JP5169898B2 - Radiation tomography equipment - Google Patents

Description

  The present invention relates to a radiographic apparatus that images radiation emitted from a subject, and more particularly to a radiographic apparatus having a wide field of view to the extent that a body portion of a subject can be imaged at once.

  In the medical field, radiation tomography that detects tomographic images of radiopharmaceutical distribution in a region of interest of the subject by detecting annihilation radiation (for example, γ-rays) released from the radiopharmaceutical administered to the subject and localized in the region of interest Used in equipment (ECT: Emission Computed Tomography). ECT mainly includes a PET (Positoron Emission Tomography) apparatus, a SPECT (Single Photon Emission Computed Tomography) apparatus, and the like.

  A description will be given using a PET apparatus as an example. The PET apparatus has a detector ring in which block-shaped radiation detectors are arranged in a ring shape. This detector ring is provided to surround the subject and is configured to detect the radiation that has passed through the subject.

  First, the configuration of a conventional PET apparatus will be described. As shown in FIG. 11, a conventional PET apparatus 50 includes a gantry 51 having an introduction hole for introducing a subject, and a block-shaped radiation detection for detecting radiation so as to surround the introduction hole inside the gantry 51. And a support member 54 provided so as to surround the detector ring 53. For each of the radiation detectors 52, a bleeder unit 55 having a bleeder circuit is provided at a position where the support member 54 is interposed, and this connects the support member 54 and the radiation detector 52. Such a PET apparatus is described in Patent Document 1, for example.

  The PET device measures annihilation radiation pairs emitted from the radiopharmaceutical. That is, the annihilation radiation pair radiated from the inside of the subject M is a radiation pair whose traveling direction is opposite by 180 °. As shown in FIG. 12, in the detector ring 53, a detection element C for detecting an annihilation radiation pair is stacked in the z direction. Thereby, the position of the annihilation radiation pair with respect to the detector ring 53 can be discriminated in the z direction.

  A method for generating an image of such a PET apparatus will be described. General data processing is detailed in Patent Document 1, but here, a configuration in which Patent Document 1 is appropriately changed is shown. As shown in FIG. 13, the detection data output from the detector ring 53 is stored in the detection data storage unit 61. In order to generate a radiation tomographic image of a subject, it is necessary to continue detection of annihilation radiation pairs until the number of detection data reaches a predetermined amount. When the detection data score reaches a predetermined amount, the tomographic image generation unit 62 reads out the detection data stored in the detection data storage unit 61 and generates a tomographic image of the subject indicating the radiopharmaceutical distribution in the subject. The subject tomographic image is displayed on the display unit 63.

JP-A-8-24253

However, the conventional configuration described above has the following problems.
That is, it is difficult to observe the movement of the drug in the radiation tomography apparatus having the conventional configuration. In recent years, not only the distribution of drugs in a subject but also the scene that requires observation of changes in the localization of drugs over time is increasing. In order to observe such movement of the drug in the subject, it is necessary to acquire a plurality of tomographic images that are continuous over time at short time intervals. In the conventional configuration, it is difficult to capture such a tomographic image.

  The tomographic image generation unit 62 acquires a tomographic image when the number of detection data stored in the detection data reaches a predetermined amount. In FIG. 13, it is assumed that when a predetermined time has elapsed from the time point T0 when the inspection is started and the time point T1 is reached, the score of the detection data becomes a predetermined amount. The tomographic image generation unit 62 generates a tomographic image P1 based on the detection data group D1 accumulated during this time. Thereafter, the detection data storage unit 61 starts accumulation of the detection data again from the time point T1, and when the time point T2 is reached, it is assumed that the detection data score has reached a predetermined amount. A tomographic image P2 is generated based on the detection data group D2 accumulated during this time. Similarly, a tomographic image P3 is generated based on the detection data group D3 obtained between time T2 and time T3.

  That is, the time in the tomographic images P1 to P3 that are continuous over time cannot be made shorter than the time (for example, the time between the time point T0 and the time point T1) when the score of the detection data becomes a predetermined amount. Then, even if it is going to observe the change of the localization of a chemical | medical agent with time, rapid movement of a chemical | medical agent will not be observed. Therefore, according to the conventional configuration, if it is desired to observe the rapid movement of the drug, there is no choice but to increase the amount of the radio drug injected into the subject.

  Some drugs have different behavior in the subject depending on the dose. Therefore, the amount of radiopharmaceutical may not be increased or decreased freely. Therefore, even if the dose of the drug is increased, not all tests can be performed. Moreover, the radiation exposure dose of the subject increases by increasing the dose of the radiopharmaceutical.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a radiation tomography apparatus suitable for observing a change in localization of a drug over time.

In order to achieve the above object, the present invention has the following configuration.
That is, the radiation tomography apparatus according to claim 1 is configured such that the radiation detectors that detect the radiation are arranged in a ring shape, the detector ring that outputs the detection data, the detection data, and the point in time when the radiation is Detection data storage means for storing time information indicating whether or not the detection data is detected, tomographic image generation means for reading out a part of the detection data group stored in the detection data storage section and generating a radiation tomographic image, and tomographic image generation Radiation using a determination means for determining which detection data is read out from the detection data storage unit of the detection data group to the means, and detection data indicating the radiation detected by the detector ring during a certain period When creating a tomographic image, a start time storage means for storing a start time indicating the beginning of the period, and a target time for storing a target time indicating the length of the period Memory means and sampling interval storage means for storing a sampling interval indicating an interval between respective start times in the radiation tomographic images adjacent in time series, and the determination means refers to (A) time information and detects data Of the detection data stored in the storage means, the detection data detected by the detector ring within the target time starting from the start time point is recognized as a target data group used when generating a radiation tomographic image, (B) The target data group is sent to the tomographic image generation means, and the operations (A), (B), and (C) are repeated in which (C) the time after the sampling interval is reset as the next start time. Thus, the tomographic image generating means generates a series of radiation tomographic images in which continuous images are captured at intervals of the sampling interval, and the sampling interval is longer than the target time. And it is characterized in that it a.

  [Operation / Effect] The configuration of the present invention stores the sampling interval and the start time. The detection data relating to the detection of radiation output from the detector ring is stored in the detection data storage means. A tomographic image is generated based on this detection data. Specifically, the tomographic image generation unit generates a tomographic image using the target data group related to the tomographic image to be generated currently among the detection data group stored in the detection data storage unit. This target data group is a group of detection data arranged in the order detected by the detector ring. Moreover, the configuration of the target data group changes every time a tomographic image is generated, and accordingly, N different tomographic images are generated. First, the time information is referred to, and among the detection data stored in the detection data storage means, the detection data detected by the detector ring after the start time is recognized as the target data group. Then, this target data group is sent to the tomographic image generation means, and a tomographic image is generated. Thereafter, the start time is reset to a time later by the sampling interval. Then, the next tomographic image is generated. In this way, a series of tomographic images in which the subject images separated from each other by the sampling interval are reflected by cyclically repeating the recognition of the target data group, the generation of the tomographic image, and the setting of the start time point. Can be generated. Note that the sampling interval described above can be freely changed. According to the conventional configuration, since there is no concept of sampling interval and a tomographic image is generated after detection data is accumulated, such a change cannot be made.

  In the conventional configuration, the detection data detected by the detector ring at a certain point of time is only used for generating a single tomographic image, whereas in the present invention, a plurality of detection data at a certain point of time is used. Used to generate a tomographic image. That is, two target data groups adjacent to each other over time overlap each other over time, and each detection data is read from the detection data storage unit a plurality of times. Therefore, the total number of detection data used for the tomographic image can be increased, and a larger number of tomographic images can be acquired by one inspection. That is, according to the present invention, a series of tomographic images in which a subject image is captured at a time interval shorter than before can be generated, and a radiation tomography apparatus suitable for radiopharmaceutical follow-up inspection can be provided.

  The detection data is determined to be included in any target data group based on the time point detected by the detector ring. According to the above-described configuration, since the detection data and the time information are associated with each other, the time point detected by the detector ring of the detection data can be easily known.

  Moreover, the radiation tomography apparatus of the structure of this invention has memorize | stored object time. The target time determines the time length of the target data group. According to the above-described configuration, the target data group is configured by detection data detected within one section with time. The start of the interval is the start time, and the end is the time after the start time. For example, if the time width of the target data group is too long with respect to the change rate of the distribution of the drug, the drug distribution reflected in the tomographic image is blurred. According to the above-described configuration, it can be reduced.

  Further, the sampling interval of the present invention is less than the target time. Thereby, detection data acquired at a certain time is used when constructing a plurality of radiation tomographic images. That is, since the total number of detection data at the time of constructing the radiation tomographic image can be increased, the radiation tomographic image becomes clear. In addition, since the sampling interval can be set without being limited by the target time, the change in the drug distribution can be reliably traced by making the sampling interval shorter.

The invention according to claim 2 is the radiation tomography apparatus according to claim 1, further comprising input means for inputting an operator's instruction, and parameters stored in the target time storage means or the sampling interval storage means . Is characterized in that it can be changed by the input means.

  [Operation / Effect] According to the above-described configuration, for example, the sampling interval and the target time can be changed based on the operator's designation. As a result, since the mode of generation of the tomographic image can be changed in accordance with the behavior of the radiopharmaceutical in the subject, a radiation tomography apparatus more suitable for the radiopharmaceutical follow-up examination can be provided.

  According to a third aspect of the present invention, in the radiation tomography apparatus according to the first aspect, in addition to the operations (A), (B), and (C), the determining means is (D1) from the target time storage means. The length of the target time that is repeatedly read out by the determination means and is successively read by the determination means is equal to or longer than the length of the target time read by the determination means last time.

  [Operation / Effect] According to the above-described configuration, a clearer tomographic image can be provided. That is, the dose of radiation emitted from the radiopharmaceutical becomes maximum immediately after being administered to the subject, and then gradually decreases. The above-described configuration increases the length of the target time in accordance with the resetting of the start time. In other words, the more tomographic images that have elapsed since the medication, the more tomographic images are generated based on groups of detection data over a longer period of time. Therefore, even if the detection frequency of the radiation detected by the detector ring decreases as time elapses from medication, a tomographic image at the time when time elapses from medication is generated based on a sufficient number of detection data. The Therefore, the acquired tomographic image becomes clearer.

In addition, the present invention can take the following configurations in order to solve the above-described problems.
That is, the radiation tomography apparatus according to claim 4 is configured such that the radiation detectors for detecting radiation are arranged in a ring shape, the detector ring for outputting detection data, the detection data, and the radiation at which point. Detection data storage means for storing time information indicating whether it has been detected, tomographic image generation means for reading out a part of the detection data group stored in the detection data storage section and generating a radiation tomographic image, and tomographic image generation means The radiation tomography using a determination means for determining which detection data is to be read from the detection data storage unit in the detection data group, and detection data indicating radiation detected by the detector ring during a certain period when creating an image, a start time storage means for storing a start time that indicates the beginning of the period, the target number storage for storing a number of subjects exhibiting a score of the detected data Shows the stage, and the target time setting value acquisition unit number of the detected data included in the target time to determine target time so that the number of target, the spacing of each of the starting point in the time series adjacent radiation tomographic image Sampling interval storage means for storing the sampling interval, and the determination means detects within the target time from the start point of the detection data stored in the detection data storage means with reference to (A) time information. The detection data detected by the instrument ring is recognized as a target data group used when generating a radiation tomographic image, (B) the target data group is sent to the tomographic image generation means, and (C) a sampling interval after the start time By repeating the operations (A), (B), and (C) that are reset as the next starting time, the sampling interval is set in the tomographic image generating means. Over time to produce a continuous series of radiological images the image is fancy-through was, sampling interval, it is characterized in that it is less subject hours.

  [Operation / Effect] According to the above-described configuration, the number of objects is set. And all the detection data used when producing | generating the tomographic image acquired are the same number (object number). Thereby, a clearer image may be acquired rather than acquiring a tomographic image while lengthening target time.

  The invention described in claim 5 is the radiation tomography apparatus according to any one of claims 1 to 4, further comprising a top plate extending in the central axis direction and inserted into the detector ring. In addition to this, (α) a radiation source that can rotate around the central axis relative to the top plate, (β) a radiation detection means that can rotate around the central axis relative to the top plate, and (γ) a radiation source, The image generation apparatus further includes a support unit that supports the radiation detection unit, (δ) a rotation unit that rotates the support unit, and (ε) a rotation control unit that controls the rotation unit. is there.

  [Operation / Effect] According to the above-described configuration, it is possible to provide a radiation tomography apparatus capable of acquiring both the internal structure of the subject and the drug distribution. A PET device can generally obtain information relating to drug distribution. However, it may be necessary to make a diagnosis while referring to a tomographic image in which an organ or tissue of the subject is captured. According to the above-described configuration, since both the internal structure of the subject and the drug distribution can be acquired, for example, by superimposing both images, a composite image suitable for diagnosis can be generated.

  The tomographic image generation means of the present invention generates a tomographic image using the target data group related to the tomographic image to be generated at present among the detection data group stored in the detection data storage means. Specifically, it is as follows. First, the time information is referred to, and among the detection data stored in the detection data storage means, the detection data detected by the detector ring after the start time is recognized as the target data group. Then, this target data group is sent to the tomographic image generation means, and a tomographic image is generated. Thereafter, the start time is reset to a time later by the sampling interval. Then, the next tomographic image is generated. In this way, a series of tomographic images in which the subject images separated from each other by the sampling interval are reflected by cyclically repeating the recognition of the target data group, the generation of the tomographic image, and the setting of the start time point. Can be generated.

  In addition, the detection data detected by the detector ring at a certain point in the conventional configuration is only used for generating a single tomographic image, whereas the detection data at a certain point in the present invention is Used to generate a plurality of tomographic images. That is, the total number of detection data that can be used for the tomographic image can be increased, and a series of tomographic images in which the subject image is captured can be generated at a shorter time interval than in the past.

1 is a functional block diagram illustrating a configuration of a radiation tomography apparatus according to Embodiment 1. FIG. 1 is a perspective view illustrating a configuration of a radiation detector according to Embodiment 1. FIG. It is a figure explaining the structure of the detector ring which concerns on Example 1. FIG. FIG. 3 is a schematic diagram illustrating detection of radiation according to the first embodiment. 1 is a functional block diagram illustrating a configuration of a radiation tomography apparatus according to Embodiment 1. FIG. 6 is a schematic diagram illustrating generation of a tomographic image according to Embodiment 1. FIG. 6 is a schematic diagram illustrating generation of a tomographic image according to Embodiment 1. FIG. 6 is a schematic diagram illustrating generation of a tomographic image according to Embodiment 1. FIG. FIG. 10 is a schematic diagram illustrating generation of a tomographic image according to the second embodiment. FIG. 9 is a functional block diagram illustrating a configuration of a radiation tomography apparatus according to Embodiment 3. It is a top view explaining the structure of the radiation tomography apparatus of a conventional structure. It is a functional block diagram explaining the structure of the radiation tomography apparatus of a conventional structure. It is a schematic diagram explaining the production | generation of the tomographic image of a conventional structure.

  The best mode of the calibration data collection method in the radiation tomography apparatus according to the present invention will be described below. In addition, the gamma ray demonstrated below is an example of the radiation of this invention. In the first and second embodiments, the present invention is applied to a PET apparatus, and in the third embodiment, the present invention is applied to a PET / CT apparatus.

<Overall configuration of radiation tomography apparatus>
Embodiments of the radiation tomography apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a functional block diagram illustrating the configuration of the radiation tomography apparatus according to the first embodiment. As shown in FIG. 1, the radiation tomography apparatus 9 according to the first embodiment includes a top plate 10 for supine the subject M and a gantry 11 having a through hole surrounding the subject M. The top plate 10 is provided so as to pass through the opening of the gantry 11 and is movable back and forth along the direction in which the opening of the gantry 11 extends (z direction). Such sliding of the top plate 10 is realized by the top plate moving mechanism 15. The top plate moving mechanism 15 is controlled by the top plate movement control unit 16.

  Inside the gantry 11 is provided a detector ring 12 for detecting an annihilation gamma ray pair emitted from the subject M. The detector ring 12 has a cylindrical shape extending in the body axis direction z (corresponding to the extending direction of the present invention) of the subject M, and the length is 1 m to 1.8 m. That is, the detector ring 12 extends to such an extent that at least the body portion of the subject M can be completely covered.

  The detector ring 12 is configured by arranging block-shaped radiation detectors 1 in a ring shape. If the width per one in the radiation detector 1 is about 5 cm, about 20 to 36 radiation detectors 1 are arranged on the detector ring 12 in the z direction. The configuration of the radiation detector 1 will be briefly described. FIG. 2 is a perspective view illustrating the configuration of the radiation detector according to the first embodiment. As shown in FIG. 2, the radiation detector 1 includes a scintillator 2 that converts radiation into fluorescence, and a photodetector 3 that detects fluorescence. A light guide 4 for transmitting and receiving fluorescence 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 Lu _{2 (1-X)} Y _2X SiO ₅ (hereinafter referred to as LYSO ₎ in which Ce is diffused. The photodetector 3 can specify the fluorescence generation position indicating which scintillator crystal emits fluorescence, and can also specify the intensity of fluorescence and the time when the fluorescence is generated. it can. The scintillator crystal corresponds to the radiation detection element of the present invention.

  The configuration of the detector ring 12 will be described. FIG. 3 is a diagram illustrating the configuration of the detector ring according to the first embodiment. The radiation detectors 1 are arranged in an annular shape along a regular polygonal shape in the detector ring 12. Then, the scintillator crystals are also arranged along the virtual circle to constitute a unit detection ring 12b as shown in FIG. The unit detection ring 12b is formed of scintillator crystals C (radiation detection elements) arranged at the same position in the z direction and arranged along an annular ring. That is, the unit detection ring 12b is a concept in which scintillator crystals are arranged in a line and is independent of the radiation detectors 1 arranged along a virtual circle. As shown in FIG. 3B, the unit detection ring 12b is connected in the z direction to form the detector ring 12. In other words, the unit detection rings 12b are connected to share a central axis along the z direction. The unit detection ring 12b has a through-hole at the center, and the unit detection ring 12b is arranged so that the through-holes of the unit detection ring 12b are connected, and the detector ring 12 is configured. You can also.

  According to the first embodiment, the detector ring 12 is formed by arranging around 100 radiation detectors 1 in an annular shape. Therefore, when the through hole 12a is viewed from the z direction, the through hole 12a is, for example, It is a regular 100-gon. In this case, the plurality of unit detection rings 12b are connected so as to share the respective central axes, and the through hole 12a has a shape of a 100 prism.

  The radiation tomography apparatus 9 according to the first embodiment is further provided with each unit for acquiring a tomographic image of the subject M as shown in FIG. Specifically, the radiation tomography apparatus 9 receives, from the detection data detected by the detector ring 12, a filter unit 20 that extracts valid data, and data that is regarded as valid by the filter unit 20. A fluorescence intensity acquisition unit 21 that acquires the fluorescence intensity of the annihilation γ-ray pair, a LOR specification unit 22 that specifies the incident position of the annihilation γ-ray pair in the detector ring 12, a data storage unit 23 that stores detection data, A mapping unit 24 that forms a tomographic image of the subject M, and a determination unit 26 that determines which detection data to be read out of the detection data group stored in the data storage unit 23 with respect to the mapping unit 24; And a calibration unit 25 for calibrating the tomographic image of the subject M. The calibration unit 25 refers to the calibration data stored in the calibration data storage unit 34 and removes the false image reflected in the tomographic image. The set value storage unit 27 stores various set values (set values related to the sampling interval, start time, and target time), which will be described later.

  The LOR (Line of Response) specifying unit corresponds to the incident position acquisition means of the present invention. The data storage unit corresponds to the detection data storage unit of the present invention, and the mapping unit corresponds to the tomographic image generation unit of the present invention. The determination unit corresponds to the determination unit of the present invention, and the input unit corresponds to the input unit of the present invention.

  Further, the radiation tomography apparatus 9 according to the first embodiment includes a main control unit 35 that performs overall control of each unit and a display unit 36 that displays a radiation tomographic image. The main control unit 35 is constituted by a CPU or the like, and executes various programs to thereby obtain a filter unit 20, a fluorescence intensity acquisition unit 21, a LOR specifying unit 22, a mapping unit 24, a calibration unit 25, a determination unit 26, and the like. Is realized. In addition, each above-mentioned part may be divided | segmented and implement | achieved by the control apparatus which takes charge of them.

<Operation of radiation tomography system>
Next, the operation of the radiation tomography apparatus having such a configuration will be described. First, the subject M to which the radiopharmaceutical is injected is placed on the top board 10. The top plate 10 moves according to the control of the top plate movement control unit 16, and the subject M is introduced into the gantry 11. At this time, the imaging range of the subject M is positioned inside the detector ring 12. During the detection of radiation irradiated from the subject M, the top 10 does not move.

  When an annihilation gamma ray pair is generated from the subject M, the annihilation radiation pair enters two different scintillator crystals of the detector ring 12. The fluorescence generated from the scintillator crystal is detected by the photodetector 3, and detection data is output. On the other hand, clock data, which is time information, is sent from the clock 19 to the detector ring 12. This clock data is, for example, a serial number. This clock data is added to the detection data. The assigned clock data indicates when the radiation is detected and corresponds to time information of the present invention.

  When the annihilation radiation pair enters the detector ring 12, two independent detection data are output from the detector ring 12. If two detection data are obtained within a predetermined time range, they are paired and derived from a single annihilation radiation pair. And the detection data whose partner is not found within the time range are discarded before the process related to pairing.

  The LOR specifying unit 22 specifies an LOR that is a line segment connecting two scintillator crystals. That is, it is a line segment that connects different scintillator crystals that are considered to have been incident with γ rays simultaneously by emitting fluorescence during a period within a predetermined time window. The detection data output from the detector ring 12 includes position data indicating which scintillator crystal is used. The LOR specifying unit 22 obtains the LOR from the two detection data that are considered to be due to the annihilation radiation pair. The detection data output from the LOR specifying unit 22 is stored in the data storage unit 23. In this way, the data storage unit 23 stores a large number of detection data. The entire detection data acquired by detecting a series of annihilation γ-ray pairs will be referred to as a detection data group.

  If each of the detection data constituting the detection data group is arranged and compared in the order of the detected time series, the movement of the radiopharmaceutical in the subject M can be known. For example, as shown in FIG. 4, it is assumed that the medicine is at point P at the first time point, the medicine has moved from there, and has moved to point Q at the second time point. Of the detection data group stored in the data storage unit 23, the LOR in the detection data detected at the first time point increases that passes through the point P. Similarly, many of the LORs in the detection data detected at the second time point pass through the point Q. Therefore, intuitively, if the tomographic image is acquired using only the detection data detected at the first time point, it is likely that the temporary distribution of the radiopharmaceutical can be clearly identified.

  However, in practice, when such a tomographic image is obtained, the detection data is insufficient and the drug distribution cannot be sufficiently mapped, and the tomographic image becomes blurred. Therefore, in order to prevent this, a sufficient amount of detection data for generating a tomographic image is accumulated, and a tomographic image is generated based on these. That is, in order to acquire tomographic images that are continuous over time, it is necessary to extract only detection data collected during a predetermined period from the detection data group and send it to the mapping unit 24.

  The selection unit 26 selects such detection data. The determination unit 26 sends detection data to the mapping unit 24 while referring to various setting values stored in the setting value storage unit 27. As shown in FIG. 5, the set value storage unit 27 includes a sampling interval storage unit 27a, a start point storage unit 27b, a target time storage unit 27c, and an overwrite count storage unit 27d. Hereinafter, the operation of the determination unit 26 will be described assuming that a series of tomographic images in which the radiopharmaceutical distribution is reflected is generated in time series. When generating the tomographic image, the determination unit 26 reads the start time setting value S and the target time setting value Wa stored in each storage unit. The sampling interval storage unit corresponds to the sampling interval storage means of the present invention. The start time storage unit corresponds to the start time storage unit of the present invention, and the target time storage unit corresponds to the target time storage unit of the present invention. The start time set value is a specific example of the start time of the present invention.

  Next, the determination unit 26 recognizes the target data group. FIG. 6 is a schematic diagram illustrating generation of a tomographic image according to the first embodiment. In FIG. 6, D indicates detection data arranged in time series based on the clock data, and G indicates a detection data group. Ds is detection data corresponding to detection data detected at the start point indicated by the start point set value S. The start time setting value S indicates the detection data located at the top of the detection data group G in time series. The determination unit 26 recognizes the target data group based on the detection data detected by the detector ring 12 within the target time Wa from the start point indicated by the start point set value S. The target data group at this time is twelve detection data that are within the target time Wa and that are continuous in time series with the detection data Ds as the head. The determination unit 26 sends each detection data belonging to the target data group to the mapping unit 24. The mapping unit 24 generates a tomographic image P1 based on the target data group. As described above, the start time setting value S indicates the beginning of a period when a radiation tomographic image is created using detection data indicating radiation detected by the detector ring during a certain period. The target time Wa indicates the length of a period when a radiation tomographic image is created using detection data indicating radiation detected by the detector ring 12 during a certain period.

  Next, the determination unit 26 overwrites and resets the start time set value S stored in the start time storage unit 27b. Specifically, the start point set value S is reset to a point after the sampling interval Wb. In FIG. 7, since the start time set value S is changed, the start time set value S indicates detection data on the back side by five detection data continuous in time series from the detection data Ds in FIG. 6. become.

  The determination unit 26 recognizes a target data group from detection data detected by the detector ring 12 during the target time Wa from the start time indicated by the start time set value S. The target data group at this time is twelve detection data items that fall within the target time Wa in FIG. The determination unit 26 sends each detection data belonging to the target data group to the mapping unit 24. The mapping unit 24 generates a tomographic image P2 based on the target data group. Each of the tomographic image P1 and the tomographic image P2 represents a radiation tomographic image separated in time series by the sampling interval Wb. Thus, the sampling interval Wb means the time interval between adjacent radiation tomographic images in time series. The target time Wa means a temporal spread of detection data used when constructing a radiation tomographic image.

  In Example 1, as shown in FIG. 8, the sampling interval Wb is equal to or less than the target time Wa. Thereby, detection data acquired at a certain time is used when constructing a plurality of radiation tomographic images. That is, since the total number of detection data at the time of constructing the radiation tomographic image can be increased, the radiation tomographic image becomes clear. Further, the sampling interval Wb can be set without being limited by the target time Wa. By making the sampling interval Wb shorter, changes in the drug distribution can be reliably traced.

  Thereafter, similarly, the determination unit 26 repeats the recognition of the target data group, the transmission of the target data group to the mapping unit 24, and the change of the start time set value S. In this way, as shown in FIG. 8, a series of tomographic images P1 to P5 in which radiation tomographic images separated in time series by the sampling interval Wb can be obtained. During this time, the starting point set value S is overwritten several times. Each time the determination unit 26 overwrites the start point set value S, the determination unit 26 stores the overwrite number N of the start point set value S in the overwrite number storage unit 27d. The series of tomographic images are displayed on the display unit 36 after the false image removal process is performed by the calibration unit 25. Thus, the acquisition of the radiation tomographic image according to the first embodiment is completed.

  As described above, the configuration of the first embodiment stores the sampling interval Wb and the start time setting value S. Then, the mapping unit 24 generates a tomographic image using the target data group related to the tomographic image to be generated among the detected data groups stored in the data storage unit 23. This target data group is a group of detection data arranged in the order detected by the detector ring 12. Moreover, the configuration of the target data group is different each time a tomographic image is generated. A specific method for generating a tomographic image using the detection data group is as follows. First, the determination unit 26 refers to the clock data associated with each of the detection data, and the detection ring 12 detects the detection data stored in the data storage unit 23 after the start time set value S. The detection data is recognized as a target data group. Then, the target data group is sent to the mapping unit 24, and a tomographic image is generated. Thereafter, the start time setting value S is reset to a time point later by the sampling interval Wb. Then, the mapping unit 24 generates the next tomographic image. In this way, by repeating each of the recognition of the target data group, the generation of the tomographic image, and the setting of the start time set value S, the subject images separated from each other over time by the sampling interval Wb are reflected. A series of tomographic images can be generated.

  In addition, the detection data detected by the detector ring 12 at a certain point in the conventional configuration is only used to generate a single tomographic image, whereas the detection at a certain point in the first embodiment is performed. The data is used to generate a plurality of tomographic images. That is, two target data groups that are adjacent over time overlap with time. Therefore, the total number of detection data that can be used for the tomographic image can be increased, and a larger number of tomographic images can be acquired by one inspection. That is, according to the configuration of the first embodiment, it is possible to generate a series of tomographic images in which a subject image is captured at a time interval shorter than before, and to provide a radiation tomography apparatus 9 suitable for a radiopharmaceutical follow-up examination.

  The detection data is determined to be included in any target data group based on the time point detected by the detector ring 12. According to the above-described configuration, since the detection data and the clock data are associated with each other, the time point when the detection data is detected by the detector ring 12 can be easily known.

  The radiation tomography apparatus 9 having the configuration of the first embodiment stores the target time Wa. This target time Wa determines the time length of the target data group. According to the configuration of the first embodiment, the target data group is configured by detection data detected within one section with time. The start of the section is the start time set value S, and the end is the time after the start time set value S by the target time Wa. If the time width of the target data group is too long, the drug distribution reflected in the tomographic image is blurred. According to the above-described configuration, it can be prevented.

  Further, according to the above-described configuration, the sampling interval Wb and the target time can be changed based on the operator's designation. As a result, the mode of generation of the tomographic image can be changed in accordance with the behavior of the radiopharmaceutical in the subject, so that the radiation tomography apparatus 9 more suitable for the radiopharmaceutical follow-up inspection can be provided.

  Next, a radiation tomography apparatus according to Embodiment 2 will be described. Since the configuration of the radiation tomography apparatus 9 according to the second embodiment is the same as that of the first embodiment, the description thereof is omitted. The configuration of the second embodiment differs from the first embodiment in the configurations of the target time storage unit 27c and the determination unit 26.

  The target time storage unit 27c stores a target time table in which the target time and the serial number are associated. Then, the determination unit 26 reads and uses one of the target times listed in the target time table. The determination unit 26 reads the target time when overwriting and resetting the start time set value S stored in the start time storage unit 27b. Therefore, every time a tomographic image is generated, the target time stored in the target time storage unit 27c is referred to.

  The determination unit 26 changes the read target time according to the number of times of overwriting the start time set value S. Specifically, one of the target times listed in the target time table is selected by comparing the number of overwritings with the serial number of the target time table.

  The dose of the annihilation radiation pair irradiated from the subject M is generally the highest at the start of the examination and then gradually weakens. Therefore, if it is desired to acquire a tomographic image after a considerable time has elapsed since the start of the examination, sufficient detection data necessary for acquiring the tomographic image cannot be obtained unless the target time is increased. In the configuration of the second embodiment, for the purpose of solving such a problem, the determination unit 26 increases the read target time Wa as the operation is repeated. At this time, the target time set value Wa may be configured such that the user sets an arbitrary value, or may be automatically obtained from the half-life of the radiopharmaceutical. The derivation of the target time set value Wa is performed by the target time set value acquisition unit 37.

  The operation of the determination unit 26 will be described with reference to FIG. The target data group used to generate the tomographic image P1 is detection data continuous in time series that falls within the target time Wa1. On the other hand, when generating the tomographic image P2, the target time Wa2 is used. The lengths of both target times Wa1, Wa2 at this time are the same. However, the tomographic image P3 is generated based on the target time Wa3 whose length is longer than that of the target image Wa2. Thereafter, similarly, the lengths of the target times Wa4 to Wa7 based on the generation of the tomographic image P4 to the tomographic image P7 become longer as the code becomes larger.

  Moreover, it should be noted that the sampling interval Wb is constant regardless of the change in the length of the target time Wa. In this way, it is possible to acquire tomographic images P1 to P7 that are continuous in time series with a certain time interval.

  Note that the target time set value acquisition unit 37 described above may determine the interval of the target time Wa so that the points of the detection data included in the target time Wa are the same. Assuming that the target times Wa obtained in this way are Wa1 to Wa7 in FIG. 9, the scores of the detection data included in each of the target times Wa1 to Wa7 are the same number, that is, the number of targets. It is. Moreover, the target time set value acquisition unit 37 acquires Wa1 to Wa7 during the inspection. For example, when seven frames (images) are to be acquired, there is a problem that it is unclear at which stage the last target time Wa7 is completed, and it is not known at which point the inspection should be completed. In order to solve such a problem, the target time set value acquisition unit 37 waits until the number of detection data constituting the seventh frame image reaches a predetermined number. Meanwhile, the target time set value acquisition unit 37 sends to the main control unit 35 that the number of detection data points is insufficient to construct the seventh frame image. Then, the main control unit 35 extends the inspection time and continues the inspection until the detection data score becomes sufficient. Note that the target number indicating the number of detection data points per frame is stored in the set value storage unit 27. The set value storage unit 27 corresponds to the target number storage unit of the present invention.

  That is, when each frame is generated, the number of target data constituting the target data group read one after another by the determination unit 26 is the number of targets read by the determination unit 26 from the set value storage unit 27.

  According to the configuration of the second embodiment, a tomographic image with more stable image quality can be provided. That is, the dose of radiation emitted from the radiopharmaceutical is maximized immediately after being administered to the subject M, and then gradually decreases. In the above-described configuration, the length of the target time Wa is increased as the start time set value S is reset. In other words, the more tomographic images that have elapsed since the medication, the more tomographic images are generated based on groups of detection data over a longer period of time. Therefore, even when the detection data output from the detector ring 12 decreases as time elapses from the medication, the tomographic image at the time when the time has elapsed since the medication is generated based on the sufficient number of detection data. The Therefore, the acquired tomographic image becomes more stable in image quality.

  Next, a PET / CT apparatus according to Example 3 will be described. The PET / CT apparatus has a configuration including the radiation tomography apparatus (PET apparatus) 9 described in the first and second embodiments and a CT apparatus that generates a tomographic image using X-rays. This is a medical device that can generate a composite image obtained by superimposing the tomographic images.

  A configuration of the PET / CT apparatus according to the third embodiment will be described. In the PET apparatus in the PET / CT apparatus according to the third embodiment, the radiation tomography apparatus (PET apparatus) 9 described in the first or second embodiment can be used. Therefore, a CT apparatus which is a characteristic part in the third embodiment will be described. As shown in FIG. 10, the CT apparatus 8 has a gantry 45. The gantry 45 is provided with an opening extending in the z direction, and the top plate 10 is inserted into the opening.

  An gantry 45 supports an X-ray tube 43 that irradiates the subject with X-rays, an FPD (flat panel detector) 44 that has passed through the subject, and the X-ray tube 43 and the FPD 44. A support 47 is provided. The support 47 has a ring shape and is rotatable around the z axis. The rotation of the support 47 is performed by a rotation mechanism 39 including a power generation unit such as a motor and a power transmission unit such as a gear. The rotation control unit 40 controls the rotation mechanism 39. The X-ray tube corresponds to the radiation source of the present invention. The FPD corresponds to the radiation detection means of the present invention, and the support corresponds to the support means of the present invention. The rotation mechanism corresponds to the rotation means of the present invention, and the rotation control unit corresponds to the rotation control means of the present invention.

  The CT image generation unit 41 generates an X-ray tomographic image of the subject M based on the X-ray detection data output from the FPD 44. The superimposing unit 42 generates a superposition image by superimposing the PET image indicating the drug distribution in the subject output from the radiation tomography apparatus (PET apparatus) 9 and the above-described X-ray tomographic image. It has a configuration.

  The main control unit 35 executes various programs to thereby determine the rotation unit 40, the CT image generation unit 41, the determination unit 26 according to the first and second embodiments, the mapping unit 24, the calibration unit 25, and the like. An overlapping unit 42 and an X-ray tube control unit 46 are realized. In addition, each above-mentioned part may be divided | segmented and implement | achieved by the control apparatus which takes charge of them.

  A method for acquiring a fluoroscopic image will be described. The X-ray tube 43 and the FPD 44 rotate around the z axis while maintaining their relative positions. At this time, the X-ray tube 43 intermittently irradiates the subject M with X-rays, and each time the CT image generation unit 41 generates an X-ray fluoroscopic image. The plurality of fluoroscopic images are assembled into a single tomographic image using the existing back projection method in the CT image generation unit 41, for example.

  Next, a method for generating a composite image will be described. In order to acquire a composite image with the PET / CT apparatus, a region of interest of the subject M is introduced into the CT apparatus, and an X-ray tomographic image thereof is acquired. In addition to this, a region of interest of the subject M is introduced into a radiation tomography apparatus (PET apparatus) 9 to acquire a PET image. Both images are superimposed by the overlapping unit 42, and the completed composite image is displayed on the display unit 36. Thereby, since the drug distribution and the internal structure of the subject can be recognized simultaneously, a tomographic image suitable for diagnosis can be provided.

  According to the configuration of the third embodiment, the radiation tomography apparatus 9 that can acquire both the internal structure of the subject M and the drug distribution can be provided. A PET device can generally obtain information relating to drug distribution. However, it may be necessary to make a diagnosis while referring to a tomographic image in which an organ or tissue of the subject M is captured. According to the above configuration, since both the internal structure of the subject M and the drug distribution can be acquired, for example, a composite image suitable for diagnosis can be generated by superimposing both images.

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

(1) The scintillator crystal referred to in each of the above embodiments is composed of LYSO. However, in the present invention, the scintillator crystal is composed of other materials such as GSO (Gd ₂ SiO ₅ ) instead. Also good. According to this modification, it is possible to provide a method of manufacturing a radiation detector that can provide a cheaper radiation detector.

  (2) In each of the embodiments described above, the fluorescence detector is composed of a photomultiplier tube, but the present invention is not limited to this. Instead of the photomultiplier tube, a photodiode, an avalanche photodiode, a semiconductor detector, or the like may be used.

  (3) In each of the embodiments described above, the top plate is slidable. However, the present invention is not limited to this. For example, the top plate may be fixed and the gantry 11 may slide.

  (4) In each embodiment described above, the time information is associated with the detection data. However, the present invention is not limited to this, and the association may not be performed. That is, the time information may be continuously sent from the clock 19 to the filter unit 20, and the detection data may be sent to the filter unit 20 together with the time information as soon as it is output. The filter unit 20 acquires a data group in which detection data and time information are mixed, and based on this, it is possible to determine when the detection data is output from the detector ring 12. .

  (5) Further, in each of the above-described embodiments and the above-described modifications, the clock 19 may be realized by software. That is, first, a predetermined time width (for example, 128 ns) is determined. The detector ring 12 sends only one detection data to the filter unit 20 during a specified time width, and when there is no detection data to be sent during the next specified time width, it indicates that there is no detection data. The dummy data shown is sent out. The filter unit 20 counts the dummy data and the detection data without discrimination (hereinafter simply referred to as data), and counts the number of data points to determine when the detection data is output from the detector ring 12. It is a structure to know. The prescribed time width is stored in the set value storage unit 27.

  As described above, the present invention is suitable for a medical radiation tomography apparatus.

DESCRIPTION OF SYMBOLS 1 Radiation detector 9 Radiation tomography apparatus 10 Top plate 12 Detector ring 21 Fluorescence intensity acquisition part (radiation intensity acquisition means)
22 LOR specific part (incident position acquisition means)
23 Data storage unit (detection data storage means)
24 Mapping unit (tomographic image generating means)
26 Determination unit (determination means)
27a Sampling interval storage unit (sampling interval storage means)
27b Start time storage section (start time storage means)
27c Target time storage unit (target time storage means)
38 Input section (input means)
39 Rotating mechanism (rotating means)
40 Rotation control unit (rotation control means)
43 X-ray tube (radiation source)
44 FPD (radiation detection means)
47 Support (support means)

Claims (5)

A radiation detector for detecting radiation is arranged in a ring shape, and a detector ring for outputting detection data;
Detection data storage means for storing detection data and time information indicating when radiation was detected;
A tomographic image generating means for reading out a part of the detection data group stored in the detection data storage unit and generating a radiation tomographic image;
A determination unit that determines which detection data of the detection data group is read from the detection data storage unit to the tomographic image generation unit;
Start time storage means for storing a start time indicating the beginning of the period when creating a radiation tomographic image using detection data indicating the radiation detected in the detector ring during a period;
A target time storage means for storing a target time indicating the length of the period;
Sampling interval storage means for storing a sampling interval indicating an interval of each of the start time points in radiation tomographic images adjacent in time series,
The determination means is (A) detection data stored in the detection data storage means with reference to the time information and detected by the detector ring within the target time starting from the start time. As a target data group used when generating a radiation tomographic image,
(B) sending the target data group to the tomographic image generation means;
(C) By repeating the operations (A), (B), and (C) of resetting the time point after the start time point by the sampling interval as the next start time point, the tomographic image generating unit is caused to perform the sampling. Generate a series of radiation tomographic images in which continuous images are captured over time at intervals,
The radiation tomography apparatus according to claim 1, wherein the sampling interval is equal to or shorter than the target time. The radiation tomography apparatus according to claim 1,
It further comprises an input means for inputting an instruction of the surgeon,
The radiation tomography apparatus according to claim 1, wherein the parameter stored in the target time storage means or the sampling interval storage means can be changed by the input means. The radiation tomography apparatus according to claim 1,
In addition to the operations (A), (B), and (C), the determination unit repeatedly (D1) reads the target time from the target time storage unit,
The length of the target time read one after another by the determining means is equal to or longer than the length of the target time read by the determining means last time. A radiation detector for detecting radiation is arranged in a ring shape, and a detector ring for outputting detection data;
Detection data storage means for storing detection data and time information indicating when radiation was detected;
A tomographic image generating means for reading out a part of the detection data group stored in the detection data storage unit and generating a radiation tomographic image;
A determination unit that determines which detection data of the detection data group is read from the detection data storage unit to the tomographic image generation unit;
Start time storage means for storing a start time indicating the beginning of the period when creating a radiation tomographic image using detection data indicating the radiation detected in the detector ring during a period;
Object number storage means for storing the object number indicating the score of the detection data ;
Target time setting value acquisition means for determining the target time so that the number of detection data included in the target time becomes the target number;
Sampling interval storage means for storing a sampling interval indicating an interval of each of the start time points in radiation tomographic images adjacent in time series,
The determination means is (A) detection data stored in the detection data storage means with reference to the time information and detected by the detector ring within the target time starting from the start time. As a target data group used when generating a radiation tomographic image,
(B) sending the target data group to the tomographic image generation means;
(C) By repeating the operations (A), (B), and (C) of resetting the time point after the start time point by the sampling interval as the next start time point, the tomographic image generating unit is caused to perform the sampling. Generate a series of radiation tomographic images in which continuous images are captured over time at intervals,
The radiation tomography apparatus according to claim 1, wherein the sampling interval is equal to or shorter than the target time. The radiation tomography apparatus according to any one of claims 1 to 4,
Further comprising a top plate extending in the central axis direction of the detector ring and inserted therein, in addition to this,
(Α) a radiation source rotatable about the central axis with respect to the top plate;
(Β) a radiation detection means rotatable around the central axis with respect to the top plate;
(Γ) a support means for supporting the radiation source and the radiation detection means;
(Δ) rotating means for rotating the support means;
(Ε) A radiation tomography apparatus further comprising an image generation apparatus including a rotation control unit that controls the rotation unit.

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