JP2008232971A - Nuclear medicine diagnostic apparatus and photon measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nuclear medicine diagnostic apparatus capable of detecting gamma rays having a wide range of energy. <P>SOLUTION: The apparatus includes a Compton camera having a front detector filled with a gas and detecting information on a charged particle generated by Compton scattering in the gas and a rear detector detecting information on the scattered photon. The apparatus is constituted by laminating a plurality of front detectors having different gas kinds. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a nuclear medicine diagnostic apparatus, which administers a radioactive substance into the body of a subject, captures gamma rays and the like that accumulate and emit at a specific site, and images a lesion position and the like, and The present invention relates to a photon measuring apparatus suitable for use in a nuclear medicine diagnostic apparatus such as a Compton camera.

  This type of nuclear medicine diagnostic apparatus includes a Compton camera, detects a gamma ray emitted from the subject by the Compton camera, and calculates an incident direction of the gamma ray and the like, thereby obtaining an image of the radioactive substance in the subject. We are trying to make it.

  The gamma rays from the subject cause so-called Compton scattering with electrons in the Compton camera. That is, a part of the energy of the gamma ray is given to the electrons to be blown off, and the gamma rays themselves lose the energy given to the electrons and scatter as scattered gamma rays (scattered photons). Then, the bounced electrons (recoil electrons: charged particles) jump while ionizing surrounding molecules, and at that time, electrons and ions are generated.

  Information on the tracks of the electrons (drift electrons) is detected by a pre-stage detector called a so-called track detector, and information on the scattering direction and energy of the scattered gamma rays is detected by a post-stage detector called a so-called scattered gamma ray detector. Is to be detected.

  Then, at least a gamma ray incident direction or the like is calculated based on information from the former detector and the latter detector, and based on this, the radioactive substance in the subject is imaged.

  The former detector is configured to have a space filled with a specific kind of gas. This is to efficiently cause Compton scattering to the incident gamma rays.

  Details of the Compton camera having such a configuration are disclosed in, for example, Patent Document 1 below.

  Such a Compton camera is an apparatus that images the radiation source by measuring the X-rays or gamma rays generated by using Compton scattering of the radiation from the radiation source or generation of electron-positron pairs.

  The nuclear medicine diagnostic apparatus equipped with a Compton camera does not need to select the type of radioisotope when compared with, for example, a positron emission tomography (PET) apparatus, and also includes a gamma camera and a single photon emission CT (SPECT) apparatus. When compared with the above, there is an advantage that a configuration that does not require a mechanical collimator can be obtained.

Details of such a Compton camera are disclosed in, for example, Patent Document 2 below.
JP 2001-13251 A JP-A 63-158490

  However, the energy of gamma rays to be detected by the Compton camera disclosed in Patent Document 1 differs depending on the radioactive substance that is the gamma ray source.

  For example, the gamma ray energy of a radiopharmaceutical used for a nuclide of a positron emission tomography (PET) apparatus is 511 keV, and the gamma ray energy of a radiopharmaceutical (for example, technesium) used for a nuclide of a single photon emission CT (SPECT) apparatus is 140 keV.

  In this case, depending on the magnitude of the energy of these gamma rays and the type of gas charged in the front stage detector of the Compton camera of Patent Document 1, it greatly affects the establishment of Compton scattering and the like, and the specific accuracy of the incident direction of gamma rays is increased. Will have an impact.

  This means that the Compton camera is suitable for detecting gamma rays in a specific energy range, regardless of what kind of gas is filled in the upstream detector. And the nuclear medicine diagnostic apparatus provided with a Compton camera like patent document 1 will restrict | limit the nuclide administered to a subject.

  Further, the Compton camera of Patent Document 2 is a pre-stage detector that detects the position information at the first Compton scattering point and the information on the momentum of recoil electrons generated by the Compton scattering by Compton scattering gamma rays emitted from the subject. And a post-stage detector for detecting information related to gamma rays scattered by the Compton scattering, these detectors are arranged close to each other and their positional relationship is always fixed. It was what was done.

  And the Compton camera like patent document 2 was requested | required that a still higher-definition image could be obtained, when an image was reconfigure | reconstructed with the detection signal.

  Compton cameras are known to detect X-rays and gamma rays for astronomical observation in addition to nuclear medicine diagnostic equipment. In this case, the Compton camera also has its front and rear detectors close to each other. As well as being arranged, their positional relationship is always fixed.

  An object of the present invention is to provide a nuclear medicine diagnostic apparatus capable of detecting gamma rays having a wide range of energy.

  Another object of the present invention is to provide a photon measuring apparatus capable of obtaining a high-definition image.

   The outline of a representative one of the nuclear medicine diagnosis apparatuses according to the invention disclosed in the present application will be briefly described as follows.

(1) The nuclear medicine diagnostic apparatus according to the present invention includes, for example, a front-stage detector that detects information of charged particles that are filled with gas and is generated by Compton scattering in the gas, and a rear-stage detector that detects information of scattered photons. With a Compton camera,
It is characterized in that a plurality of the former detectors having different types of gas are stacked.

(2) The nuclear medicine diagnostic apparatus according to the present invention includes, for example, a front-stage detector that detects information of charged particles that are filled with a gas and is generated by Compton scattering in the gas, and a rear-stage detector that detects information of scattered photons. With a Compton camera,
It is characterized in that the upstream detectors having different types of gas are arranged in parallel in a plurality of planes.

  Moreover, it will be as follows if the outline | summary of a typical thing is demonstrated easily among the photon measuring devices based on the invention disclosed in this application.

(1) A photon measuring device according to the present invention includes, for example, a front-end detector that reacts with a photon emitted from a subject and detects position information at a first reaction point and information on momentum of charged particles generated by the reaction;
A post-stage detector that detects information about the charged particles or photons scattered by the reaction, mechanically separated from the pre-stage detector;
Image reconstruction means for imaging the photon source in the subject from each information from the front detector and the rear detector;
It is characterized in that adjustment means capable of varying the distance between the front detector and the rear detector is provided.

(2) The photon measuring device according to the present invention is characterized in that, for example, on the premise of the configuration of (1), a mechanism is provided in which the former detector is brought close to or in close contact with a subject.

(3) The photon measuring apparatus according to the present invention is provided with a mechanism for rotating around the subject in a state where the front detector is forwardly oriented with the rear detector, for example, on the premise of the configuration of (1). And

(4) The photon measuring apparatus according to the present invention is provided with a mechanism for rotating around the subject in a state where the rear detector is forwardly directed to the front detector, for example, on the premise of the configuration of (1). And

(5) The photon measuring apparatus according to the present invention is characterized in that, for example, the configuration of (3) is premised, and the post-stage detector is configured by an annular body surrounding the subject.

(6) The photon measuring apparatus according to the present invention is characterized in that, for example, the configuration of (3) is premised, and the pre-stage detector is configured by an annular body surrounding the subject.

  In addition, this invention is not limited to the above structure, A various change is possible in the range which does not deviate from the technical idea of this invention.

  The nuclear medicine diagnosis apparatus configured as described above can detect gamma rays having a wide range of energy.

  In addition, the photon measuring apparatus configured as described above can obtain a high-definition image.

  FIG. 1 is a block diagram showing a nuclear medicine diagnosis apparatus according to the present invention, and is a block diagram showing an embodiment of a Compton camera provided therein.

  In FIG. 1, the Compton camera 1 includes a first front-stage detector 10 and a second front-stage detector 20 that are track detectors, for example, in two stages (two layers), and the first front-stage detector 10 and the second front-stage detector 10. It comprises a detector 20 and a post-stage detector 30 serving as a scattered gamma ray detector.

  In the figure, a subject to be diagnosed (not shown) is positioned on the first pre-stage detector 10 side of the Compton camera 1, and incident gamma rays 2 from the radiopharmaceutical administered into the subject are in the first pre-stage. It is directed and emitted toward the detector 10 side.

  In the first front detector 10, the gas package 10A and the detector 10B are sequentially arranged on the incident direction side of the incident gamma ray 2, and the second front detector 20 is also sequentially arranged on the incident direction side of the incident gamma ray 2 in the gas package 20A and detector 20B. Is arranged.

  In the first pre-stage detector 10 and the second pre-stage detector 20, the gas packages 10A and 20A and the detectors 10B and 20B have the same configuration, for example, but the gas of the first pre-stage detector 10 is the same. For example, the package 10A is filled with, for example, an argon-based gas, and the gas package 20A of the second upstream detector 20 is filled with a xenon-based gas.

  The first pre-stage detector 10 and the second pre-stage detector 20 are filled with gas. The first pre-stage detector 10 further passes through the first pre-stage detector 10 and enters the second pre-stage detector 20. This is to increase the probability of causing the incident gamma ray 2 to cause Compton scattering in the gas space, thereby efficiently detecting the gamma ray. Further, these gases are sealed at a high pressure, for example, thereby increasing the electron density of the gas and improving the probability of occurrence of Compton scattering.

  The argon-based gas filled in the gas package 10A of the first front-stage detector 10 is composed of a relatively light element, and the incident gamma ray 2 incident on the first front-stage detector 10 has a relatively low energy of about 200 keV, for example. The first pre-detector 10 is suitable for measuring the incident gamma ray 2. FIG. 1 shows that incident gamma rays 2 are incident on the first front-stage detector 10 and scattered gamma rays 3 and recoil electrons 4 are generated by Compton scattering generated in the gas package 10A. Information regarding the scattered gamma rays 3 is detected by the post-stage detector 30, and information regarding the recoil electrons 4 is detected by the detector 10B of the first pre-stage detector 10. Details thereof will be described later.

  In this case, when the incident gamma ray 2 incident on the second pre-stage detector 10 has a relatively high energy, for example, about 700 keV, the Compton scattered electrons by the gamma ray are filled with an argon-based gas. The probability of penetrating through the gas package 10A increases. This is the same even when the pressure of the argon-based gas is increased.

  The Zenon gas filled in the gas package 20A of the second front detector 20 is composed of a relatively heavy element, and is incident gamma rays 2 (for example, about 700 keV, which are incident through the first front detector 10 and are relatively input. The second pre-stage detector 20 is configured as suitable for measuring (having high energy). In FIG. 2 drawn corresponding to FIG. 1, the incident gamma ray 2 is incident from the first front-stage detector 10 to the second front-stage detector 20, and the Compton generated in the gas package 20 </ b> A. It shows that scattered gamma rays 3 and recoil electrons 4 are generated by the scattering. Information about the scattered gamma rays 3 is detected by the post-stage detector 30, and information about the recoil electrons 4 is detected by the detector 20 </ b> B of the second pre-stage detector 20.

  In general, a relatively heavy gas such as a Zenon-based gas has a larger influence of so-called Doppler broadening than an argon-based gas, for example, and the linearity of recoil electrons 4 is reduced, leading to a decrease in resolution. As described above, the second pre-stage detector 20 uses a relatively heavy gas such as a Zenon system and makes the incident gamma ray 2 having a relatively high energy to be detected, thereby reducing the influence of the Doppler broadening. Have

  In the embodiment described above, the first-stage detector 10 and the second second-stage detector 20 constitute a front-stage detector. However, the present invention is not limited to the above two preceding detectors, and three or more preceding detectors may be prepared and configured in multiple stages (multilayers). In this case, the gas to be filled in each pre-stage detector may be different in each pre-stage detector, and the type thereof is not limited to the argon-based gas or the Zenon-based gas.

  By configuring in this way, the pre-stage detector (configured by a plurality of multi-stage pre-stage detectors) can cope with detection of incident gamma rays from low energy to high energy. A Compton camera equipped with can handle incident gamma rays with a wide range of energy.

  FIG. 3 is a plan view showing an embodiment of the detector 10B of the first front detector 10 and the detector 20B of the second front detector 20 of the Compton camera 1 shown in FIGS. For this reason, the detector 10B and the detector 20B shown in FIGS. 1 and 2 (and also FIGS. 5 and 6) are simply drawn.

  In FIG. 3, for example, a plurality of strip-like cathodes 12 extending in the y direction are formed in parallel on the surface of the semiconductor substrate 11 in the x direction. Here, the y direction and the x direction are, for example, directions orthogonal to each other.

  Each of these cathodes 12 is formed with, for example, a plurality of circular through holes 13 arranged at the same pitch along the extending direction.

  The through holes 13 formed in each cathode 12 are arranged in a matrix, and the n (1, 2, 3,...) Th through hole 13 from one end of each cathode 12 is one of the other cathodes. The n-th through-hole from the end of the X-axis is aligned with the x-direction axis.

  An anode 14 having a diameter smaller than the diameter of the through hole 13 is formed on the surface of the semiconductor substrate 11 and at the center of each through hole 13 formed in each cathode 12. Each of these anodes 14 is electrically connected to a wiring layer 15 formed on the back surface of the semiconductor substrate 11 through a through hole (not shown) formed in the semiconductor substrate 11.

  The wiring layer 15 has a strip shape extending in the x direction on the back surface of the semiconductor substrate 11 and is formed in parallel in the y direction.

  The anodes 14 disposed in the nth through-hole 13 from one end of each cathode 12 are connected to the wiring layer 15 disposed nth from the one end, respectively.

  The detectors 10B and 20B configured as described above are pixels (3 × 4 in FIG. 3) that are regions that are arranged around the anodes 14 on the detection surface in the plane and that are defined as other adjacent regions. In other words, a signal is output from the cathode 12 and the wiring layer 15 crossing the pixel on which the recoil electrons 4 are incident, and position information of the recoil electrons 4 is obtained. It is like that.

  Here, the cathode 12, the anode 14, and the wiring layer 15 are formed by a selective etching method using a so-called photolithography technique, and each of the anodes 14 arranged in a matrix form is adjacent to each other in the x direction and the y direction. The gap between the anode 14 and the anode 14 is about 400 μm. Thereby, tracks of recoil electrons 4 (charged particles) can be measured at submillimeter intervals.

  The detailed functions and effects of the detectors 10B and 20B are described in, for example, A new design of the gaseous imaging detector: Micro Pixel Chamber, Atsuhiko Ochi et al., Nuclear Instruments and Methods in Physics Research A 471 (2001). It is described in documents such as 264/267.

  The energy of the recoil electrons 4 is several tens to several hundreds keV and can fly only about several centimeters even in the gas. Therefore, it is necessary to measure the tracks of the recoil electrons 4 at submillimeter intervals. And the Compton camera 1 shown in FIG. 2 is the structure which satisfy | filled such a request | requirement.

  Originally, in order to obtain a gamma ray image by the Compton camera 1, it is necessary to know the incident direction of the incident gamma ray 2 to the Compton camera 1, and if this incident direction is known, a large amount of noise gamma rays other than the measurement target can be easily removed. It is possible to image even single gamma-ray nuclides with high energy range.

  In order to know the incident direction of the gamma ray 2, the direction and energy of the recoil electrons 4 and the scattered gamma ray 3 generated in the process in which the gamma ray 2 scatters with electrons in the substance (Compton scattering) as quanta are measured. Must be configured.

  FIG. 4 is a configuration diagram schematically showing one embodiment of a nuclear medicine diagnosis apparatus including the above-described Compton camera 1.

  The Compton camera 1 includes a front-stage detector and a rear-stage detector 30 each including a first front-stage detector 10 and a second front-stage detector 20.

  The incident gamma ray 2 incident on the first pre-stage detector 10 is Compton scattered with electrons in the substance at the Compton scattering point CSP, and the recoil electrons 4 are captured by the first pre-stage detector 10, for example. The first pre-stage detector 10 measures the position of the Compton scattering point CSP and the energy of the recoil electrons 4.

  In this case, the energy of the recoil electrons 4 is usually extremely small, such as several tens to several hundreds keV. For this reason, although the conventional Compton camera can measure the position information of the Compton scattering point CSP and the energy of the recoil electrons 4, it is difficult to measure the recoil direction of the recoil electrons 4. According to the Compton camera 1 of the present embodiment including the detector 10B (10A) shown in FIG. 3, the recoil direction of the recoil electrons 4 can be measured. The reason for this will be described later.

  On the other hand, the scattered gamma ray 3 is incident on the post-stage detector 30, and its energy and direction are measured by the post-stage detector 30.

  In the case of the incident gamma ray 2 penetrating the first pre-stage detector 10, the above-described operation is also performed in the second pre-stage detector 20. The second pre-stage detector 20 detects the position information of the Compton scattering point and the recoil electrons 4. Measurements of energy and recoil direction are made.

  Each measurement information obtained by the first pre-stage detector 10, the second pre-stage detector 20, and the post-stage detector 30 is collected by an information collecting device 41, and at least the elevation angle of the incident gamma ray 2 with respect to the direction of the scattered gamma ray, and the incident gamma ray The direction of 2 is calculated.

  Here, to calculate the direction of the incident gamma ray 2, it is necessary to determine the azimuth angle of the incident gamma ray 2 with respect to the direction of the scattered gamma ray 3, and this azimuth angle is a physical quantity determined by the direction of the recoil electrons 4. It has become. In the conventional Compton camera, since it was difficult to obtain the direction of the recoil electrons 4 as described above, the incident direction of the incident gamma ray 2 could be determined only within the range of the cone (surface) CN shown in FIG. According to the Compton camera 1 of this embodiment capable of measuring the recoil direction of the recoil electrons 4, the range can be greatly narrowed. The reason for this will also be described later.

  Then, image reconstruction is performed by the image reconstruction device 42 based on the calculation information by the information collecting device 41, and the image is displayed on the display device 43.

  FIG. 5 is an explanatory diagram showing the reason why the front detector 10 or 20 in the Compton camera 1 can obtain information on the direction of the recoil electrons 4. In FIG. 5, only one of the first front-stage detector 10 and the second front-stage detector 20 is shown. This is because the first pre-stage detector 10 and the second pre-stage detector 20 perform the same operation.

  In FIG. 5, in the process in which the recoil electrons 4 scattered by Compton scattering fly in the gas of the former detector 10 (20), the gas molecules of the gas are ionized to generate new drift electrons. .

  The drift electrons are sequentially generated along the trajectory 5 of the recoil electrons 4 and fall on the detection surface of the detector 10B (20B).

  Each dropped drift electron is detected in a different pixel on the detection surface of the detector 10B (20B), and the track of the recoil electron 4 can be associated with the position of the pixel.

  As described above, since the detector 10B (20B) is configured to be extremely finely processed, the pixels are also finely formed, and the tracks of the recoil electrons 4 can be detected with high accuracy. .

  In this way, the direction of the recoil electrons 4 can be detected, and the azimuth angle of the incident gamma rays 2 with respect to the direction of the scattered gamma rays 3 can be detected.

  In the drawing, a post-stage detector 30 is arranged around the pre-stage detector 10 (20) (only the lower part of the pre-stage detector 10 (20) is shown in FIG. 5). The direction or the like is detected. Since the azimuth angle of the incident gamma ray 2 can be detected in this manner, the incident direction of the incident gamma ray 2 can be uniquely determined.

  In addition, the angle formed between the recoil electrons 4 and the scattered gamma rays 2 can be calculated. By calculating this angle, the incident direction of the incident gamma rays 2 can be specified in a very narrow range. FIG. 5 shows the range of the base point (end opposite to the arrow) of the incident gamma ray 2 as a part of a circle (arc) CP, and indicates that the range of the incident direction is narrowed.

  FIG. 6 is a block diagram showing another embodiment of the Compton camera 1 provided in the nuclear medicine diagnostic apparatus according to the present invention. Portions showing the same members as those of the Compton camera 1 shown in FIG.

  1 is different from the case of FIG. 1 in that the first front-stage detector 10 and the second front-stage detector 20 are arranged side by side in a plane. The first upstream detection unit 10 includes a gas package 10A and a detector 10B, and the gas package 10A is filled with, for example, an argon-based gas. The second upstream detection unit 20 includes a gas package 20A. The gas package 20A is configured to be filled with, for example, a Zenon-based gas.

  In this case, since the rear detection unit 30 cannot be formed in common with the first front detection unit 10 and the second front detection unit 20 as in the case of FIG. 1, the first front detection unit 10 and the second front detection unit. 20 is provided so as to correspond to 20 respectively. That is, a post-stage detector 30 (shown in FIG. 30A) for the first pre-stage detector 10 is provided, and a post-stage detector 30 (shown in 30B in the figure) for the second pre-stage detector 20 is provided. In this case, the rear detection unit 30A and the rear detection unit 30B may be formed separately or integrally.

  Even in such a configuration, the first pre-stage detector 10 and the post-stage detector 30A can detect gamma rays having relatively low energy, and the second pre-stage detector 20 and the post-stage detector 30B are relatively Gamma rays with high energy can be detected. Therefore, it is possible to obtain a nuclear medicine diagnostic apparatus that can detect gamma rays having a wide range of energy.

  In the above-described embodiment, the number of front-stage detectors arranged side by side is not limited to two, but may be three or more, and the gas filled in the gas package of the nuclear front-stage detector is the above-mentioned. It is not limited to the kind of gas, but it may be different from each other.

  Each of the embodiments described above may be used alone or in combination. This is because the effects of the respective embodiments can be achieved independently or synergistically.

  Next, as an embodiment of the photon measuring apparatus according to the present invention, a photon is shown in which a photon emitted from a subject causes Compton scattering by a front detector, and a scattered photon generated by the Compton scattering is absorbed by the post detector. A case where the camera is applied to a nuclear medicine diagnostic apparatus will be described with reference to FIG.

  In FIG. 7, first, a subject (subject) 50 is lying on the side facing the photon measuring device 60.

  A radiopharmaceutical is administered to the subject 50, and photons (incident gamma rays) 51 are emitted radially from the radiopharmaceutical (radiation source) to the photon measuring device 60. Radiopharmaceuticals, for example, have the property of being specifically accumulated by active metabolism of cancer cells when administered to a subject suffering from cancer, or the blood flow rate when administered to a subject suffering from infarction. Some have the property of accumulating accordingly.

  The photon measuring device 60 has a pre-stage detector 61 for allowing the photon 51 emitted from the subject 50 to enter. In the upstream detector 61, the first Compton scattering (reaction) is caused by the incidence of the photon 51, and the scattered photon (charged particle) 52 is scattered from the Compton scattering point A to the downstream detector 62 described later and recoiled. Electrons e are generated. The upstream detector 61 detects position information of the Compton scattering point A and information on the momentum of the recoil electrons e, and the detection signal is input to the information collecting device 63.

  Further, a rear detector 62 is disposed in the forward direction with respect to the front detector 61, and the scattered photons 52 are incident on the rear detector 62. The post-stage detector 62 detects information related to the momentum of the scattered photons 52, and the detection signal is input to the information collecting device 63. In this specification, the front detector 61 and the rear detector 62 are sequentially arranged in front of the subject 50, and the arrangement relationship between the front detector 61 and the rear detector 62 is as described above. It is expressed as “proactive”.

  The information collecting device 63 integrates the detection signal from the upstream detector 61 and the detection signal from the downstream detector 62, and sends the integrated signals to the image reconstruction device 64. An image relating to the radiation source reconstructed by 64 is displayed on the display device 65.

  Further, the upstream detector 61 has a mechanism for adjusting the geometric arrangement of the upstream detector 61, and at least the upstream detector 61 can change the separation distance along the incident direction of the photon 51 with respect to the subject 50. A position adjusting mechanism 66 that can adjust the position in the (α direction in the figure) is provided.

  Further, the post-stage detector 62 has a mechanism for adjusting the geometric arrangement of the post-stage detector 62, and at least the post-stage detector 62 has a variable separation distance along the incident direction of the scattered photon 52 with respect to the pre-stage detector 61. A position adjusting mechanism 67 capable of adjusting the position in the direction (β direction in the figure) is provided.

  The position adjustment mechanism 66 can adjust the position of the front detector 61 in the α direction in the figure, and the position adjustment mechanism 67 can change the position of the rear detector 62 in the β direction in the figure. Thus, the distance L between the front-stage detector 61 and the rear-stage detector 62 that are mechanically separated from each other can be varied.

  By changing the distance L between the upstream detector 61 and the downstream detector 62, the image quality of the image displayed on the display device 65 changes, and it is possible to set the image quality convenient for the operator. Generally, if the distance L between the front detector 61 and the rear detector 62 is increased, the image quality is improved accordingly, and so-called blur display is suppressed.

  Here, the reason why the image quality is improved when the distance L between the front detector 61 and the rear detector 62 is increased will be considered below.

  First, FIG. 8A shows that the front detector 61 and the rear detector 62 are arranged with a distance L, for example. Note that the upstream detector 61 and the downstream detector 62 shown in FIG. 8A are upside down unlike the case of FIG. 7, and the subject 50 (not shown) is the upper side in the figure. Please consider that it is positioned.

  In the figure, a photon 51 incident on a front detector 61 from a radiation source S in a subject is scattered at a Compton scattering point A, then becomes a scattered photon 52 and enters a rear detector 62 and is absorbed at an absorption point B. Has been. However, when the position resolution of the front detector 61 and the rear detector 62 is taken into consideration, the photon 51 ′ incident on the front detector 61 from the radiation source S ′ in the subject is scattered after being scattered at the Compton scattering point A ′. As a result, the photon 52 ′ is incident on the post-stage detector 62 and absorbed at the absorption point B ′. The scattered photon 52 (52 ') is scattered with a Compton scattering angle θ with respect to the photon 51 (51').

Therefore, photon measuring device 60, the position resolution of the front detector 61 and the rear stage detector 62, an angle resolution delta _Shitaganma against scattered photons 52, also angular resolution with respect to the incident photon 51 delta _.theta.0 Will have.

Then, the photon measuring device 60, since the direction of the incident photon 51 on the basis of the direction of the scattered photons 52 is calculated (determined), as long resulting angular resolution delta _Shitaganma is a small value, small angular resolution delta _.theta.0 value Measurement accuracy can be improved.

FIG. 8B is a diagram showing the portions of scattered photons 52 and 52 ′ that determine the angular resolution _Δθγ . In the figure, the upper diagram shows the _relationship between the front detector 61 and the rear detector 62. The distance L ′ between them is relatively small,
The lower diagram shows that the distance L ″ between the front detector 61 and the rear detector 62 is relatively large. These diagrams show the Compton scattering points A and A ′ and the scattered photon absorption point B. , B ′ are shown in the same position in order to make the conditions the same.

  FIG. 8C shows a vector of scattered photons 52 and 52 ′, and in the upper diagram, the distance L ′ between the front detector 61 and the rear detector 62 is relatively small. The lower diagram corresponds to the case where the distance L ″ between the front detector 61 and the rear detector 62 is relatively large. Compton scattering points A and A ′ as base points are shown in a matched manner.

In this case, the angular resolution _Δθ ″ _γ when the distance L ″ between the front detector 61 and the rear detector 62 is relatively large at the angular resolution _Δθγ that is the opening angle of each vector. It is clear that the angle resolution _Δθ′γ is smaller when the distance L ′ between the upstream detector 61 and the downstream detector 62 is relatively small. The image quality can be improved by increasing the distance L between 61 and the rear detector 62.

  In the configuration shown in FIG. 7, when the distance between the front detector 61 and the rear detector 62 is set to a relatively large distance LL as shown in FIG. 9A, the angular resolution in the scattered photon 52 is improved. The image quality of the radiation source in the display device 65 can be improved. Also, as shown in FIG. 9B, when the distance between the front detector 61 and the rear detector 62 is set to a relatively small distance LS, the detection efficiency of the scattered photons 52, so-called sensitivity, is improved, and the display device 65 The image regarding the radiation source can be imaged in a short time.

  Further, with the configuration shown in FIG. 7, the pre-stage detector 61 can be arranged close to or in close contact with the subject 50. Thereby, the distance between the subject 50 and the Compton scattering point A can be made extremely small, and the spatial resolution of the photon measuring device 60 can be improved. Since the solid angle between the subject 50 and the photon measuring device 60 can be increased and the geometric detection efficiency can be improved, the imaging time can be shortened and the image quality can be improved.

  In this case, in a state where the front-stage detector 61 is disposed close to or in close contact with the subject 50, the distance L between the rear-stage detector 62 with respect to the front-stage detector 61 is varied, thereby detecting spatial resolution and detection. Adjustment that takes both efficiency into account can be achieved, and shooting corresponding to the situation of the subject 50 or the purpose of shooting can be performed.

  For example, as shown in FIG. 9C, when the front detector 61 and the rear detector 62 are configured to be adjusted to a relative three-dimensional arrangement, depending on the energy level of the incident photon 51 The front detector 61 and the rear detector 62 can be arranged at appropriate positions. That is, in the case shown in FIG. 9C, unlike the case of FIG. 9D drawn correspondingly, the forward scattered scattered photons 52 can be selectively acquired, and a highly accurate event can be obtained with high statistics. As a result, blurring of the image can be suppressed and high image quality can be obtained. The reason for this is that the number of scattering events in the front detector 61 is generally larger than the number of scattering events in the rear detector 62, and the incident photons from the energy dependence of the energy resolution of the front detector 61 and the rear detector 62. This is because the direction determination accuracy of 51 is higher in the forward scattering event.

  FIG. 10 is a block diagram showing another embodiment of the photon measuring apparatus according to the present invention. 10, the information collection device 63, the image reconstruction device 64, and the display device 65 shown in FIG. 7 are omitted.

  In FIG. 10, for example, a front detector 61 and a rear detector 62 are sequentially arranged in front of the subject 50. For example, the front detector 61 and the rear detector 62 are separated from each other by a distance L in the illustrated state.

  The front detector 61 is moved by the position adjusting mechanism 66 along the trajectory 21O indicated by the dotted line in the drawing. In this case, the detection surface of the pre-stage detector 61 facing the subject 50 moves as it is facing the subject 50, and as a result, moves while rotating on the orbit.

  Further, the post-stage detector 62 is also moved by the position adjusting mechanism 67 along the trajectory 22O indicated by the dotted line in the drawing. Also in this case, the detection surface of the rear detector 62 facing the subject 50 moves as it is facing the subject 50, for example, and as a result, moves while rotating on the orbit.

  In the above-described movement of the upstream detector 61 and the downstream detector 62, the upstream detector 61 and the downstream detector 62 remain opposed to each other. However, the upstream detector 61 and the downstream detector 62 have the distance L. The interval may be maintained as it is or may be varied by adjustment.

  The photon measuring apparatus configured as described above is configured to perform imaging while rotating the detector including the front detector 61 and the rear detector 62 around the subject 50. Therefore, each image can be taken from a plurality of directions, and the count of photons to be measured can be increased. This has the effect of reducing image quality degradation caused by statistical errors. Then, isotropic data necessary for obtaining a high-definition three-dimensional image can be collected.

  The post-stage detector 62 arranged on the outer side with respect to the pre-stage detector 61 by being separated by a distance L can make the movement locus 22O a simple circular orbit, that is, the distance from the subject is constant. be able to. As a result, the image reconstruction calculation in the image reconstruction device 64 can be simplified, and as a result, high-speed data processing can be achieved.

  Furthermore, with the above-described configuration, the effective area on the detection surface of the front detector 61 and the rear detector 62 can be reduced. This is because by reducing the effective area of the detection surface, the decrease in the solid angle with the subject can be compensated by the above-described movement of the front detector 61 and the rear detector 62. In addition, by configuring the effective area on the detection surface of the front detector 61 and the rear detector 62 to be small, the front detector 61 and the rear detector 62 can be precisely moved and the cost can be reduced. Can be made.

  FIG. 11 is a block diagram showing another embodiment of the photon measuring apparatus according to the present invention. 11 also omits the information collection device 63, the image reconstruction device 64, and the display device 65 shown in FIG.

  In FIG. 11, a front detector 61 and a rear detector 62 are sequentially arranged in front of the subject 50. The front-stage detector 61 and the rear-stage detector 62 are spaced apart by a distance L.

  In this case, the position adjustment mechanism 66 of the front-stage detector 61 can adjust the movement of the front-stage detector 61 in the direction perpendicular to the detection surface, for example, and the position adjustment mechanism 67 of the rear-stage detector 62 can adjust the position of the rear-stage detector 62, for example. It is assumed that the movement can be adjusted in the direction perpendicular to the detection surface. Thereby, the front detector 61 can be disposed close to or in close contact with the subject 50, or the distance L between the front detector 61 and the rear detector 62 can be arbitrarily set.

  Further, the pre-stage detector 61 is configured to cover a part of the periphery of the subject 50 as a whole shape. For example, three detectors 61a, 61b, 61c having a flat plate shape are prepared, and the detector 61b is provided. It is arranged in the middle, and detectors 61a and 61c are fixed on both sides with an obtuse opening angle. The post-stage detector 62 is also configured to cover a part around the subject 50 as an overall shape. For example, three detectors 62a, 62b, and 62c having a flat plate shape are prepared, and the detector 62b is in the middle. The detectors 62a and 62c are fixed on both sides with an obtuse opening angle.

  In the front detector 61 and the rear detector 62, the plurality of detectors each having a flat plate shape are not formed by assembling separate detectors, but are integrally formed from the beginning of manufacture. May be.

  Even if the photon measuring apparatus configured in this way does not have a configuration in which the front-stage detector 61 and the rear-stage detector 62 can be moved around the subject 50, it is possible to perform imaging over most of the periphery of the subject 50. Thus, the geometric detection efficiency can be improved.

  FIG. 12 is a block diagram showing another embodiment of the photon measuring apparatus according to the present invention and corresponds to FIG.

  The configuration different from FIG. 11 is constituted by a plurality of flat detectors 62a, 62b, 62c in the rear detector 62, but only one flat detector in the front detector 61. It consists of

  Even in this case, since the post-stage detector 62 is configured to cover a part around the subject 50 as a whole shape, the imaging range can be expanded in imaging around the subject 50. Thus, the geometric detection efficiency can be improved.

  FIG. 13 is a block diagram showing another embodiment of the photon measuring apparatus according to the present invention and corresponds to FIG.

  11 differs from the case of FIG. 11 in that the front detector 61 is composed of a plurality of flat detectors 61a, 61b, 61c, but the rear detector 62 has one flat plate. This is because it is composed of only a detector.

  Even in this case, since the pre-stage detector 61 is configured to cover a part around the subject 50 as a whole shape, the imaging range can be enlarged in imaging around the subject 50. Thus, the geometric detection efficiency can be improved.

  FIG. 14 is a block diagram showing another embodiment of the photon measuring apparatus according to the present invention and corresponds to FIG.

  The configuration different from the case of FIG. 13 is that the post-stage detector 62 is configured as an annular body made of, for example, a ring covering the subject 50 and the pre-stage detector 61.

  When configured in this manner, the post-stage detector 62 can be configured without including the movement adjusting mechanism 67 provided in the above-described embodiment, for example.

  As an application example of this embodiment, for example, a pre-stage detector 61 (and a movement adjustment mechanism 66 if necessary) is arranged in a positron emission tomography (PET) apparatus having a conventionally known configuration, A detector element that has been previously provided in accordance with a positron emission tomography (PET) apparatus can be used as the post-stage detector 62 as it is.

  Thus, by constructing an existing positron emission tomography (PET) device as a so-called Compton camera, it is possible to use an existing SPECT preparation, and the effect of increasing the types of radiopharmaceuticals to be used Play. Since the existing apparatus is applied as it is, the development cost can be greatly reduced.

  In FIG. 14, the front detector 61 is configured to include a plurality of flat detectors 61 a, 61 b and 61 c in order to enlarge the covering around the subject 50. However, the present invention is not limited to this. For example, the detector 61b may be used alone.

  FIG. 15 is a block diagram showing another embodiment of the photon measuring apparatus according to the present invention and corresponds to FIG.

  A configuration different from the case of FIG. 13 is that the rear detector 62 is configured as a gamma camera that rotates around the subject 50 and moves. Here, the gamma camera is configured with the mechanical collimator removed.

  For this reason, the apparatus shown in this embodiment arranges the former detector 61 (and the movement adjustment mechanism 66 if necessary) in the former single photon emission CT (SPECT) apparatus from which the mechanical collimator is removed, A detector element that has been conventionally provided in accordance with a single photon emission CT (SPECT) apparatus can be used as the post-stage detector 62 as it is.

  In this way, by configuring the existing single photon emission CT (SPECT) device as a so-called Compton camera, it is possible to use existing PET preparations and increase the types of radiopharmaceuticals to be used. Play. Since the existing apparatus is applied as it is, the development cost can be greatly reduced.

  In FIG. 15, the front detector 61 is configured to include a plurality of flat detectors 61a, 61b, 61c in order to enlarge the covering around the subject 50. However, the present invention is not limited to this. For example, the detector 61b may be used alone.

  In the above-described embodiment, a photon measuring apparatus using a Compton camera using Compton scattering is shown. However, it may be a photon measuring device using an electron / positron pair generation reaction instead of Compton scattering (reaction). This is because the same effect can be obtained. In this case, the above scattered photons are replaced with electrons or positrons.

  In the above-described embodiment, a Compton camera applied to a nuclear medicine diagnostic apparatus is shown. However, the present invention is not limited to such a nuclear medicine diagnostic apparatus, and may be configured as, for example, a Compton camera used in a laboratory or the like, that is, a molecular imaging device.

  Each of the embodiments described above may be used alone or in combination. This is because the effects of the respective embodiments can be achieved independently or synergistically.

It is a block diagram which shows one Example of the Compton camera used for the nuclear medicine diagnostic apparatus by this invention, and is the figure which showed the aspect which has detected the comparatively low energy gamma ray. It is a block diagram which shows one Example of the Compton camera used for the nuclear medicine diagnostic apparatus by this invention, and is the figure which showed the aspect which has detected the comparatively high energy gamma ray. It is a top view which shows one Example of the detector with which the front | former detector of the said Compton camera is equipped. It is a schematic explanatory drawing which shows one Example of the nuclear medicine diagnostic apparatus using the said Compton camera. It is explanatory drawing which shows a part of operation | movement of the Compton camera used for the nuclear medicine diagnostic apparatus by this invention. It is a block diagram which shows the other Example of the Compton camera used for the nuclear medicine diagnostic apparatus by this invention. It is a block diagram which shows one Example of the photon measuring device applied to the nuclear medicine diagnostic apparatus by this invention. It is explanatory drawing for demonstrating the effect of enlarging the distance L between a front | former stage detector and a back | latter stage detector in the photon measuring device applied to the nuclear medicine diagnostic apparatus by this invention. It is explanatory drawing which shows each aspect of operation | movement of the front | former stage detector and back | latter stage detector of the photon measuring device applied to the nuclear medicine diagnostic apparatus by this invention. It is a block diagram which shows the other Example of the photon measuring device applied to the nuclear medicine diagnostic apparatus by this invention. It is a block diagram which shows the other Example of the photon measuring device applied to the nuclear medicine diagnostic apparatus by this invention. It is a block diagram which shows the other Example of the photon measuring device applied to the nuclear medicine diagnostic apparatus by this invention. It is a block diagram which shows the other Example of the photon measuring device applied to the nuclear medicine diagnostic apparatus by this invention. It is a block diagram which shows the other Example of the photon measuring device applied to the nuclear medicine diagnostic apparatus by this invention. It is a block diagram which shows the other Example of the photon measuring device applied to the nuclear medicine diagnostic apparatus by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Compton camera, 2 ... Incident gamma ray, 3 ... Scattering gamma ray, 4 ... Recoil electron, 5 ... Trajectory (of recoil electron), 10 ... First front detector, 10A ... Gas package DESCRIPTION OF SYMBOLS 10B ... Detector, 20 ... 2nd front stage detector, 20A ... Gas package, 20B ... Detector, 30 ... Back stage detector, 11 ... Semiconductor substrate, 12 ... Cathode, 13 ... Transparent Hole 14... Anode 20. Wiring layer 41. Information collecting device 42 image reconstructing device 43 display device 50 subject 51 51 photon 52 scattered photon 60... Photon measuring device 61... Pre-stage detector 62... Post-stage detector 63 63 Information collecting device 64. , 21O …… Moving trajectory of the former detector, 22O …… Moving trajectory of the latter detector A ...... Compton scattering point, the absorption point of B ...... scattered photons, e ...... recoil electrons.

Claims (8)

Compton camera equipped with a pre-stage detector for detecting information of charged particles that are filled with gas and generated by Compton scattering in the gas, and a post-stage detector for detecting information of scattered photons,
A nuclear medicine diagnostic apparatus characterized in that a plurality of the former detectors having different types of gas are stacked. Compton camera equipped with a front stage detector that detects information of charged particles that are filled with gas and generated by Compton scattering in the gas, and a rear stage detector that detects information of scattered photons,
2. A nuclear medicine diagnostic apparatus comprising a plurality of the front-stage detectors having different types of gas arranged side by side in a plane. A pre-stage detector for reacting photons emitted from a subject to detect position information at a first reaction point and information on momentum of charged particles generated by the reaction; and the charged particle mechanically separated from the pre-stage detector Or a post detector that detects information about photons scattered by the reaction;
Image reconstruction means for imaging the photon source in the subject from each information from the front detector and the rear detector;
An apparatus for measuring a photon, comprising an adjusting means capable of changing a distance between the front detector and the rear detector.   4. The photon measuring apparatus according to claim 3, further comprising a mechanism that brings the front detector close to or in close contact with a subject.   The photon measurement apparatus according to claim 3, further comprising a mechanism for rotating the front-stage detector around the subject in a state where the front-stage detector is oriented forward with the rear-stage detector.   4. The photon measuring device according to claim 3, further comprising a mechanism for rotating the latter detector around the subject in a state where the latter detector is oriented forward with the former detector.   6. The photon measuring apparatus according to claim 5, wherein the post-stage detector is formed of an annular body surrounding the subject.   6. The photon measuring apparatus according to claim 5, wherein the front-stage detector is composed of an annular body surrounding the subject.

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