a built-in microchannel plate photomultiplier tube (MCP-PMT). The Cherenkov detector can be, for example, a structure in which small detectors each having no position detection capability are arranged in a two-dimensional manner, or a structure in which a Cherenkov radiator and a multi-anode MCP-PMT are combined.

[0043] In addition, the Cherenkov detector can also be used to detect BGO (Bi4Ge3O 12 ) is used as a Cherenkov radiator. The low-speed scintillator interacts with gamma rays, first emitting Cherenkov light and then emitting scintillation light, so it can be used as a Cherenkov radiator and can achieve high time resolution. As a result, a detector that is cheaper than LSO scintillators can be constructed.

[0044] In addition, each of the first detector 11 and the second detector 12 may be, for example, a semiconductor detector with high time resolution. A semiconductor detector with high time resolution uses, for example, thallium bromide (TlBr) and is provided with an electrode for charge collection and a high time resolution photodetector. Such a detector may be, for example, a detector described in non-patent document 2. By using a semiconductor detector, energy resolution is improved, and as a result, it can be expected that the ability to remove scattered components can be improved, and image quality can be improved.

[0045] Considering that the spatial resolution of a tomographic image obtained by a nuclear medicine diagnostic apparatus such as a PET apparatus is about 3 to 5 mm, it is desirable that the spatial resolution required of each of the first detector 11 and the second detector 12 is equal to or better than that. Similarly, it is desirable that the temporal resolution required of each of the first detector 11 and the second detector 12 is 20 to 35 ps or less in terms of simultaneous counting temporal resolution.

[0046] When each of the first detector 11 and the second detector 12 includes a Cherenkov radiator or a scintillator, it is preferred that the first detector 11 and the second detector 12 output a signal indicating the position (detection position) and the time (detection time) of the gamma ray interaction in the Cherenkov radiator or the scintillator instead of the position and time when the Cherenkov light or the scintillation light is detected. In this case, the detection position is expressed not only by the position in two directions parallel to the detection surface of the detector, but also by a three-dimensional coordinate value that also determines the position in the perpendicular direction.

[0047] The detection surface of each of the first detector 11 and the second detector 12 preferably has a size larger than the subject 90 (or the region of interest in the subject 90). For example, in the case of an image acquisition device that acquires a tomographic image of a human brain, the detection surface of each of the first detector 11 and the second detector 12 preferably has a size that is approximately the same as or larger than the size of the human brain.

[0048] The image acquisition device 1A and the image acquisition method using the same acquire a tomographic image (first tomographic image) of the subject 90 in the first measurement mode. The image acquisition device 1A and the image acquisition method can also acquire a tomographic image (second tomographic image) of the subject 90 in the second measurement mode.

[0049] The first tomographic image is an image showing the distribution of Compton scattering positions in the subject 90, and shows anatomical information of the subject 90. The second tomographic image shows the distribution of positron-emitting nuclides (drug distribution) in the subject 90, and can be used for diagnosis of the health status of the subject 90.

[0050] Acquisition of the first tomographic image in the first measurement mode is performed through the first measurement step and the first processing step as described below. Figure 1 It is a diagram showing the configuration of the image acquisition apparatus 1A according to the first embodiment, and particularly a diagram for explaining acquisition of a first tomographic image in the first measurement mode.

[0051] In the first measurement step, the subject 90 is placed between the first detector 11 and the second detector 12. At this time, the positron emitting nuclide may not be administered to the subject 90. A positron emitting nuclide 81 is placed between the first detector 11 or the second detector 12 and the subject 90. It is preferable to use a nuclide as small as possible for the positron emitting nuclide 81. In this figure, a positron emitting nuclide 81 is placed between the first detector 11 and the subject 90.

[0052] The positron emitted from the positron emitting nuclide 81 is immediately annihilated with an electron located nearby, and a pair of gamma ray photons flying in opposite directions are generated by the electron / positron annihilation phenomenon. If the first detector 11 and the second detector 12 detect gamma rays, they output signals indicating the detection position and detection time of the gamma ray photons.

[0053] In the first processing step, the processing unit 20, for each simultaneous counting phenomenon in which the first detector 11 and the second detector 12 simultaneously count a pair of gamma-ray photons generated by the annihilation phenomenon of electron / positron in the positron-emitting nuclide 81, assumes that the gamma-ray photons arriving at one of the first detector 11 and the second detector 12 are photons that arrive without Compton scattering in the subject, and assumes that the gamma-ray photons arriving at the other side are photons that arrive after Compton scattering in the subject, and based on the detection position and detection time of the gamma-ray photons obtained by the first detector 11 and the second detector 12 respectively and the position of the positron-emitting nuclide 81, the position where the gamma-ray photons undergo Compton scattering is calculated.

[0054] Then, the processing unit 20 creates a first tomographic image showing the distribution of Compton scattering positions in the subject 90 obtained for each of the plurality of simultaneous counting events. The first tomographic image shows anatomical information of the subject 90 .

[0055] The processing unit 20 can determine whether the gamma ray photons arriving at the first detector 11 or the second detector 12 have undergone Compton scattering based on any one or more of the position of the positron emitting nuclide 81, the energy of the gamma ray photons, and the detection times of the gamma ray photons obtained by the first detector 11 and the second detector 12 respectively.

[0056] like Figure 1As shown, if a positron emitting nuclide 81 is placed between the first detector 11 and the subject 90, it can be determined that the gamma rays reaching the first detector 11 have not undergone Compton scattering in the subject. The energy of a pair of gamma ray photons generated by the annihilation of electron / positron pairs is 511keV, but the energy of the gamma rays becomes lower due to Compton scattering, so it can be determined based on the magnitude of the energy of the gamma rays whether Compton scattering has occurred. Based on the causal relationship between the detection times of the gamma ray photons obtained by the first detector 11 and the second detector 12, it can be determined whether Compton scattering has occurred in the subject.

[0057] Figure 2 This is a diagram for explaining a method of finding the position where the gamma ray photon Compton scatters in the subject. The position of the positron emitting nuclide 81 is set to P, the detection position of the gamma ray obtained by the first detector 11 is set to R1, the detection position of the gamma ray obtained by the second detector 12 is set to R2, and the position where the gamma ray Compton scatters is set to C. The detection time of the gamma ray obtained by the first detector 11 is set to t1, and the detection time of the gamma ray obtained by the second detector 12 is set to t2.

[0058] The flight distance of one of the pair of gamma ray photons generated by the electron / positron annihilation phenomenon in the positron emitting nuclide 81 is the distance d1 from the position P to the position R1. The flight distance of the other gamma ray is the distance d from the position P to the position C. 21 and the distance d from position C to position R2 22 The sum (d 21 +d 22 ).

[0059] The difference in the flight distance of a pair of gamma-ray photons (d 21 +d 22 -d1) is equal to the value obtained by multiplying the difference in the detection time of these gamma-ray photons (t2-t1) by the speed of light c. In addition, the line segment connecting the position P and the position R1 is parallel to the line segment connecting the position P and the position C. According to the above, based on the detection position R1 and the detection time t1 of the gamma-ray photons obtained by the first detector 11, the detection position R2 and the detection time t2 of the gamma-ray photons obtained by the second detector 12, and the position P of the positron emitting nuclide 81, the position C where the gamma-ray photons undergo Compton scattering can be obtained.

[0060] In the case where neither side of a pair of gamma-ray photons undergoes Compton scattering, Figure 2 The Compton scattering position obtained by the method described in accords with the position P of the positron emitting nuclide 81. This position is outside the subject 90 and can therefore be easily excluded.

[0061] Acquisition of the second tomographic image in the second measurement mode is performed through the second measurement step and the second processing step as described below. Figure 3 This is a diagram showing the configuration of the image acquisition apparatus 1A according to the first embodiment, and particularly a diagram for explaining acquisition of a second tomographic image in the second measurement mode.

[0062] In the second measurement step, the subject 90 to which the medicine labeled with the positron-emitting nuclide 83 is administered is placed between the first detector 11 and the second detector 12. At this time, the positron-emitting nuclide may not be placed outside the subject 90. A pair of gamma-ray photons flying in opposite directions are generated by the annihilation phenomenon of the electron / positron pair in the positron-emitting nuclide 83 that labels the medicine administered to the subject 90. If the first detector 11 and the second detector 12 detect gamma rays, respectively, signals indicating the detection position and detection time of the gamma-ray photons are output.

[0063] It is preferred that the positron emitting nuclide 83 used to label the drug administered to the subject 90 in the second measurement step is the same type as the positron emitting nuclide 81 placed between the first detector 11 and the subject 90 in the first measurement step. By making the positron emitting nuclide 83 and the positron emitting nuclide 81 the same type, only one type of positron emitting nuclide is required, so that measurement preparation becomes easy. In addition, the positron emitting nuclide 81 may also be a calibration positron emitting nuclide such as 68Ge / 68Ga.

[0064] In the second processing step, the processing unit 20 obtains the position where the pair annihilation phenomenon occurs based on the detection position and detection time of the gamma-ray photons obtained by the first detector 11 and the second detector 12 for each simultaneous counting phenomenon in which the first detector 11 and the second detector 12 simultaneously count a pair of gamma-ray photons generated by the pair annihilation phenomenon of the electron / positron in the positron-emitting nuclide 83. The position where the pair annihilation event occurs for each simultaneous counting phenomenon can be obtained based on the difference between the detection times of the gamma-ray photons obtained by the first detector 11 and the second detector 12 on the line segment connecting the detection positions of the gamma-ray photons obtained by the first detector 11 and the second detector 12.

[0065] Then, the processing unit 20 creates a second tomographic image showing the distribution of the locations where the annihilation phenomena occur in the subject 90 obtained for each of the plurality of simultaneous counting phenomena. Since the first detector 11 and the second detector 12 have good time resolution, the second tomographic image can be obtained as a three-dimensional tomographic image without performing image reconstruction processing.

[0066] The second tomographic image shows the distribution of the positron emitting nuclide 83 (drug distribution) in the subject 90 and can be used for diagnosis of the health status of the subject 90. The processing unit 20 can also obtain a second tomographic image in which the gamma ray absorption distribution in the subject 90 is corrected by correcting the second tomographic image based on the first tomographic image.

[0067] Either the acquisition of the first tomographic image based on the first measurement mode or the acquisition of the second tomographic image based on the second measurement mode may be performed first. However, if the acquisition of the second tomographic image based on the second measurement mode is performed first, the annihilation phenomenon of the positron emitting nuclide 83 administered to the subject 90 at this time may affect the acquisition of the first tomographic image based on the first measurement mode thereafter, so it is preferable to first acquire the first tomographic image based on the first measurement mode.

[0068] In this embodiment, a tomographic image (first tomographic image) representing anatomical information of the subject 90 can be obtained without performing image reconstruction processing, thereby avoiding the reduction in image quality caused by image reconstruction processing and the degradation of anatomical information. In addition, a tomographic image (second tomographic image) representing the distribution of positron-emitting nuclides (distribution of the drug) in the subject can be obtained without performing image reconstruction processing.

[0069] In this embodiment, since a large rotating structure like an X-ray CT apparatus is not required, a compact and inexpensive apparatus can be provided. In addition, in this embodiment, the radiation dose of the subject can be reduced compared to the case of using an X-ray CT apparatus.

[0070] The device described in non-patent document 1 has a structure of a PET device in which a plurality of detectors are arranged around a measurement space where a subject is placed, so it is difficult to miniaturize it. In addition, since an LSO scintillator containing lutetium Lu, which is a rare material, is used, it is difficult to reduce the price. In contrast, in the present embodiment, these problems are eliminated, and miniaturization and low price can be achieved.

[0071] Since the device described in Patent Document 1 uses a gas detector, it is difficult to improve the detection efficiency. In contrast, in the present embodiment, this problem does not exist and the detection efficiency can be improved.

[0072] (Second Embodiment)

[0073] Figure 41 is a diagram showing the configuration of an image acquisition device 1B according to the second embodiment. The image acquisition device 1B includes a measurement unit 10, a processing unit 20, and a display unit 30. The second embodiment is different from the first embodiment in that the Compton scattering position in the subject 90 and the position where the pair annihilation phenomenon occurs in the subject 90 are obtained in a common period.

[0074] In the measurement step, the subject 90 to which the drug labeled with the positron emitting nuclide 83 is administered is placed between the first detector 11 and the second detector 12. In addition, the positron emitting nuclide 81 is placed between the first detector 11 or the second detector 12 and the subject 90. In this figure, the positron emitting nuclide 81 is placed between the first detector 11 and the subject 90.

[0075] By making the positron emitting nuclide 83 for labeling the drug administered to the subject 90 and the positron emitting nuclide 81 placed between the first detector 11 and the subject 90 the same type, only one type of positron emitting nuclide is required, so that the measurement preparation becomes easy. In addition, the positron emitting nuclide 81 may also be a calibration positron emitting nuclide such as 68Ge / 68Ga.

[0076] A pair of gamma ray photons flying in opposite directions are generated by the electron / positron annihilation phenomenon in each of the positron emitting nuclides 81 and 83. When the first detector 11 and the second detector 12 detect gamma rays, they output signals indicating the detection position and detection time of the gamma ray photons.

[0077] In the processing step, the processing unit 20 performs the following processing for each simultaneous counting phenomenon in which the first detector 11 and the second detector 12 simultaneously count a pair of gamma-ray photons generated by the electron / positron pair annihilation phenomenon in the positron-emitting nuclide 81 or the positron-emitting nuclide 83 .

[0078] The processing unit 20 determines whether the gamma ray photons arriving at the first detector 11 or the second detector 12 have undergone Compton scattering based on the position of the positron emitting nuclide 81, the energy of the gamma ray photons, and any one or more of the detection times of the gamma ray photons obtained by the first detector 11 and the second detector 12 respectively.

[0079] In the case where the processing unit 20 determines that the gamma-ray photons arriving at one of the first detector 11 and the second detector 12 are photons arriving without Compton scattering in the subject, and the gamma-ray photons arriving at the other detector are photons arriving after Compton scattering in the subject, the processing unit 20 assumes that the pair of gamma-ray photons are photons arriving from the positron-emitting nuclide 81 outside the subject 90, and uses Figure 2 The calculation described above finds the position where the gamma-ray photons are Compton scattered in the subject 90 based on the detection position and detection time of the gamma-ray photons obtained by the first detector 11 and the second detector 12 and the position of the positron-emitting nuclide 81 .

[0080] On the other hand, when the processing unit 20, based on the above-mentioned determination result that the gamma-ray photons arriving at both the first detector 11 and the second detector 12 are photons arriving without Compton scattering in the subject, assumes that the pair of gamma-ray photons are photons arriving from the positron-emitting nuclide 83 in the subject 90, and based on the detection position and detection time of the gamma-ray photons obtained by the first detector 11 and the second detector 12 respectively, determines the position where the pair annihilation phenomenon occurred in the subject 90.

[0081] Then, after performing the above-described processing on the plurality of coincidence counting phenomena, the processing unit 20 creates a first tomographic image showing the distribution of Compton scattering positions in the subject 90 and creates a second tomographic image showing the distribution of annihilation event occurrence positions in the subject 90 .

[0082] The first tomographic image represents anatomical information of the subject 90. The second tomographic image represents the distribution of the positron-emitting nuclide 83 (distribution of the drug) in the subject 90, and can be used for diagnosis of the health status of the subject 90. The processing unit 20 can also obtain a second tomographic image in which the gamma-ray absorption distribution in the subject 90 is corrected by correcting the second tomographic image based on the first tomographic image.

[0083] In the second embodiment, in addition to achieving the same effects as the first embodiment, the Compton scattering position in the subject 90 and the position where the pair annihilation phenomenon occurs in the subject 90 can be obtained in a common period, thereby shortening the time for constraining the subject 90.

[0084] (Third Embodiment)

[0085] Figure 51 is a diagram showing the structure of an image acquisition device 1C according to the third embodiment. The image acquisition device 1C includes a measuring unit 10, a processing unit 20, and a display unit 30. The difference from the previous embodiments is that in the third embodiment, a positron emitting nuclide 81 is placed between the first detector 11 and the subject 90, and a positron emitting nuclide 82 is also placed between the second detector 12 and the subject 90. The positron emitting nuclide 81 and the positron emitting nuclide 82 are preferably of the same type as each other.

[0086] The processing unit 20 determines whether the gamma-ray photon arriving at the first detector 11 or the second detector 12 is Compton scattered, and whether the gamma-ray photon is generated in the positron-emitting nuclide 81 or the positron-emitting nuclide 82, based on at least one of the positions of the positron-emitting nuclide 81, 82, the energy of the gamma-ray photon, and the detection time of the gamma-ray photon obtained by the first detector 11 and the second detector 12. The processing unit 20 obtains the position where the gamma-ray photon is Compton scattered in the subject 90 based on the determination result.

[0087] In this embodiment, the positron emitting nuclides 81 and 82 can be arranged symmetrically with respect to the subject 90, so that a first tomographic image with better quality can be obtained. In addition, the number of Compton scattering phenomena per unit time in the subject 90 increases, so the measurement time can be shortened.

[0088] (Fourth Embodiment)

[0089] Figure 6 1 is a diagram showing the structure of an image acquisition device 1D according to a fourth embodiment. The image acquisition device 1D includes a measurement unit 10D, a processing unit 20, and a display unit 30. The image acquisition device 1D according to the fourth embodiment is different from the previous embodiments in that the measurement unit 10 is replaced with a measurement unit 10D.

[0090] The measuring unit 10D includes a first detector 11D and a second detector 12. The detection surface of the first detector 11D is narrower than the detection surface of the second detector 12. A positron emitting nuclide 81 is placed between the first detector 11D and the subject 90. The first detector 11D and the second detector 12 output signals indicating the detection position and the detection time respectively when a gamma ray photon is detected.

[0091] In order to obtain the first tomographic image, it is sufficient that one of a pair of gamma-ray photons generated by the electron / positron annihilation phenomenon in the positron-emitting nuclide 81 is incident on the first detector 11D and the other is incident on the subject 90 (or the region of interest in the subject 90). Therefore, as long as this condition is satisfied, the detection surface of the first detector 11D can be narrowed. The closer the position of the positron-emitting nuclide 81 is to the first detector 11D, the narrower the detection surface of the first detector 11D can be. In this way, the first detector 11D can be made small, so the image acquisition device 1D can be constructed at a low cost.

[0092] (Fifth Embodiment)

[0093] Figure 7 1 is a diagram showing a configuration of an image acquisition device 1E according to a fifth embodiment. The image acquisition device 1E includes a measurement unit 10E, a processing unit 20, and a display unit 30. The image acquisition device 1E according to the fifth embodiment is different from the previous embodiments in that a measurement unit 10E is provided instead of the measurement unit 10.

[0094] The measurement unit 10E includes a shielding body 13 in addition to the first detector 11 and the second detector 12. The shielding body 13 prevents gamma ray photons backscattered by one of the first detector 11 and the second detector 12 from entering the other.

[0095] The shielding body 13 is disposed between the first detector 11 and the second detector 12, that is, at a position that does not hinder the measurement of the Compton scattering position in the subject 90 and the measurement of the annihilation phenomenon occurrence position in the subject 90. The shielding body 13 is preferably a plate-shaped shielding body made of a high-density material (e.g., lead) that can shield gamma rays.

[0096] (Sixth Embodiment)

[0097] Figure 8 1 is a diagram showing the structure of an image acquisition device 1F according to the sixth embodiment. The image acquisition device 1F includes a measurement unit 10F, a processing unit 20, and a display unit 30. The image acquisition device 1F according to the sixth embodiment is different from the previous embodiments in that a measurement unit 10 is replaced with a measurement unit 10F.

[0098] The measuring unit 10F includes a moving unit 14 in addition to the first detector 11 and the second detector 12. The moving unit 14 moves the positron emitting nuclide 81 between the first detector 11 or the second detector 12 and the subject 90. The moving unit 14 can move the positron emitting nuclide 81 continuously as time passes, or can move the positron emitting nuclide 81 in a manner such that the positron emitting nuclide 81 is sequentially arranged at separate positions. The processing unit 20 always grasps the position of the positron emitting nuclide 81 in order to obtain the position where the gamma ray photon in the subject 90 is Compton scattered.

[0099] The moving direction of the positron emitting nuclide 81 may be one direction or two directions parallel to the detection surface of the first detector 11 or the second detector 12, may be a direction perpendicular to the detection surface, or may be three directions including a direction parallel to the detection surface and a direction perpendicular to the detection surface. By moving the positron emitting nuclide 81 in a direction parallel to the detection surface, the field of view of the device can be expanded or homogenized. By moving the positron emitting nuclide 81 in a direction perpendicular to the detection surface, the quality of the first tomographic image obtained can be improved.

[0100] Fig. 9 1F is a diagram for explaining changes in the field of view of the device when the positron emitting nuclide 81 is moved in a direction parallel to the detection surface of the first detector 11 in the measurement unit 10F of the image acquisition device 1F according to the sixth embodiment. In this figure, the field of view of the device is indicated by a shaded area. Fig. 9 As shown in (a) of FIG. 1 , when the positron emitting nuclide 81 is located near the center of the detection surface of the first detector 11 , both ends of the subject 90 may be out of the field of view.

[0101] In contrast, Fig. 9 As shown in (b), when the positron emitting nuclide 81 is located on the first end side of the detection surface of the first detector 11 (the side on the left side relative to the center in the figure), although the first end side of the subject 90 enters the field of view, the second end side of the subject 90 (the side on the right side relative to the center in the figure) sometimes deviates significantly from the field of view. On the contrary, when the positron emitting nuclide 81 is located on the second end side of the detection surface of the first detector 11, although the second end side of the subject 90 enters the field of view, the first end side of the subject 90 sometimes deviates significantly from the field of view. In this way, by moving the positron emitting nuclide 81 in a direction parallel to the detection surface of the first detector 11, the field of view of the device can be expanded or homogenized.

[0102] Fig.10This is a diagram for explaining the image quality of the first tomographic image when the positron emitting nuclide 81 is moved in the direction perpendicular to the detection surface of the first detector 11 in the measurement unit 10F of the image acquisition device 1F according to the sixth embodiment. In this figure, the position of the positron emitting nuclide 81 is set to P, the detection position of the gamma ray obtained by the first detector 11 is set to R1, the detection position of the gamma ray obtained by the second detector 12 is set to R2, and the position where the gamma ray is Compton scattered is set to C. The error range of the line segment connecting the position P and the position R1 and the error range of the line segment connecting the position P and the position C are indicated by the shaded areas.

[0103] Since there is an error based on spatial resolution in the detection position R1 of the gamma rays obtained by the actual first detector 11, an error occurs in the estimation of the line segment connecting position P and position R1, which in turn causes an error in the estimation of the line segment connecting position P and position C, and ultimately causes an error in the estimation of position C.

[0104] like Fig.10 As shown in (a), the longer the distance between position P and position C, the greater the estimated error of position C. Fig.10 As shown in (b), the shorter the distance between position P and position C, the smaller the estimation error of position C. Therefore, in order to improve the image quality of the first tomographic image to be obtained, it is preferable to place the positron emitting nuclide 81 at a position close to the subject 90.

[0105] Since the size and shape of the subject 90 vary, it is preferable to move the positron emitting nuclide 81 in three directions according to the size and shape of the subject 90 so as to expand or homogenize the field of view of the apparatus and improve the quality of the first tomographic image obtained.

[0106] (Simulation example)

[0107] Secondly, regarding the use Figure 1 and Figure 2 The conditions and results of the simulation performed to obtain the first tomographic image of the subject (an image showing the distribution of Compton scattering positions in the subject) are described. Here, Geant4 is used which can simulate the flight trajectory of particles in a substance using the Monte Carlo method.

[0108] Fig.11 The diagram shows the structure and arrangement of the measurement unit assumed in the simulation. The first detector 11 and the second detector 12 each include a 100×100×5 mm 3The time resolution and spatial resolution of gamma ray detection obtained by the first detector 11 and the second detector 12 are both set to an ideal 0. The first detector 11 and the second detector 12 are arranged opposite to each other in parallel and spaced apart by a distance of 90 mm.

[0109] A cylindrical model with a diameter of 30 mm and a height of 30 mm is assumed as the subject 90. The central axis of the cylinder of the subject 90 is made perpendicular to the detection surfaces of the first detector 11 and the second detector 12, and the subject 90 is placed at the center between the first detector 11 and the second detector 12. The positron emitting nuclide 81 is placed at the center between the first detector 11 and the subject 90. The size of the positron emitting nuclide 81 is ignored.

[0110] Fig.12 This is a diagram showing the structure of a model assumed as the subject 90 in the simulation. This figure is a diagram of the model of the subject 90 having a cylindrical shape observed in the central axis direction. The subject 90 has cylindrical regions 91, 92, 93, and 94 extending in a direction parallel to the central axis of the cylindrical shape, each with a diameter of 3 mm, and a cylindrical region 95 with a diameter of 30 mm covering these regions.

[0111] Region 91, region 92, region 93, and region 94 are provided in three portions. Region 91 is a region composed of iodine (atomic number 53). Region 92 is a region composed of air. Region 93 is a region composed of gadolinium (atomic number 64). Region 94 is a region composed of BGO as an example of a heavy substance. Region 95 is a region composed of water.

[0112] Fig.13 : is a diagram showing a first tomographic image obtained by simulation. This figure is an image of a cross section perpendicular to the central axis of a model of a subject 90 having a cylindrical shape. In this figure, the frequency of occurrence of Compton scattering is represented by shades, and the greater the frequency of occurrence of Compton scattering, the lighter the color. As shown in this figure, the first tomographic image obtained by simulation shows that the frequency of occurrence of Compton scattering becomes higher in the order of region 94 (BGO), region 93 (gadolinium), region 91 (iodine), region 95 (water), and region 92 (air).

[0113] In this way, it was confirmed that the first tomographic image ( Fig.13 ). The probability of Compton scattering in a substance is proportional to the atomic number of the substance. Therefore, it can be said that the first tomographic image represents the absorption coefficient μ of Compton scattering. Compton distribution.

[0114] The image acquisition device and the image acquisition method are not limited to the above-mentioned embodiments and configuration examples, and various modifications are possible. For example, the configurations of any two or more of the above-mentioned embodiments may be combined.

[0115] The image acquisition device according to the first mode of the above-mentioned embodiment comprises: (1) a measuring unit, which includes a first detector and a second detector each detecting a gamma-ray photon, and outputs a signal indicating a detection position and a detection time when the first detector and the second detector respectively detect a gamma-ray photon; and (2) a processing unit, which processes the signals respectively output from the first detector and the second detector; (3) the measuring unit, in a first measuring mode, places a subject between the first detector and the second detector, and places a positron-emitting nuclide between the first detector or the second detector and the subject, and outputs a signal indicating a detection position and a detection time of the gamma-ray photon respectively obtained by the first detector and the second detector; and (4) the processing unit, in the first measuring mode, processes the signals respectively output from the first detector and the second detector. In each simultaneous counting phenomenon in which a pair of gamma-ray photons generated by the annihilation phenomenon of electron / positron in a positron-emitting nuclide are simultaneously counted at the first detector and the second detector, it is assumed that the gamma-ray photons arriving at one of the first detector and the second detector are photons arriving without Compton scattering in the subject, and it is assumed that the gamma-ray photons arriving at the other detector are photons arriving after Compton scattering in the subject. Based on the detection position and detection time of the gamma-ray photons respectively obtained by the first detector and the second detector and the position of the positron-emitting nuclide, the position where the gamma-ray photons undergo Compton scattering in the subject is obtained, and a first tomographic image representing the distribution of the Compton scattering positions in the subject obtained for each of the multiple simultaneous counting phenomena is produced.

[0116] In the image acquisition device of the second mode, in the structure of the first mode, the measuring unit outputs a signal indicating the detection position and detection time of gamma ray photons respectively obtained by the first detector and the second detector in the second measurement mode when the subject to which the drug labeled with the positron emitting nuclide is administered is placed between the first detector and the second detector, and the processing unit calculates the position where the pair annihilation phenomenon occurs based on the detection position and detection time of the gamma ray photons respectively obtained by the first detector and the second detector for each simultaneous counting phenomenon in which the first detector and the second detector simultaneously count a pair of gamma ray photons generated by the pair annihilation phenomenon of electrons / positrons in the positron emitting nuclide, generates a second tomographic image indicating the distribution of the positions of the pair annihilation phenomena in the subject calculated for each of the plurality of simultaneous counting phenomena, and corrects the second tomographic image based on the first tomographic image.

[0117] According to the third mode of the above-mentioned embodiment, the image acquisition device comprises: (1) a measuring unit, which includes a first detector and a second detector each detecting a gamma-ray photon, and outputs a signal indicating a detection position and a detection time when the first detector and the second detector respectively detect a gamma-ray photon; and (2) a processing unit, which processes the signals respectively output from the first detector and the second detector; (3) when a subject to which a drug labeled with a positron-emitting nuclide is administered is placed between the first detector and the second detector, and a positron-emitting nuclide is placed between the first detector or the second detector and the subject, the measuring unit outputs a signal indicating a detection position and a detection time of the gamma-ray photon respectively obtained by the first detector and the second detector; and (4) a processing unit, for each simultaneous counting phenomenon in which the first detector and the second detector simultaneously count a pair of gamma-ray photons generated by the annihilation phenomenon of an electron / positron pair in the positron-emitting nuclide, (a) when a gamma-ray photon reaches one of the first detector and the second detector, (a) when one of the gamma-ray photons arriving at the first detector and the second detector is a photon arriving after Compton scattering in the subject, the position where the gamma-ray photon is Compton scattered in the subject is determined based on the detection position and detection time of the gamma-ray photons obtained by the first detector and the second detector, and the position of the positron-emitting nuclide placed between the first detector or the second detector and the subject; (b) when the gamma-ray photons arriving at both the first detector and the second detector are photons arriving without Compton scattering in the subject, the position where the pair annihilation phenomenon occurs is determined based on the detection position and detection time of the gamma-ray photons obtained by the first detector and the second detector; (c) a first tomographic image showing the distribution of the Compton scattering positions in the subject obtained for each of a plurality of simultaneous counting phenomena is prepared, a second tomographic image showing the distribution of the occurrence positions of the pair annihilation phenomenon in the subject obtained for each of a plurality of simultaneous counting phenomena is prepared, and the second tomographic image is corrected based on the first tomographic image.

[0118] In the image acquisition device of the fourth aspect, it can also be configured that, in the structure of the second or third aspect, the positron emitting nuclide placed between the first detector or the second detector and the subject and the positron emitting nuclide used to mark the drug administered to the subject are of the same type.

[0119] In the image acquisition device of the fifth mode, it can also be constructed that, in any structure of the first to fourth modes, the processing unit determines whether the gamma ray photons arriving at the first detector or the second detector have undergone Compton scattering based on any one or more of the position of the positron emitting nuclide, the energy of the gamma ray photons, and the detection time of the gamma ray photons obtained by the first detector and the second detector respectively.

[0120] In the image acquisition device of the sixth mode, it can also be constructed that, in any structure of the first to fifth modes, when the positron emitting nuclide is placed between the first detector and the subject, and the positron emitting nuclide is also placed between the second detector and the subject, the measuring unit outputs a signal indicating the detection position and detection time of the gamma ray photons obtained by the first detector and the second detector respectively.

[0121] In the image acquisition device of the seventh mode, it can also be constructed that, in any structure of the first to sixth modes, when the detection surface of the first detector is narrower than the detection surface of the second detector and a positron-emitting nuclide is placed between the first detector and the subject, the measuring unit outputs a signal indicating the detection position and detection time of the gamma ray photons obtained by the first detector and the second detector respectively.

[0122] In the image acquisition device of the eighth aspect, in any of the structures of the first to seventh aspects, the measurement unit may further include a shielding body that prevents gamma ray photons backscattered by one of the first detector and the second detector from entering the other.

[0123] In the image acquisition device of the ninth aspect, in any of the configurations of the first to eighth aspects, the measurement unit may further include a moving unit that moves the positron emitting nuclide between the first detector or the second detector and the subject.

[0124] The image acquisition method according to the first mode of the above-mentioned embodiment comprises: (1) a measuring step, which uses a first detector and a second detector each detecting a gamma-ray photon, and outputs a signal indicating a detection position and a detection time when the first detector and the second detector respectively detect a gamma-ray photon; and (2) a processing step, which processes the signals respectively output from the first detector and the second detector; (3) in the measuring step, in a first measuring mode, a subject is placed between the first detector and the second detector, and a positron-emitting nuclide is placed between the first detector or the second detector and the subject, and outputs a signal indicating a detection position and a detection time of the gamma-ray photon respectively obtained by the first detector and the second detector; and (4) in the processing step, in the first measuring mode For each simultaneous counting phenomenon in which the first detector and the second detector simultaneously count a pair of gamma-ray photons generated by the annihilation phenomenon of electron / positron in a positron-emitting nuclide, it is assumed that the gamma-ray photons arriving at one of the first detector and the second detector are photons arriving without Compton scattering in the subject, and it is assumed that the gamma-ray photons arriving at the other detector are photons arriving after Compton scattering in the subject, based on the detection position and detection time of the gamma-ray photons obtained by the first detector and the second detector respectively and the position of the positron-emitting nuclide, the position where the gamma-ray photons undergo Compton scattering in the subject is obtained, and a first tomographic image representing the distribution of the Compton scattering positions in the subject obtained for each of the multiple simultaneous counting phenomena is produced.

[0125] In the image acquisition method of the second mode, in the structure of the first mode, the measuring step outputs a signal indicating the detection position and detection time of the gamma ray photons respectively obtained by the first detector and the second detector in a state where the subject to which the drug labeled with the positron emitting nuclide is administered is placed between the first detector and the second detector in the second measuring mode, and the processing step calculates the position where the pair annihilation phenomenon occurs based on the detection position and detection time of the gamma ray photons respectively obtained by the first detector and the second detector for each simultaneous counting phenomenon in which the first detector and the second detector simultaneously count a pair of gamma ray photons generated by the pair annihilation phenomenon of electrons / positrons in the positron emitting nuclide, creates a second tomographic image indicating the distribution of the positions of the pair annihilation phenomena in the subject calculated for each of the plurality of simultaneous counting phenomena, and corrects the second tomographic image based on the first tomographic image.

[0126] According to the third mode of the above-mentioned embodiment, the image acquisition method comprises: (1) a measuring step, which uses a first detector and a second detector each detecting a gamma-ray photon, and outputs a signal indicating a detection position and a detection time when the first detector and the second detector respectively detect a gamma-ray photon; and (2) a processing step, which processes the signals respectively output from the first detector and the second detector, (3) when a subject to which a drug labeled with a positron-emitting nuclide is administered is placed between the first detector and the second detector, and a positron-emitting nuclide is placed between the first detector or the second detector and the subject, the measuring step outputs a signal indicating a detection position and a detection time of the gamma-ray photon respectively obtained by the first detector and the second detector, and (4) a processing step, for each simultaneous counting phenomenon in which the first detector and the second detector simultaneously count a pair of gamma-ray photons generated by the annihilation phenomenon of an electron / positron pair in the positron-emitting nuclide, (a) when a gamma-ray photon reaches one of the first detector and the second detector, (a) when the photons arriving at one end of the object are photons that do not undergo Compton scattering, and the gamma-ray photons arriving at the other end are photons that undergo Compton scattering, the position where the gamma-ray photons undergo Compton scattering in the object is determined based on the detection position and detection time of the gamma-ray photons obtained by the first detector and the second detector, and the position of the positron-emitting nuclide placed between the first detector or the second detector and the object; (b) when the gamma-ray photons arriving at both the first detector and the second detector are photons that do not undergo Compton scattering in the object, the position where the pair annihilation phenomenon occurs is determined based on the detection position and detection time of the gamma-ray photons obtained by the first detector and the second detector; (c) a first tomographic image showing the distribution of the Compton scattering positions in the object obtained for each of a plurality of simultaneous counting phenomena is produced, a second tomographic image showing the distribution of the occurrence positions of the pair annihilation phenomenon in the object obtained for each of a plurality of simultaneous counting phenomena is produced, and the second tomographic image is corrected based on the first tomographic image.

[0127] In the image acquisition method of the fourth aspect, in the structure of the second or third aspect, the positron emitting nuclide placed between the first detector or the second detector and the subject and the positron emitting nuclide marking the drug administered to the subject are of the same type.

[0128] In the image acquisition method of the fifth mode, it can also be constructed that, in any structure of the first to fourth modes, the processing step is based on any one of the position of the positron emitting nuclide, the energy of the gamma ray photon, and the detection time of the gamma ray photon obtained by the first detector and the second detector respectively, to determine whether the gamma ray photon arriving at the first detector or the second detector has undergone Compton scattering.

[0129] In the image acquisition method of the sixth mode, it can also be constructed that, in any structure of the first to fifth modes, when the positron emitting nuclide is placed between the first detector and the subject, and the positron emitting nuclide is also placed between the second detector and the subject, the measurement step outputs a signal indicating the detection position and detection time of the gamma ray photons obtained by the first detector and the second detector respectively.

[0130] In the image acquisition method of the seventh mode, it can also be constructed that, in any structure of the first to sixth modes, a detector with a narrower detection surface than the second detector is used as the first detector, and a positron emitting nuclide is placed between the first detector and the object, and the measurement step outputs a signal indicating the detection position and detection time of the gamma ray photons obtained by the first detector and the second detector respectively.

[0131] In the image acquisition method of the eighth aspect, in any of the configurations of the first to seventh aspects, the measuring step may prevent gamma ray photons backscattered by one of the first detector and the second detector from entering the other detector by the shielding body.

[0132] In the image acquisition method of a ninth aspect, in any of the configurations of the first to eighth aspects, the measuring step may move the positron emitting nuclide between the first detector or the second detector and the subject.

[0133] Industrial Applicability

[0134] The present invention can be used as an image acquisition device and an image acquisition method that can acquire a tomographic image representing anatomical information of a subject without performing image reconstruction processing.

[0135] Explanation of symbols

[0136] 1A to 1F: image acquisition device, 10, 10D, 10E, 10F: measuring unit, 11, 11D: first detector, 12: second detector, 13: shielding body, 14: moving unit, 20: processing unit, 30: display unit, 81, 82, 83: positron emitting nuclide, 90: object to be examined.

Claims

1. An image acquisition device, wherein: have: a measuring unit including a first detector and a second detector each detecting a gamma-ray photon, and outputting a signal indicating a detection position and a detection time when the first detector and the second detector respectively detect a gamma-ray photon; as well as a processing unit that processes the signals outputted from the first detector and the second detector, respectively; The measuring unit outputs a signal indicating a detection position and a detection time of a gamma ray photon obtained by the first detector and the second detector respectively in a first measuring mode, with a subject placed between the first detector and the second detector and a positron emitting nuclide placed between the first detector or the second detector and the subject. In the first measurement mode, the processing unit, for each simultaneous counting phenomenon in which the first detector and the second detector simultaneously count a pair of gamma-ray photons generated by the annihilation phenomenon of electron / positron in a positron-emitting nuclide, assumes that the gamma-ray photons arriving at one of the first detector and the second detector are photons arriving without Compton scattering in the subject, and assumes that the gamma-ray photons arriving at the other detector are photons arriving after Compton scattering in the subject, and calculates the position in the subject where Compton scattering of the gamma-ray photons occurs based on the detection position and detection time of the gamma-ray photons obtained by each of the first detector and the second detector and the position of the positron-emitting nuclide, and creates a first tomographic image representing the distribution of the Compton scattering positions in the subject calculated for each of the plurality of simultaneous counting phenomena.

2. The image acquisition device according to claim 1, wherein: In the second measurement mode, the measuring unit outputs a signal indicating a detection position and a detection time of a gamma ray photon obtained by the first detector and the second detector respectively, when the subject to which the drug labeled with a positron emitting nuclide is administered is placed between the first detector and the second detector. In the second measurement mode, the processing unit calculates the position where the pair annihilation phenomenon occurs based on the detection position and detection time of the gamma-ray photons obtained by the first detector and the second detector respectively for each simultaneous counting phenomenon in which the first detector and the second detector simultaneously count a pair of gamma-ray photons generated by the pair annihilation phenomenon of electron / positron in a positron-emitting nuclide, creates a second tomographic image representing the distribution of the positions where the pair annihilation phenomenon occurs in the subject calculated for each of the plurality of simultaneous counting phenomena, and corrects the second tomographic image based on the first tomographic image.

3. An image acquisition device, wherein: have: a measuring unit including a first detector and a second detector each detecting a gamma-ray photon, and outputting a signal indicating a detection position and a detection time when the first detector and the second detector respectively detect a gamma-ray photon; as well as a processing unit that processes the signals outputted from the first detector and the second detector, respectively; The measuring unit outputs a signal indicating a detection position and a detection time of a gamma-ray photon obtained by the first detector and the second detector respectively, when a subject to which a drug labeled with a positron-emitting nuclide is administered is placed between the first detector and the second detector, and when a positron-emitting nuclide is placed between the first detector or the second detector and the subject. The processing unit, For each simultaneous counting event in which the first detector and the second detector simultaneously count a pair of gamma-ray photons generated by an electron / positron pair annihilation event in a positron-emitting nuclide, In a case where the gamma-ray photons arriving at one of the first detector and the second detector are photons arriving without Compton scattering in the subject, and the gamma-ray photons arriving at the other detector are photons arriving after Compton scattering in the subject, the position where the gamma-ray photons are Compton scattered in the subject is determined based on the detection position and detection time of the gamma-ray photons obtained by the first detector and the second detector respectively, and the position of the positron-emitting nuclide placed between the first detector or the second detector and the subject. In the case where the gamma ray photons arriving at both the first detector and the second detector are photons arriving without Compton scattering in the subject, the position where the pair annihilation phenomenon occurs is determined based on the detection position and detection time of the gamma ray photons obtained by the first detector and the second detector respectively. A first tomographic image is produced showing the distribution of Compton scattering positions in the subject obtained for each of a plurality of simultaneous counting phenomena, a second tomographic image is produced showing the distribution of annihilation phenomenon occurrence positions in the subject obtained for each of a plurality of simultaneous counting phenomena, and the second tomographic image is corrected based on the first tomographic image.

4. The image acquisition device according to claim 2 or 3, wherein: The positron-emitting nuclide placed between the first detector or the second detector and the subject and the positron-emitting nuclide used to label a drug administered to the subject are of the same type.

5. The image acquisition device according to any one of claims 1 to 4, wherein: The processing unit determines whether the gamma ray photons arriving at the first detector or the second detector have undergone Compton scattering based on any one or more of the position of the positron emitting nuclide, the energy of the gamma ray photons, and the detection times of the gamma ray photons obtained by the first detector and the second detector respectively.

6. The image acquisition device according to any one of claims 1 to 5, wherein: The measuring unit outputs a signal indicating a detection position and a detection time of a gamma ray photon obtained by the first detector and the second detector respectively, when a positron emitting nuclide is placed between the first detector and the object and a positron emitting nuclide is also placed between the second detector and the object.

7. The image acquisition device according to any one of claims 1 to 6, wherein: The measuring unit outputs signals indicating detection positions and detection times of gamma-ray photons obtained by the first detector and the second detector, respectively, when the detection surface of the first detector is narrower than the detection surface of the second detector and a positron-emitting nuclide is placed between the first detector and the object.

8. The image acquisition device according to any one of claims 1 to 7, wherein: The measuring unit further includes a shielding body that prevents gamma ray photons backscattered by one of the first detector and the second detector from entering the other detector.

9. The image acquisition device according to any one of claims 1 to 8, wherein: The measuring unit further includes a moving unit that moves the positron-emitting nuclide between the first detector or the second detector and the object.

10. A method for obtaining an image, wherein: have: a measuring step, using a first detector and a second detector each detecting a gamma-ray photon, and outputting a signal indicating a detection position and a detection time when the first detector and the second detector respectively detect a gamma-ray photon; as well as a processing step of processing the signals outputted from the first detector and the second detector respectively, The measuring step includes, in a first measuring mode, placing a subject between the first detector and the second detector, and outputting signals indicating detection positions and detection times of gamma ray photons obtained by the first detector and the second detector respectively, in a state where a positron emitting nuclide is placed between the first detector or the second detector and the subject. The processing step is to, in the first measurement mode, for each simultaneous counting phenomenon in which the first detector and the second detector simultaneously count a pair of gamma-ray photons generated by the annihilation phenomenon of electron / positron pairs in a positron-emitting nuclide, assume that the gamma-ray photons arriving at one of the first detector and the second detector are photons that arrive without Compton scattering in the subject, and assume that the gamma-ray photons arriving at the other detector are photons that arrive after Compton scattering in the subject, and based on the detection position and detection time of the gamma-ray photons obtained by each of the first detector and the second detector and the position of the positron-emitting nuclide, the position where the gamma-ray photons undergo Compton scattering in the subject is obtained, and a first tomographic image representing the distribution of the Compton scattering positions in the subject obtained for each of the plurality of simultaneous counting phenomena is produced.

11. The image acquisition method according to claim 10, wherein: The measuring step outputs signals indicating detection positions and detection times of gamma ray photons obtained by the first detector and the second detector, respectively, in a second measuring mode, when the subject to which the drug labeled with a positron emitting nuclide is administered is placed between the first detector and the second detector. The processing step, in the second measurement mode, is to obtain, for each simultaneous counting phenomenon in which the first detector and the second detector simultaneously count a pair of gamma-ray photons generated by the pair annihilation phenomenon of electrons / positrons in a positron-emitting nuclide, determine the position where the pair annihilation phenomenon occurs based on the detection position and detection time of the gamma-ray photons obtained by the first detector and the second detector respectively, create a second tomographic image representing the distribution of the positions of the pair annihilation phenomena in the subject obtained for each of the plurality of simultaneous counting phenomena, and correct the second tomographic image based on the first tomographic image.

12. A method for obtaining an image, wherein: have: a measuring step, using a first detector and a second detector each detecting a gamma-ray photon, and outputting a signal indicating a detection position and a detection time when the first detector and the second detector respectively detect a gamma-ray photon; as well as a processing step of processing the signals outputted from the first detector and the second detector respectively, The measuring step outputs a signal indicating a detection position and a detection time of a gamma-ray photon obtained by each of the first detector and the second detector, when a subject to which a drug labeled with a positron-emitting nuclide is administered is placed between the first detector and the second detector, and when a positron-emitting nuclide is placed between the first detector or the second detector and the subject. The processing steps, For each simultaneous counting event in which the first detector and the second detector simultaneously count a pair of gamma-ray photons generated by an electron / positron pair annihilation event in a positron-emitting nuclide, In a case where the gamma-ray photons arriving at one of the first detector and the second detector are photons arriving without Compton scattering in the subject, and the gamma-ray photons arriving at the other detector are photons arriving after Compton scattering in the subject, the position where the gamma-ray photons are Compton scattered in the subject is determined based on the detection position and detection time of the gamma-ray photons obtained by the first detector and the second detector respectively, and the position of the positron-emitting nuclide placed between the first detector or the second detector and the subject. In the case where the gamma ray photons arriving at both the first detector and the second detector are photons arriving without Compton scattering in the subject, the position where the pair annihilation phenomenon occurs is determined based on the detection position and detection time of the gamma ray photons obtained by the first detector and the second detector respectively. A first tomographic image is produced showing the distribution of Compton scattering positions in the subject obtained for each of a plurality of simultaneous counting phenomena, a second tomographic image is produced showing the distribution of annihilation phenomenon occurrence positions in the subject obtained for each of a plurality of simultaneous counting phenomena, and the second tomographic image is corrected based on the first tomographic image.

13. The image acquisition method according to claim 11 or 12, wherein: The positron-emitting nuclide placed between the first detector or the second detector and the subject and the positron-emitting nuclide used to label a drug administered to the subject are of the same type.

14. The image acquisition method according to any one of claims 10 to 13, wherein: The processing step determines whether the gamma-ray photons arriving at the first detector or the second detector have undergone Compton scattering based on any one of the position of the positron-emitting nuclide, the energy of the gamma-ray photons, and the detection times of the gamma-ray photons obtained by the first detector and the second detector respectively.

15. The image acquisition method according to any one of claims 10 to 14, wherein: When the positron emitting nuclide is placed between the first detector and the object, and the positron emitting nuclide is also placed between the second detector and the object, the measuring step outputs a signal indicating the detection position and detection time of the gamma ray photons obtained by the first detector and the second detector respectively.

16. The image acquisition method according to any one of claims 10 to 15, wherein: When a detector having a narrower detection surface than that of the second detector is used as the first detector and a positron-emitting nuclide is placed between the first detector and the object, the measurement step outputs a signal indicating the detection position and detection time of the gamma-ray photons obtained by the first detector and the second detector respectively.

17. The image acquisition method according to any one of claims 10 to 16, wherein: In the measuring step, a shield is used to prevent gamma ray photons backscattered by one of the first detector and the second detector from entering the other detector.

18. The image acquisition method according to any one of claims 10 to 17, wherein: The measuring step moves the positron-emitting nuclide between the first detector or the second detector and the object.

Images