JP2015222193A - Radiation measuring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation measuring system capable of easily performing measurement.SOLUTION: The measurement is made by calculating amount of radiation which is emitted from the inside of an analyte on the basis of detection signals of radiation output from a detector group 12. By eliminating imaging using radiopharmaceutical, the medicine quantity to be administered to the analyte can be reduced. When the signal strength is reduced by reducing the medicine quantity, noise components considerably appear. To solve the problem, the radiation measuring system includes a shield 13 for shielding, from the radiation, the faces other than faces facing to the analyte in the faces included in the radiation detector constituting the detector group 12. With this arrangement, the noise components can be reduced more than conventional.

Description

  The present invention relates to a radiation measurement apparatus that detects radiation emitted from within a subject.

  A medical institution is equipped with a radiation tomography apparatus that images the distribution of a radiopharmaceutical. Such a radiation tomography apparatus includes a detector group in which radiation detectors for detecting radiation are arranged in an annular shape. This detector group detects a pair of radiations flying away in opposite directions that are generated when positrons generated from the radiopharmaceutical in the subject disappear. Such an apparatus indirectly detects a radiopharmaceutical when a pair of radiation is generated from positrons on a straight line connecting the incident positions when two radiations are simultaneously incident on the detector group. More specifically, the spatial distribution of the radiopharmaceutical is obtained by counting events in which two radiations are simultaneously incident on the detector group. Such an apparatus is called a PET (Positron Emission Tomography) apparatus, and the counting of events performed by the PET apparatus is called coincidence counting (for example, see Non-Patent Document 1 and Non-Patent Document 2).

  In addition, medical institutions include devices that image radiopharmaceuticals on a principle different from that of PET devices. Such a radiation tomography apparatus is also provided with a detector group in which radiation detectors for detecting radiation are arranged in an annular shape. The detector group indirectly detects the radiopharmaceutical by detecting single-photon type radiation generated from the radiopharmaceutical in the subject. A collimator is provided between the detector group and the subject, and only the radiation that has passed through the collimator is incident on the detector group. Unlike a pair of radiation derived from positrons, the single-photon type radiation detected at a certain part of the detector group does not know from which direction it flew toward this part. Therefore, in such an apparatus, by providing the collimator, the direction in which the radiation generated in the subject can enter the detector group is limited. This makes it possible to know from which direction the radiation detected at a certain part of the detector group has been blown. Such an apparatus is called a SPECT (Single Photon Emission Computed Tomography) apparatus (for example, see Non-Patent Document 3).

Such a device has been applied to various diagnoses such as a diagnosis for specifying the position of cancer tissue in the body.
Shimadzu review 61, 99-104 (2004) Development of positron ECT device Eminence-G for whole body Shimadzu review 51, 59-65 (1994) Development of positron ECT equipment HEADTOME-V (SET-2000W series) Shimadzu review 57,247-254 (2001) Development of SPECT device SET-080Alpha for head

However, the conventional apparatus has the following problems.
That is, in all scenes, the conventional apparatus is not necessarily an appropriate configuration.

  It has been pointed out that amyloid β may be useful as a marker for predicting dementia. This amyloid β begins to accumulate in the brain before the symptoms of dementia actually appear. Therefore, if the accumulation state of amyloid β in the brain is known, dementia may be predicted.

  To know the accumulation of amyloid β in the brain, a radiation measuring device is used. When PIB (Pittsburgh Compound-B), which is thought to bind to amyloid β, is radioactively labeled and administered to a subject, PIB collects in a portion where amyloid β in the brain is localized at a high concentration . Since this PIB emits radiation, if this radiation is detected, the concentration of amyloid β in the brain should be known.

  However, there are circumstances in which it is difficult to use a conventional PET apparatus or SPECT apparatus for measurement of amyloid β accumulation. These devices are configured for the purpose of imaging the distribution of the radiopharmaceutical. If a tomographic image of a subject is to be generated, so much radiation must be detected. A tomographic image for imaging purposes is required to have a higher S / N ratio. Therefore, the radioactivity of the radiopharmaceutical administered to the subject by injection is relatively strong. In addition, the time required for measurement is long because of the need to detect as much radiation as possible. In order to perform imaging with the configuration of the conventional apparatus, it is required to maintain a posture in which the subject is surrounded by the detector group for about 10 minutes to several tens of minutes.

  That being said, it is impossible to say whether it is necessary to know the accumulation of amyloid β. What is obtained from the accumulation state of amyloid β is only a prediction that it may become dementia in the future. There is a possibility that amyloid β does not become dementia even if it accumulates in the brain. Therefore, the question arises as to whether it is necessary to image amyloid β until exposure risk and the inconvenience of being restrained for a long time.

  However, the disease of dementia is still a mystery and it is necessary to gather as much knowledge as possible. Therefore, development of a device that can more easily know the accumulation of amyloid β in the brain is desired.

  This invention is made | formed in view of such a situation, The objective is to provide the radiation measuring device which can be measured easily.

The present invention has the following configuration in order to solve the above-described problems.
That is, the radiation measurement apparatus according to the present invention includes a detector group including a plurality of radiation detectors arranged so as to surround a part of the subject at the same position in the body axis direction of the subject, and a detection Based on the radiation detection signal output from the detector group, the calculation means for calculating the radiation dose emitted from the subject, and the surface of the radiation detector constituting the detector group facing the subject. And a shielding body that shields a surface other than the existing surface from radiation.

  [Operation / Effect] The radiation measuring apparatus of the present invention is optimized in specific radiation measurement. That is, in the present invention, the measurement is completed by calculating the radiation dose emitted from the inside of the subject based on the radiation detection signal output from the detector group. By omitting radiopharmaceutical imaging in this way, the amount of drug administered to the subject can be suppressed. When the amount of the drug is reduced to suppress the signal intensity, the noise component becomes conspicuous. In order to solve this problem, the configuration of the present invention includes a shielding body that shields, from radiation, surfaces other than the surface facing the subject among the surfaces of the radiation detectors constituting the detector group. . If comprised in this way, a noise component can be suppressed now more than the conventional structure.

  In the radiation measurement apparatus described above, it is more desirable that a part of the subject surrounded by the radiation detectors constituting the detector group is the head.

  [Operation / Effect] The above-described configuration makes the device of the present invention more specific. If a part of the subject surrounded by the radiation detectors constituting the detector group is the head, the apparatus is suitable for detecting accumulation of amyloid β.

  In the radiation measurement apparatus described above, the shield covers the detector group from one side in the body axis direction of the subject, and the detector group covers the detector group from the other side in the body axis direction of the subject. It is more desirable that the other side covering material and the side surface covering material that covers the radiation detector exposed at the position sandwiched between the one side covering material and the other side covering material.

  [Operation / Effect] The above-described configuration makes the device of the present invention more specific. If the shield is composed of three covering materials, the detector group is more reliably shielded from extraneous radiation.

  Further, in the above-described radiation measuring apparatus, the one-side covering material is not provided with a through-hole for introducing the subject into the detector group from the body axis direction, and the other-side covering material is provided with the subject. It is more desirable if a through hole is provided to be introduced into the detector group from the body axis direction.

  [Operation / Effect] The above-described configuration makes the device of the present invention more specific. As described above, if the shield is configured so as not to provide the entrance / exit for introducing the subject as much as possible, the detector group can be more reliably shielded from extraneous radiation.

  In the above-described radiation measuring apparatus, it is more preferable that the one-side coating material and the other-side coating material are each provided with a through hole for introducing the subject into the detector group from the body axis direction.

  [Operation / Effect] The above-described configuration makes the device of the present invention more specific. As described above, if the entrances for introducing the subject are provided on both sides of the shield, a radiation measuring apparatus that is more convenient to use can be provided.

  In the above-described radiation measuring apparatus, it is more desirable if a collimator is provided between the subject and the detector group.

  [Operation / Effect] The above-described configuration makes the device of the present invention more specific. If a collimator is provided between the subject and the detector group, the detector group can be more reliably shielded from extraneous radiation.

  In the above-described radiation measurement apparatus, it is more desirable that correction means for correcting data indicating the radiation dose calculated by the calculation means with different parameters between subjects is provided.

  [Operation / Effect] The above-described configuration makes the device of the present invention more specific. If the configuration is such that the data indicating the radiation dose is corrected as described above, the data can be compared with high reliability.

  The radiation measuring apparatus of the present invention is optimized in specific radiation measurement. That is, in the present invention, the measurement is completed by calculating the radiation dose emitted from the inside of the subject based on the radiation detection signal output from the detector group. By omitting radiopharmaceutical imaging in this way, the amount of drug administered to the subject can be suppressed. When the amount of the drug is reduced to suppress the signal intensity, the noise component becomes conspicuous. In order to solve this problem, the configuration of the present invention includes a shielding body that shields, from radiation, surfaces other than the surface facing the subject among the surfaces of the radiation detectors constituting the detector group. . If comprised in this way, a noise component can be suppressed now more than the conventional structure.

1 is a functional block diagram illustrating an overall configuration of a radiation measuring apparatus according to Embodiment 1. FIG. FIG. 3 is a plan view illustrating a configuration of a detector group according to Embodiment 1. 1 is a perspective view illustrating a configuration of a radiation detector according to Embodiment 1. FIG. It is sectional drawing explaining the meaning of the shield which concerns on Example 1. FIG. It is a disassembled perspective view explaining the structure of the shielding body which concerns on Example 1. FIG. FIG. 3 is a schematic diagram illustrating a configuration of a data correction unit according to the first embodiment. 3 is a flowchart for explaining the operation of the radiation measuring apparatus according to the first embodiment. It is a disassembled perspective view explaining 1 modification of this invention. It is a disassembled perspective view explaining 1 modification of this invention. It is sectional drawing explaining 1 modification of this invention. It is sectional drawing explaining 1 modification of this invention.

  Embodiments of a radiation measuring apparatus according to the present invention will be described below with reference to the drawings. The gamma rays in Example 1 are an example of the radiation of the present invention. Note that the apparatus according to the first embodiment has a configuration specialized for estimating the accumulation amount of amyloid β in the brain of the subject M, unlike the conventional PET apparatus and SPECT apparatus focusing on imaging. .

<Overall configuration of radiation measuring apparatus 9>
FIG. 1 is a functional block diagram illustrating a specific configuration of the radiation measuring apparatus 9 according to the first embodiment. The radiation measuring apparatus 9 according to the first embodiment includes a ring-shaped detector group 12 that surrounds the head of the subject M, and a shield 13 that shields the detector group 12 from external radiation such as radiation derived from cosmic rays. It has. The opening for introducing the head provided in the detector group 12 has a cylindrical shape (exactly a polygonal column) extending in the z direction (the body axis direction of the subject M). Therefore, the center axis of the detector group 12 in the ring shape extends in the z direction. In addition, the area | region of the opening part of the detector group 12 is an area | region which the radiation measuring device 9 can detect a gamma ray.

  The top plate 10 is provided for the purpose of placing the subject M. The top board 10 can move in the z direction in accordance with a movement instruction made by the operator through the console 31. By moving the top 10, the head of the subject M can be introduced into the detector group 12, or the head already introduced into the detector group 12 can be taken out from the detector group 12. it can. The top plate 10 is supported by a support base 10a that supports the top plate 10 movably in the z direction.

  The configuration of the detector group 12 will be described. The detector group 12 is composed of a ring in which a plurality of radiation detectors 1 are arranged in a virtual circle on a plane perpendicular to the z direction (center axis direction) (specifically, refer to FIG. 2). The detector group 12 includes a plurality of radiation detectors arranged so as to surround a part of the subject M at the same position in the body axis direction of the subject M. The part of the subject M surrounded by the radiation detectors constituting the detector group 12 is specifically the head. Further, the detector group 12 may be configured by stacking a plurality of rings shown in FIG. 2 in the z direction.

  The configuration of the radiation detector 1 will be briefly described. FIG. 3 is a perspective view illustrating the configuration of the radiation detector according to the first embodiment. As shown in FIG. 3, the radiation detector 1 includes a scintillator 2 that converts radiation into light, and a photodetector 3 that includes a photomultiplier tube that detects light. A light guide 4 for transmitting and receiving light is provided at a position where the scintillator 2 and the photodetector 3 are interposed.

The scintillator 2 is configured by scintillator crystals arranged three-dimensionally. The scintillator crystal is composed of Gd ₂ SiO ₅ (hereinafter referred to as GSO) in which Ce is diffused. As a material for the scintillator crystal, it is desirable to select a material that does not contain Lu with self-radiation for the purpose of preventing background counting. The light detector 3 can specify the light generation position of which scintillator crystal emits light, and also specifies the light intensity and the time when the light is generated. Can do. The scintillator 2 having the configuration of the first embodiment is merely an example of an aspect that can be adopted. Therefore, the configuration of the present invention is not limited to this. The light guide 4 is located between the scintillator 2 and the light detector 3, and is configured to transmit the fluorescence generated by the scintillator 2 to the light detector 3.

  Further, the radiation detector described in FIG. 3 is used for a conventional PET apparatus. The radiation detector of the apparatus according to the present invention only needs to be able to distinguish the presence or absence of incidence of γ rays, and does not need to specify the position where the scintillator 2 generates fluorescence. Therefore, the configuration of the radiation detector arranged in the apparatus according to the present invention may be simpler than that described in FIG. For example, it is possible to configure a radiation detector using the scintillator 2 in which each of the scintillator crystals is enlarged and the number of crystals is reduced, or the photodetector 3 having no function of specifying the fluorescence generation position. However, in order to aim for a device that is resistant to noise, it is better to employ a radiation detector having energy resolution and time resolution.

<About the structure of the shield 13>
Next, the configuration of the shield 13 will be described. The shield 13 is a member that shields five surfaces other than the incident surface on which γ-rays that are farthest from the light guide 4 are incident among the six surfaces of the radiation detector 1 having a rectangular parallelepiped shape. is there. This incident surface is also a surface arranged in a direction facing the subject M when the radiation detectors 1 are arranged to constitute the detector group 12. The shield 13 shields the surfaces other than the surface facing the subject M among the surfaces of the radiation detector 1 constituting the detector group 12 from the radiation.

  The shield 13 is made of, for example, lead that does not easily transmit radiation. The five surfaces of the radiation detector 1 are covered with the shield 13 with a material having a radiation absorption property of about 5 cm in thickness.

  The shield 13 is generated outside the head of the subject M, and absorbs γ-rays derived from a radiopharmaceutical to be incident on the radiation detector 1. Radiopharmaceuticals travel throughout the body of the subject during the examination. Therefore, radiation derived from the radiopharmaceutical is generated from other than inside the detector group 12. Among such radiations, there are those that hinder the inspection to fly in an oblique direction and enter the radiation detector 1 as shown in FIG. According to the present invention, γ-rays generated outside the head are absorbed by the shield 13 and do not enter the radiation detector 1 and do not cause a decrease in the S / N ratio.

  The shield 13 also absorbs a part of γ rays derived from cosmic rays that hinder the inspection. Therefore, the shield 13 reduces the probability that γ rays derived from cosmic rays enter the radiation detector 1 and contributes to the prevention of a decrease in the S / N ratio.

  The conventional PET apparatus also has a shield that prevents the γ rays derived from the portion protruding from the detector group 12 of the subject M from entering the detector group 12. However, this shield is only attached to both end faces of the detector group 12 in the body axis direction, and its thickness is not as thick as the present invention. Even in the PET apparatus, the problem is that the S / N ratio is lowered due to the γ-rays generated outside the head flying in an oblique direction, but this is not a serious problem. The PET apparatus is configured to count annihilation radiation pairs. In the PET apparatus, even if γ rays generated outside the head are detected by chance, the radiation that forms the pair is not detected, and therefore the data is discarded. The same situation applies to radiation derived from cosmic rays. As described above, the PET apparatus is configured to be resistant to noise.

  Since the SPECT apparatus also has a collimator between the subject M and the radiation detector, γ rays generated outside the head are rarely incident on the radiation detector. Certainly, even in the conventional SPECT apparatus, there is a shield that prevents the γ rays derived from the portion of the subject M protruding from the detector group 12 from entering the detector group 12. However, this shield is only attached to both end faces of the detector group 12 in the body axis direction, and its thickness is not as thick as the present invention.

  In contrast, the configuration of the present invention only detects the presence or absence of radiation, so whether the detected radiation is gamma rays derived from the head or other than the head or cosmic rays. There is no way to distinguish whether the radiation comes from. Therefore, the present invention is configured based on the idea of prohibiting radiation from being incident on the radiation detector from the beginning. In the configuration of the present invention, the S / N is improved by providing the shield 13. Thereby, even if the dose of the radiopharmaceutical is very small, highly reliable detection can be performed. Such a situation can be said to be desirable from the viewpoint of reducing radiation exposure to the subject M.

  By the way, according to the apparatus of the present invention, the inspection can be completed in a much shorter time using a much smaller radiation dose than the inspection using the PET apparatus or the SPECT apparatus. The PET apparatus can use only about 1/100 of the detected gamma rays for imaging. This is because the PET apparatus has a constraint that γ rays are not detected unless a γ ray pair is detected. Similarly, the SPECT apparatus can use only about 1/1000 of the detected γ rays for imaging. In the SPECT apparatus, there is a constraint that γ rays are not detected unless the γ rays have a predetermined energy. In the SPECT apparatus, the detection result regarding the γ-ray that has weakened while passing through the collimator before entering the radiation detector is discarded. Accordingly, the detection of γ rays has become useless.

  According to the configuration of the present invention, detection that is not converted into data can be reduced. By deciding not to acquire information on the generation position of γ-rays, the number of γ-rays that can be used for calculation of the results has greatly increased. According to the configuration of the present invention, most of the detected γ-rays can be used for calculating the radiopharmaceutical concentration. For example, detection of γ-rays emitted from the subject M can be completed within one minute. it can.

  FIG. 5 illustrates how the shield 13 shields the detector group 12. As shown in FIG. 5, the shield 13 includes a one-side covering material 13 a that covers the detector group 12 from one side in the z direction, and another side covering material 13 b that covers the detector group 12 from the other side in the z direction. And a side surface covering material 13c that covers the radiation detector 1 exposed at a position sandwiched between the one side covering material 13a and the other side covering material 13b. That is, the shield 13 is such that the one-side covering material 13a having a disk shape, the ring-shaped side surface covering material 13c, and the other-side covering material 13b having a ring shape are arranged side by side in the z direction. It has a configuration. The detector group 12 is accommodated in a cylindrical hollow generated by the one side covering material 13a, the other side covering material 13b, and the side surface covering material 13c.

  The opening opened in the other side covering material 13 b is an entrance when the head of the subject M is taken in and out of the detector group 12. This opening is smaller than the inner diameter of the detector group 12 as shown in FIG. Therefore, the other side covering material 13 b when viewed from the inside of the detector group 12 is configured to protrude from the detector group 12. By setting it as such a structure, the shielding capability of the shielding body 13 can be improved. That is, the one-side covering material 13a is not provided with a through hole for introducing the subject M into the detector group 12 from the body axis direction, and the other-side covering material 13b is provided with the subject M on the body axis. A through hole is provided to be introduced into the detector group 12 from the direction.

  The radiation detector 1 constituting the detector group 12 has five surfaces other than the incident surface. Three of them are a surface with which the one-side covering material 13a abuts, a surface with which the other-side covering material 13b abuts, and a surface with which the side surface covering material 13c abuts. These three surfaces are shielded by the covering material with which they abut. Of the five surfaces of the radiation detector 1, the remaining two are the surfaces facing the adjacent radiation detectors. These surfaces are shielded by the shield 13. Belongs to the ring-shaped shadow area. Therefore, among the six surfaces of the radiation detector 1, only the incident surface facing the head of the subject M set in the apparatus is not shielded by the shield 13.

  The dose calculation unit 20 calculates the γ-ray dose detected based on the γ-ray detection signal output from the detector group 12. The dose calculation unit 20 does not necessarily perform simultaneous counting performed by a PET apparatus or the like. Dose data, which is a calculation result of the dose calculation unit 20, represents the amount of γ rays incident on the detector group 12. The dose calculation unit 20 corresponds to the calculation means of the present invention.

<About the data correction unit 21>
The data correction unit 21 is configured to correct the data indicating the radiation dose calculated from the dose calculation unit 20 with different parameters between the subjects M. The dose data output from the dose calculation unit 20 may not be reliable by itself. The reason for this will be described. Even if it is attempted to compare dose data obtained among a plurality of subjects M, the amount of administered radiopharmaceutical is not always the same among the subjects M. Therefore, according to the present invention, the data correction unit 21 is provided for the purpose of correcting the difference in the dose of the radiopharmaceutical. The data correction unit 21 acquires a value regarding the dose of the radiopharmaceutical input by the operator through the console 31 and divides the dose data output by the dose calculation unit 20 by this value. Thus, the dose data is normalized in terms of radiopharmaceutical dosage. The data correction unit 21 corresponds to correction means of the present invention.

  The data correction unit 21 is configured to perform corrections other than the above correction. The physique of the subject M varies depending on the subject M. Accordingly, even if the same amount of radiopharmaceutical is administered to the subject M, the concentration in the subject varies.

  Therefore, according to the apparatus of the present invention, a function of correcting data is provided so that detection results can be compared among a plurality of subjects M. That is, the storage unit 32 according to the present invention stores a table in which the weight and the count of the subject M are associated as shown in FIG. When the data correction unit 21 receives the dose data output from the dose calculation unit 20, the data correction unit 21 acquires the weight of the subject M input by the operator through the console 31, and the corresponding coefficient is obtained from the above table. Recognize Then, the data correction unit 21 completes the correction of the data by multiplying the dose data by the above-described coefficient.

  As a method of creating a table stored in the storage unit 32, a method of determining a coefficient so as to be proportional to the weight can be considered. That is, the coefficient is set so that the weight is doubled when the weight is doubled. When the weight of the subject M is doubled, it can be roughly considered that the volume of the subject M is doubled. Therefore, when the volume of the subject M is doubled, the concentration of the radiopharmaceutical to be administered should be halved throughout the body. Based on this, when trying to compare the subject M and the subject M whose body weight is twice that of the subject M, a correction is made so that only the dose data obtained from the subject M whose body weight is twice is doubled. It turns out that it is necessary to apply. The coefficient can be created based on such a principle.

  In the configuration of FIG. 6, the table relates to the weight and the coefficient, but instead of this, a table related to the height and the coefficient may be used. Further, a table in which the head circumference and the coefficient are related may be used. The subject M needs to input information on the subject M corresponding to the type of table from the console 31. The relationship between the parameters unique to the subject and the coefficients may be stored by an equation.

  The radiation measuring apparatus 9 includes a main control unit 41 that controls each unit in an integrated manner. The main control unit 41 is constituted by a CPU, and realizes the units 20 and 21 by executing various programs. In addition, each above-mentioned part may be divided | segmented into the control apparatus which takes charge of them. The display unit 30 is provided for the purpose of displaying the measurement result. The storage unit 32 stores all data necessary for the operation of the apparatus.

<Operation of Radiation Measuring Device 9>
Next, the operation of the radiation measuring apparatus 9 according to the present invention will be described with reference to FIG. In order to perform γ-ray measurement using the apparatus of the present invention, first, a radiopharmaceutical is injected into a subject (drug administration step S1). The drug administered at this time may be a positron emitting radiopharmaceutical or a single photon emitting radiopharmaceutical. Then, the subject M is placed on the top board 10, and the head of the subject M is guided into the detector group 12 (subject placement step S2). When the surgeon instructs the start of detection of γ rays through the console 31, the apparatus starts detecting γ rays. This detection of γ rays is completed in about 1 minute, for example (detection step S3). The dose data that is the detection result is subjected to various corrections by the data correction unit 21 (correction step S4). The corrected dose data is displayed on the display unit 30, and the operation of the apparatus according to the present invention is terminated.

  As described above, the radiation measuring apparatus 9 of the present invention is optimized for specific radiation measurement. In other words, in the present invention, the measurement is completed by calculating the radiation dose emitted from within the subject based on the radiation detection signal output from the detector group 12. By omitting radiopharmaceutical imaging in this way, the amount of drug administered to the subject can be suppressed. When the amount of the drug is reduced to suppress the signal intensity, the noise component becomes conspicuous. In order to solve this problem, the configuration of the present invention shields the radiation detector 1 constituting the detector group 12 from the radiation other than the surface facing the subject M among the surfaces of the radiation detector 1. It has. If comprised in this way, a noise component can be suppressed now more than the conventional structure.

  The present invention is not limited to the above-described embodiments, and can be modified as follows.

  (1) The above-described detector group 12 is configured by arranging the radiation detectors 1 in an annular shape, but the present invention is not limited to this configuration. The number of radiation detectors 1 can be further reduced. For example, the configuration of the present invention can employ the detector group 12 having a configuration in which the radiation detectors are arranged on the top, bottom, left and right of the head of the subject M.

  (2) Although the above-described shield 13 has a cylindrical shape, the present invention is not limited to this configuration. As shown in FIG. 8, you may make it comprise the shielding body 13 with the rectangular one side coating | covering material 13a, the other side coating | covering material 13b, and the side surface covering material 13c of a square cylinder shape. 8 is suitable for the detector group 12 having a configuration in which the radiation detectors described above are arranged on the top, bottom, left, and right of the head of the subject M. Depending on the number of radiation detectors constituting the detector group 12, the shields 13 can be triangular or other polygonal shapes.

  (3) Although the above-described shield 13 is configured to shield the detector group 12 integrally, the present invention is not limited to this configuration. As shown in FIG. 9, it is good also as a structure provided with the some shield which covers the radiation detector 1 which comprises the detector group 12 separately.

  (4) Although the entrance / exit of the subject M is not provided in the one-side covering material 13a of the shield 13 described above, the present invention is not limited to this configuration. As shown in FIG. 10, the one-side covering material 13a can be provided with an opening similar to that of the other-side covering material 13b. According to such a modification, the one-side covering material 13a and the other-side covering material 13b are provided with through holes for introducing the subject M into the detector group 12 from the z direction. Become.

  (5) In addition to the above-described configuration, a collimator 14 may be provided between the head of the subject M and the radiation detector 1 as shown in FIG. The collimator 14 is configured by arranging a scepter plate that allows passage of radiation from the head of the subject M toward the radiation detector 1 and absorbs radiation intended to cross the collimator 14 from other directions. Due to the presence of the collimator 14, the radiation measuring device 9 that has passed through the opening provided in the other side covering material 13b and is about to enter the radiation detector 1 is cut, and the S / N ratio is further improved. Can be provided. In the apparatus of the present invention, since the strong shield 13 is provided, the radiation dose blocked by the collimator 14 is not so large in the first place. Accordingly, the coarser collimator 14 can be employed as compared with the conventional SPECT apparatus.

DESCRIPTION OF SYMBOLS 1 Radiation detector 12 Detector group 13 Shielding body 13a One side coating material 13b The other side coating material 13c Side surface coating material 20 Dose calculation part (calculation means)
21 Data correction unit (correction means)

Claims (7)

A detector group comprising a plurality of radiation detectors arranged so as to surround a part of the subject at the same position in the body axis direction of the subject;
Based on the radiation detection signal output from the detector group, calculating means for calculating the radiation dose emitted from within the subject;
A radiation measuring apparatus comprising: a shielding body that shields a surface of the radiation detector included in the detector group other than the surface facing the subject from the radiation. The radiation measurement apparatus according to claim 1,
The radiation measuring apparatus according to claim 1, wherein a part of the subject surrounded by the radiation detectors constituting the detector group is a head. The radiation measurement apparatus according to claim 1 or 2,
The shield includes a one-side covering material that covers the detector group from one side in the body axis direction of the subject, and another side covering material that covers the detector group from the other side in the body axis direction of the subject. A radiation measuring apparatus comprising: a side surface covering material that covers the radiation detector exposed at a position sandwiched between the one side covering material and the other side covering material. The radiation measurement apparatus according to claim 3.
The one-side covering material is not provided with a through-hole for introducing the subject from the body axis direction into the detector group,
The radiation measuring apparatus according to claim 1, wherein the other side covering material is provided with a through-hole through which the subject is introduced into the detector group from the body axis direction. The radiation measurement apparatus according to claim 3.
The one-side covering material and the other-side covering material are each provided with a through-hole through which a subject is introduced from the body axis direction into the detector group. The radiation measurement apparatus according to any one of claims 1 to 5,
A radiation measuring apparatus, wherein a collimator is provided between a subject and the detector group. The radiation measurement apparatus according to any one of claims 1 to 6,
A radiation measuring apparatus, comprising: correction means for correcting data indicating the radiation dose calculated by the calculating means with parameters different between subjects.

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