JP7214355B2 - Positron emission tomography system - Google Patents

Description

Embodiments of the present invention relate to a positron emission tomography apparatus.

2. Description of the Related Art Conventionally, in the medical field, a positron emission tomography (PET) apparatus is known as one of medical image diagnostic apparatuses used for functional diagnosis of living tissue inside a subject. The PET apparatus coincidentally counts a pair of annihilation gamma rays emitted by pair annihilation of positrons generated from positron-emitting nuclides in the tracer administered to the subject with electrons in the subject. An apparatus for producing an image showing the distribution of a tracer in a

WO2011/125212 U.S. Patent Application Publication No. 2014/246594 U.S. Patent Application Publication No. 2005/249432

A problem to be solved by the present invention is to improve the spatial resolution of a PET apparatus.

A PET apparatus according to an embodiment includes a PET detector in which a plurality of detection elements are arranged in the circumferential direction and the central axis direction. In the PET detector, when the detecting element arranged in the central region in the central axis direction among the plurality of detecting elements is translated to each of the both end regions in the central axis direction, Detecting elements are arranged so as to obtain an LOR (Line Of Response) with a thickness smaller than that obtained by a pair of detecting elements positioned diagonally in .

FIG. 1 is a diagram showing a configuration example of a positron emission tomography apparatus according to the first embodiment. FIG. 2 is a diagram illustrating a configuration example of a detector module according to the first embodiment; FIG. 3 is a diagram showing a comparative example of the PET apparatus according to this embodiment. FIG. 4 is a diagram showing an example of LOR obtained by a pair of detection elements included in the PET detector according to this embodiment. FIG. 5 is a diagram showing a configuration example of a PET detector according to the first embodiment. FIG. 6 is a diagram showing another configuration example of the PET detector according to the first embodiment. FIG. 7 is a diagram showing a configuration example of a PET detector according to the second embodiment. FIG. 8 is a diagram showing a configuration example of a PET detector according to the third embodiment.

Hereinafter, embodiments of the positron emission tomography apparatus will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a configuration example of a positron emission tomography (PET) apparatus according to the first embodiment.

For example, as shown in FIG. 1, a PET device 100 according to this embodiment includes a gantry device 10 and a console 20. As shown in FIG.

The gantry device 10 detects pair annihilation gamma rays emitted from the subject P and collects count information about the detected pair annihilation gamma rays. Here, the gantry device 10 is formed with a cavity penetrating the gantry device 10 in the horizontal direction. This cavity serves as an imaging opening in which the subject P is placed when the subject P is imaged.

Specifically, the gantry device 10 includes a tabletop 11 , a bed device 12 , a bed driver 13 , a PET detector 14 and a counting information collection circuit 15 .

The top plate 11 is a bed on which the subject P is placed when the subject P is imaged. The bed device 12 movably supports the top board 11 . The bed driver 13 moves the tabletop 11 supported by the bed device 12 under the control of a bed control circuit 23, which will be described later.

The PET detector 14 detects pair annihilation gamma rays emitted from the subject P and outputs an electrical signal based on the detected pair annihilation gamma rays. Specifically, the PET detector 14 is formed in a cylindrical shape, and is arranged so as to surround an imaging aperture formed in the gantry device 10 . Here, the PET detector 14 has a plurality of detection elements arranged in the circumferential direction and the central axis direction. Detect pair annihilation gamma rays emitted in the surroundings.

For example, the PET detector 14 is composed of a plurality of detector modules 140 arranged in the circumferential direction and central axis direction of the PET detector 14 .

FIG. 2 is a diagram showing a configuration example of the detector module 140 according to the first embodiment.

For example, as shown in FIG. 2, in the PET detector 14 according to the present embodiment, a plurality of detector modules 140 are arranged in the circumferential direction (the direction of arrow D _C ) and the central axial direction (the direction of arrow D _A direction) are arranged side by side along each.

Here, for example, each detector module 140 is a photon-counting Anger-type detector, and includes a plurality of detector elements 141 arranged side by side in the circumferential direction and central axis direction of the PET detector 14, and a predetermined number of a plurality of photomultiplier tubes (PMTs) 142 arranged for each detector element 141 and a light guide 143 arranged between the detector element 141 and the PMT 142 .

The detection element 141 converts the annihilation gamma rays emitted from the subject P into scintillation photons (optical photons) and outputs the scintillation photons. For example, the detection element 141 is a scintillator formed of a scintillator crystal such as LaBr3 (Lanthanum Bromide), LYSO (Lutetium Yttrium Oxyorthosilicate), LSO (Lutetium Oxyorthosilicate), LGSO (Lutetium Gadolinium Oxyorthosilicate).

The PMT 142 multiplies the scintillation photons output from the detection element 141, converts them into electrical signals, and outputs the electrical signals.

Light guide 143 transmits scintillation photons output from detector element 141 to PMT 142 . For example, the light guide 143 is made of a plastic material or the like having excellent light transmittance.

In this way, each detector module 140 converts the pair annihilation gamma rays emitted from the subject P into scintillation photons by the detector element 141, converts the converted scintillation photons into electrical signals by the PMTs 142, and outputs the electrical signals.

Returning to FIG. 1, the count information collection circuit 15 is a processing circuit that collects count information on pair annihilation gamma rays detected by the PET detector 14 . Specifically, the count information collection circuit 15 converts the electrical signal output from the PET detector 14 into a digital signal by an A/D (Analog/Digital) converter, and detects the detected position and energy value of pair annihilation gamma rays. , and the time of detection. The count information collection circuit 15 then stores the generated list in the data storage circuit 24 .

For example, the count information collection circuit 15 identifies a plurality of PMTs 142 that have converted scintillation light into electrical signals at the same timing. Then, the count information collection circuit 15 calculates the position of the center of gravity using the identified position of each PMT 142 and the intensity of the electric signal, and identifies the detection element number indicating the position of the detection element 141 on which the pair annihilation gamma rays have entered. In addition, when the PMT 142 is a position detection type PMT, the PMT 142 may identify the position.

In addition, the count information collection circuit 15 identifies the energy value of the pair annihilation gamma rays incident on the detector module 140 by integrally calculating the intensity of the electrical signal output from each PMT 142 . Also, the count information collection circuit 15 identifies the detection time at which the pair annihilation gamma ray was detected by the detector module 140 . For example, the count information collection circuit 15 identifies the detection time with an accuracy of 10 ⁻¹² seconds (picoseconds). Note that the detection time may be an absolute time or an elapsed time from the start of imaging.

Then, the count information collection circuit 15 generates a count information list including the detection element number, energy value, and detection time for each detector module 140 and detection element 141 . For example, the count information collection circuit 15 collects count information such as "detection element number: P11, energy value: E11, detection time: T11" or "detection element number: P22, energy value: E22, detection time: T22." Generate a list. The count information collection circuit 15 then stores the generated count information in the data storage circuit 24 .

The console 20 receives various operations for the PET apparatus 100 from the operator, and controls the operation of the PET apparatus 100 based on the received operations.

Specifically, the console 20 includes an input interface 21, a display 22, a bed control circuit 23, a data storage circuit 24, a coincidence counting information generation circuit 25, an image reconstruction circuit 26, and a system control circuit 27. Prepare. Here, each unit included in the console 20 is connected via a bus.

The input interface 21 receives input operations of various instructions and various information from the operator. Specifically, the input interface 21 converts an input operation received from the operator into an electric signal and outputs the electric signal to the system control circuit 27 . For example, the input interface 21 includes a trackball, a switch button, a mouse, a keyboard, a touch pad for performing input operations by touching the operation surface, a display for setting imaging conditions and a region of interest (ROI), and the like. It is realized by a touch screen in which a screen and a touch pad are integrated, a non-contact input circuit using an optical sensor, an audio input circuit, and the like. In this specification, the input interface 21 is not limited to having physical operation parts such as a mouse and a keyboard. For example, the input interface 21 also includes an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the device and outputs the electrical signal to the control circuit.

The display 22 displays various information and various images. Specifically, the display 22 converts various information and image data sent from the system control circuit 27 into electrical signals for display and outputs the electrical signals. For example, the display 22 is realized by a liquid crystal monitor, a CRT (Cathode Ray Tube) monitor, a touch panel, or the like.

The bed control circuit 23 is a processing circuit that controls the bed driver 13 . Specifically, the bed control circuit 23 controls the bed driver 13 according to instructions received from the operator through the input interface 21 .

The data storage circuit 24 stores various data used in the PET device 100 . For example, the data storage circuit 24 is implemented by a semiconductor memory device such as a RAM (Random Access Memory) or flash memory, a hard disk, an optical disk, or the like.

The coincidence information generation circuit 25 is a processing circuit that uses the count information collected by the count information collection circuit 15 to generate a time-series list of coincidence count information. Specifically, the coincidence counting information generation circuit 25 retrieves a set of counting information in which pair annihilation gamma rays are counted substantially simultaneously from the counting information list stored in the data storage circuit 24 based on the detection time of the counting information. do. Then, the coincidence counting information generation circuit 25 generates coincidence counting information for each set of count information retrieved, and stores the generated coincidence counting information in the data storage circuit 24 while arranging them in roughly chronological order.

For example, the coincidence information generation circuit 25 generates coincidence information based on the coincidence information generation conditions received from the operator through the input interface 21 . As an example, for example, the coincidence counting information generation circuit 25 generates coincidence counting information based on the time window width. In this case, the coincidence counting information generating circuit 25 refers to the data storage circuit 24 and searches for a set of counting information whose detection time difference is within the time window width between the detector modules 140 . For example, the coincidence counting information generation circuit 25 creates a set that satisfies the coincidence counting information generation condition: "detection element number: P11, energy value: E11, detection time: T11" and "detection element number: P22, energy value: E22, Detection time: T22" is retrieved, this set is generated as coincidence counting information and stored in the coincidence counting information storage circuit 24b. Note that the coincidence counting information generation circuit 25 may generate the coincidence counting information using the energy window width as well as the time window width.

The image reconstruction circuit 26 is a processing circuit that reconstructs a PET image. Specifically, the image reconstruction circuit 26 reads the time-series list of the coincidence counting information stored in the coincidence counting information storage circuit 24b, and reconstructs the PET image using the read time-series list. The image reconstruction circuit 26 also stores the reconstructed PET image in the PET image storage circuit 24c.

The system control circuit 27 is a processing circuit that performs overall control of the PET apparatus 100 by controlling each part of the gantry 10 and the console 20 . For example, the system control circuit 27 controls imaging of the subject P by the PET apparatus 100 by controlling the bed control circuit 23 , the coincidence information generation circuit 25 , and the image reconstruction circuit 26 .

Here, among the components described above, for example, the count information collection circuit 15, the bed control circuit 23, the coincidence counting information generation circuit 25, the image reconstruction circuit 26, and the system control circuit 27 are each implemented by a processor. In this case, the processing functions of each processing circuit are stored in the data storage circuit 24 in the form of a computer-executable program, for example. Each processing circuit reads out each program from the data storage circuit 24 and executes it, thereby realizing a function corresponding to each program. Here, each processing circuit may be composed of a plurality of processors, and each processor may implement each processing function by executing a program. Also, the processing functions of each processing circuit may be appropriately distributed or integrated in a single or a plurality of processing circuits. Also, although the single data storage circuit 24 stores the programs corresponding to the respective processing functions here, a plurality of storage circuits may be arranged in a distributed manner so that the processing circuits correspond to individual storage circuits. A configuration for reading out a program that

The configuration example of the PET apparatus 100 according to the first embodiment has been described above. Here, as described above, in the PET apparatus 100 according to this embodiment, the PET detector 14 is formed in a cylindrical shape. Therefore, in the PET apparatus 100 according to the present embodiment, the detection range of pair annihilation gamma rays, that is, the FOV (Field Of View) is longer in the central axis direction than in a ring-shaped PET detector.

As described above, when the FOV is long in the central axis direction, the thickness of the LOR obtained by each pair of detection elements 141 included in the plurality of detection elements 141 of the PET detector 14 increases. Here, LOR is a line connecting two detection elements 141 and is defined as having a thickness corresponding to the cross-sectional size of each detection element 141 .

FIG. 3 is a diagram showing a comparative example of the PET device 100 according to this embodiment.

Here, FIG. 3 conceptually shows a cross section along the central axis A of the cylindrically formed PET detector. For example, as shown in FIG. 3, in a cylindrical PET detector, it is assumed that detection elements 141x of the same size are arranged side by side in the central axis direction. In this case, the thickness of the LOR 30 obtained by the pair of detecting elements 141x located diagonally between the end regions in the central axis direction of the PET detector is the thickness of the central region in the central axis direction of the PET detector. It is large compared to the thickness of the LOR obtained by the pair of arranged detector elements 141x.

As described above, when the thickness of the LOR becomes large, the accuracy of specifying the generation position of pair annihilation gamma rays decreases, and the spatial resolution of the PET apparatus 100 deteriorates. As a technique for preventing such degradation of spatial resolution, for example, DOI (Depth Of Interaction) technique is known. The DOI technology is a technology that can obtain information in the depth direction of the detection element, and by limiting the LOR region based on the depth information, it improves the accuracy of identifying the position of the annihilation gamma ray. be able to.

However, since the DOI technique obtains different signals depending on the position of the detection element in the depth direction, it is difficult to obtain such signals, and there is concern that the introduction cost is high. Furthermore, when the DOI technique is used, the circuit scale of the A/D converter in the subsequent stage increases, so there is concern that the cost will increase in this respect as well. Therefore, it is considered difficult to apply the DOI technique to all the detection elements 141 of the PET detector 14 .

For this reason, the PET apparatus 100 according to this embodiment is configured to improve the spatial resolution even when the PET detector 14 has an axially long FOV.

Furthermore, the PET apparatus 100 according to this embodiment is configured to improve spatial resolution while suppressing an increase in cost, compared to the case where DOI technology is applied to all the detection elements 141 .

Specifically, in the present embodiment, the PET detector 14 has the plurality of detection elements 141 arranged in the central region of the PET detector 14 in the central axis direction. Each detector element 141 is arranged such that when translated to each of the end regions, an LOR having a thickness smaller than that obtained by a pair of detector elements 141 located diagonally between the end regions is obtained. are placed.

For example, in the PET detector 14, when the detection element 141 arranged in the central region in the central axis direction is translated to both end regions in the central axis direction, similar to the comparative example shown in FIG. The thickness of the LOR obtained by the pair of detector elements 141 located diagonally between the end regions is larger than the thickness of the LOR obtained by the pair of detector elements 141 arranged in the central region. .

On the other hand, in the present embodiment, the thickness of the LOR obtained when each detecting element 141 included in the PET detector 14 is translated to each of both end regions in the central axis direction of the PET detector 14 is obtained. are arranged so as to obtain an LOR with a thickness smaller than that of the .

Here, for example, the thickness of the LOR obtained by a pair of detection elements 141 is defined according to the cross-sectional size of each detection element 141 along the circumferential direction and radial direction of the PET detector 14 .

FIG. 4 is a diagram showing an example of LOR obtained by a pair of detection elements 141 included in the PET detector 14 according to this embodiment.

For example, as shown in FIG. 4, the thickness L _LOR of the LOR 30 obtained by the two detection elements 141 included in the PET detector 14 is determined by the circumferential direction of the PET detector 14 in each detection element 141 (arrow D _C direction) and radial direction (direction of arrow D _R ) and the distance between line segments connecting two vertices located diagonally among four vertices of the cross section X along the radial direction (direction of arrow D R ).

For example, if the angle between the line connecting the centers of the cross sections X of the detection elements 141 and the center axis A of the PET detector 14 is θ, the thickness L _LOR of the LOR 30 is expressed by the following formula.

L _LOR = l cos θ + d sin θ

Here, as described above, when the detection element 141 arranged in the central region in the central axis direction of the PET detector 14 is translated to both end regions in the central axis direction, the angle θ becomes smaller, Along with this, the thickness L _LOR of the LOR 30 increases.

In such a case, in the present embodiment, each detecting element 141 included in the PET detector 14 is moved from an angle θ to each of both end regions in the central axis direction of the PET detector 14 in parallel. It is arranged to give a LOR 30 of small thickness compared to the resulting L _LOR .

More specifically, in the present embodiment, the PET detector 14 is arranged at both end regions in the central axis direction of the PET detector 14 among the plurality of detection elements 141. is configured to be identified by DOI technology.

For example, in the PET detector 14, the detection elements 141 arranged in both end regions in the central axis direction of the PET detector 14 are DOI detection elements divided in the radial direction of the PET detector 14. , the DOI detection element is configured to identify the light emitting position in the detection element 141 .

FIG. 5 is a diagram showing a configuration example of the PET detector 14 according to the first embodiment.

Here, FIG. 5 conceptually shows a cross section along the central axis A of the PET detector 14. As shown in FIG. For example, as shown in FIG. 5, in the present embodiment, the PET detector 14 is configured so that the number of divisions of the detection elements in the radial direction increases as it approaches both end regions in the central axis direction of the PET detector 14. It is

For example, in the example shown in FIG. 5, in the PET detector 14, a detection element 141a that is not a DOI detection element, i.e., that is not divided, is arranged in the central region of the PET detector 14 in the central axis direction. there is DOI detection elements 141b, which are divided into four detection elements, are arranged in both end regions of the PET detector 14 in the central axis direction. Between the central region and the both end regions of the PET detector 14, a DOI detection element divided into two, which has a smaller number of divisions than the DOI detection elements 141b arranged in the both end regions, is provided. 141c is arranged.

In this case, for the DOI detection elements 141b and 141c, the PET detector 14 identifies the light emission position for each of the divided detection elements, and the PET detector 14 detects the area of the LOR 30 obtained by each DOI detection element. It can be limited radially.

Here, an example in which the PET detector 14 is configured so that the number of divisions of the detection elements increases as it approaches both end regions in the central axis direction of the PET detector 14 has been described, but the embodiment is limited to this. can't That is, in the present embodiment, at least the detection elements 141 arranged in both end regions in the central axis direction should be DOI detection elements. For example, the detection elements 141 arranged between the center region and the end regions in the central axis direction of the PET detector 14 may be DOI detection elements or undivided detection elements. good. Further, for example, when the detection element 141 arranged between the central region and the end regions in the central axis direction of the PET detector 14 is a DOI detection element, the DOI detection elements arranged in the end regions The number of divisions may be the same.

Also, here, an example in which a DOI detection element in which the detection element is divided in the radial direction of the PET detector 14 is used has been described. , but not limited to this.

For example, the PET detector 14 has an optical sensor provided on at least one surface of the detection element 141 arranged in both end regions in the central axis direction of the PET detector 14, and the optical sensor detects the detection element. It may be configured to identify the light emitting position within 141 .

FIG. 6 is a diagram showing another configuration example of the PET detector 14 according to the first embodiment.

For example, as shown in FIG. 6, among the plurality of surfaces of the detection elements 141d arranged in the both end regions of the PET detector 14 in the central axis direction, optical sensors are provided on both end faces in the radial direction of the PET detector 14, respectively. 144 are provided.

The optical sensor 144 detects the scintillation photons output from the detection element 141d, converts them into electrical signals, and outputs the electrical signals. For example, the optical sensor 144 is a SiPM (Silicon Photomultiplier) such as an MPPC (Multi-Pixel Photon Counter).

In this case, the PET detector 14 identifies the number of scintillation photons detected by each photosensor 144 based on the electrical signals output from each photosensor 144 . Then, the PET detector 14 specifies the light emission position according to the ratio of the number of scintillation photons detected by the two optical sensors 144, and the area of the LOR 30 obtained by the detection element 141d is defined by the radius of the PET detector 14. direction can be limited.

The number of surfaces of the detection element 141d on which the optical sensors 144 are provided is not limited to two, and may be provided on all six surfaces of the detection element 141d, or may be provided on three, four, or five surfaces. good. Also, the optical sensors 144 do not necessarily need to be provided on both radial end faces, and for example, a plurality of optical sensors 144 may be provided on one of a plurality of radial side faces. In this case, among the optical sensors 144 arranged in the radial direction, the output of the optical sensor 144 closest to the light emission position is increased, thereby making it possible to identify the light emission position in the radial direction.

As described above, in the first embodiment, by specifying the light emitting positions in the detection elements 141 arranged in both end regions in the central axis direction of the PET detector 14 by the DOI technique, The thickness of the LOR 30 obtained by the pair of detecting elements 141 diagonally positioned between the end regions can be reduced compared to the case where the detecting elements 141 are moved parallel to each of the end regions. Therefore, according to the first embodiment, the spatial resolution can be improved even when the PET detector 14 has a long FOV in the axial direction.

Further, in the first embodiment, instead of applying the DOI technique to all the detection elements 141 of the PET detector 14, the detection elements 141 arranged in both end regions in the central axis direction of the PET detector 14 are , the DOI technology is applied. Therefore, according to the first embodiment, it is possible to improve the spatial resolution while suppressing an increase in cost, compared to the case where the DOI technology is applied to all the detection elements 141 .

In the above-described first embodiment, an example in which the DOI technique is applied to the detection elements 141 arranged in both end regions in the central axis direction of the PET detector 14 has been described. Not limited. Therefore, other embodiments of the PET detector 14 will be described below. In addition, in the embodiment described below, the points different from the first embodiment will be mainly described, and the description of the contents common to the first embodiment will be omitted.

(Second embodiment)
For example, in the PET detector 14, among the plurality of detecting elements 141, the thickness in the radial direction of the PET detector 14 of the detecting elements 141 arranged in both end regions in the central axis direction of the PET detector 14 is equal to the central axis It may be configured to be smaller than the thickness in the radial direction of the detection element 141 arranged in the central region in the direction.

FIG. 7 is a diagram showing a configuration example of the PET detector 14 according to the second embodiment.

Here, FIG. 7 conceptually shows a cross section along the central axis A of the PET detector 14. As shown in FIG. For example, as shown in FIG. 7, in the present embodiment, in the PET detector 14, the thickness in the radial direction of the PET detector 14 is Each detection element 141 is arranged so that .

For example, in the example shown in FIG. 7, in the PET detector 14, both end regions in the central axis direction of the PET detector 14 have detecting elements having a smaller thickness in the radial direction than the detecting element 141e arranged in the central region. 141f are arranged. In addition, between the center region and both end regions in the central axis direction of the PET detector 14, the thickness in the radial direction is smaller than the detection element 141e arranged in the center region, and the thickness is arranged in both end regions. A detecting element 141g having a thickness in the radial direction smaller than that of the detecting element 141f is arranged.

Here, an example in which each detecting element 141 is arranged so that the thickness becomes smaller as it approaches the both end regions from the center region in the central axis direction of the PET detector 14 has been described, but the embodiment is this. is not limited to That is, in the present embodiment, at least the detecting elements 141f arranged in both end regions in the central axis direction should have a smaller thickness than the detecting elements 141e arranged in the central region. For example, the detection element 141g arranged between the central region and the end regions in the central axis direction of the PET detector 14 may have the same thickness as the detection element 141e arranged in the central region, The thickness may be the same as that of the detection elements 141f arranged in the both end regions.

Thus, in the second embodiment, by making the thickness in the radial direction of the detection elements 141f arranged in both end regions in the central axis direction of the PET detector 14 smaller than the thickness in the radial direction of the detection elements 141e arranged in the central region, The thickness of the LOR 30 obtained by the pair of detecting elements 141f located diagonally between the end regions is reduced compared to the case where the detecting element 141e arranged in the center region is translated to each of the end regions. be able to. Therefore, according to the second embodiment, the spatial resolution can be improved even when the PET detector 14 has a long FOV in the axial direction.

(Third Embodiment)
Further, for example, in the PET detector 14 , among the plurality of detection elements 141 , the detection elements 141 arranged in the both end regions in the central axis direction of the PET detector 14 are arranged on the center side of the PET detector 14 on the incident surface. may be arranged so as to face the

FIG. 8 is a diagram showing a configuration example of the PET detector 14 according to the third embodiment.

Here, FIG. 8 conceptually shows a cross section along the central axis A of the PET detector 14 . For example, as shown in FIG. 8, in the present embodiment, in the PET detector 14, all the detection elements 141h are arranged with the incident surface directed toward the center.

For example, in the example shown in FIG. 8, in the PET detector 14, each detection element 141h is arranged along the spherical surface S of a sphere centered at the center of the PET detector 14, with the incident surface on the center side of the PET detector 14. placed to face. In other words, each detection element 141 has an incident surface on the center side of the PET detector 14 along the circumference of a circle centered on the center of the PET detector 14 within a plane passing through the center of the PET detector 14 . placed to face. Since the vicinity of the intersection of the central axis of the PET detector 14 and the spherical surface S is the position where the imaging aperture is formed, the detection element 141h is not arranged.

Here, an example in which all the detection elements 141h are arranged with the incident surfaces facing the center side has been described, but the embodiment is not limited to this. That is, in the present embodiment, at least the detection elements 141 arranged in the both end regions in the central axis direction should be arranged with the incident surfaces directed toward the center. For example, the detection elements 141h arranged in both end regions in the central axis direction are arranged with the incident surface facing the center side of the PET detector 14, and the other detection elements 141h are arranged at the center of the PET detector 14. It may be arranged with the incident surface facing the axis.

As described above, in the third embodiment, the detection elements 141h arranged in both end regions in the central axis direction of the PET detector 14 are arranged so that the incident surfaces of the detection elements 141h face the center side of the PET detector 14. , compared to the case where the detector elements 141h arranged in the center region are translated to each of the end regions, the pair of detector elements 141h located diagonally between the end regions obtains The thickness of the LOR 30 that is used can be reduced. Therefore, according to the third embodiment, spatial resolution can be improved even when the PET detector 14 has a long FOV in the axial direction.

In the third embodiment, in the PET detector 14, the LOR 31 obtained by the pair of detection elements 141h arranged in the same plane perpendicular to the central axis direction becomes thicker as it approaches both end regions in the central axis direction. becomes larger. However, since the sensitivity of the PET detector 14 is maximized near the center and decreases near the edges, it is considered that such a configuration does not significantly affect the spatial resolution.

Although the first to third embodiments have been described above, devices to which the PET detectors described in each embodiment can be applied are not limited to PET devices. For example, the PET detector described in each of the above-described embodiments may be a PET-CT device that combines a PET device and an X-ray CT (Computed Tomography) device, or a PET-MRI (Magnetic MRI) device that combines a PET device and an MRI device. Resonance Imaging) can be similarly applied as a PET detector provided in an apparatus.

In addition, the term "processor" used in the above description is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or an application specific integrated circuit (ASIC), a programmable logic device (eg, Simple Programmable Logic Device (SPLD), Complex Programmable Logic Device (CPLD), and Field Programmable Gate Array (FPGA)). Instead of storing the program in the memory circuit, the program may be directly incorporated in the circuit of the processor. In this case, the processor implements its functions by reading and executing the program embedded in the circuit. Further, each processor of the present embodiment is not limited to being configured as a single circuit for each processor, and may be configured as one processor by combining a plurality of independent circuits to realize its function. good. Furthermore, a plurality of components in FIG. 1 may be integrated into one processor to realize its functions.

Here, the program to be executed by the processor is provided by being pre-installed in, for example, a ROM (Read Only Memory), a storage circuit, or the like. This program is a file in a format that can be installed in these devices or a file in a format that can be installed on a computer such as CD (Compact Disk)-ROM, FD (Flexible Disk), CD-R (Recordable), DVD (Digital Versatile Disk), etc. may be recorded on a readable storage medium and provided. Also, this program may be provided or distributed by being stored on a computer connected to a network such as the Internet and downloaded via the network. For example, this program is composed of modules including each functional unit described above. As actual hardware, the CPU reads out a program from a storage medium such as a ROM and executes it, so that each module is loaded onto the main storage device and generated on the main storage device.

According to at least one embodiment described above, it is possible to improve the spatial resolution of the PET apparatus.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

100 Positron Emission Tomography (PET) Device 14 PET Detector 140 Detector Module 141 Detection Element

Claims (5)

A PET detector in which a plurality of detection elements are arranged in the circumferential direction and the central axis direction,
Each of the plurality of detection elements has an axial direction along a cross section of the detection element along the central axis of the PET detector in a radial direction of the PET detector perpendicular to the central axis direction of the PET detector. are arranged along the
In the PET detector, among the plurality of detection elements, the detection elements arranged in both end regions in the central axis direction are compared with the detection elements arranged in the central region in the central axis direction. By using the detection element capable of limiting the detection range in the radial direction of the PET detector, the detection element arranged in the central region in the central axis direction is parallel to each of the end regions in the central axis direction. It is configured such that when it is moved, an LOR having a smaller thickness than the thickness of the LOR (Line Of Response) obtained by a pair of detection elements located diagonally between the end regions is obtained.
Positron emission tomography system. The PET detector uses a detection element capable of specifying a light emission position in the detection element by DOI (Depth Of Interaction) technology as the detection element arranged in the both end regions. configured to obtain a small thickness LOR,
The positron emission tomography apparatus according to claim 1. The PET detector uses DOI detection elements, which are divided in the radial direction of the PET detector, as the detection elements arranged in the both end regions. configured to identify the position of light emission at
The positron emission tomography apparatus according to claim 2. The PET detector has an optical sensor provided on at least one surface of the detection elements arranged in the end regions, and is configured to identify the light emission position in the detection element by the optical sensor. has been
The positron emission tomography apparatus according to claim 2. In the PET detector, the thickness in the radial direction of the detecting element arranged in the both end regions is equal to the thickness in the radial direction of the detecting element arranged in the central region in the central axis direction By using a detection element smaller than the thickness, it is configured so that the LOR with the small thickness can be obtained.
The positron emission tomography apparatus according to claim 1.

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