JP4621188B2 - Nuclear medicine diagnostic equipment - Google Patents

Description

  The present invention relates to a nuclear medicine diagnostic apparatus, and more particularly to a positron emission computed tomography apparatus (hereinafter referred to as a PET apparatus) which is a kind of nuclear medicine diagnostic apparatus using a radiation detector.

A PET test is a radiopharmaceutical for PET (hereinafter referred to as “PET”) that contains positron emitting nuclides (eg, ¹¹ C, ¹³ N, ¹⁵ O, ¹⁸ F, etc.) and is given the property of being metabolized in the affected area (lesion) to be examined. , PET drug) is administered to the subject, and after a predetermined time, the PET drug is accumulated in the affected part where the PET drug is accumulated (in which part is consumed). It is specified by detecting γ rays released due to the drug. The positrons emitted from the PET drug are combined with nearby electrons and annihilated, and a pair of γ rays are emitted. These pairs of γ rays (hereinafter referred to as γ ray pairs) are emitted in directions almost opposite to each other. Therefore, based on the detection signal of the γ rays, the source position (affected part position) of the γ rays is determined. A straight line can be specified.

  In the PET examination, a large number of gamma ray pairs released from the body due to the PET drug accumulated in the affected area are detected in this way, and the subject including the portion (affected area position) where a lot of PET drug is consumed based on the data. A tomographic image of the specimen (hereinafter referred to as a PET image) is created. As a PET inspection apparatus for performing such a PET inspection, for example, a number of apparatuses such as the nuclear medicine diagnosis apparatus described in Patent Document 1 have already been proposed.

  Usually, a PET apparatus includes a plurality of radiation detectors that detect γ-rays, and determines which radiation detector has detected γ-rays and creates a PET image including the affected area. A doctor looks at the PET image and specifies the position of the affected part. Although γ rays may be transmitted as they are even if they are incident on the radiation detector, they are incident on the radiation detector and attenuated except in this case. The radiation detector having attenuated γ rays outputs a detection signal (charge) corresponding to the attenuation energy of the γ rays. In addition, the detected (attenuated) γ-rays are scattered in the radiation detector except for the case where the γ-rays are all attenuated. Scattered γ-rays (hereinafter referred to as scattered γ-rays) change the traveling direction and enter other radiation detectors at different incident angles. Of course, the scattered γ-ray may be transmitted through each incident radiation detector without being attenuated thereafter, or may be detected by being attenuated or scattered again by another radiation detector. That is, the γ-rays detected by the radiation detector include γ-rays before being scattered (which are not scattered by the radiation detector) (hereinafter referred to as non-scattered γ-rays) and scattered γ-rays. It will be. In addition, gamma rays may be scattered in the patient's body (hereinafter referred to as internally scattered gamma rays), changing the traveling direction, and reaching the radiation detector in a state where energy is attenuated.

  Here, as described above, since the internally scattered γ-ray has a different traveling direction from the time of generation, the source of the γ-ray does not exist on the extension of the vector of the internally scattered γ-ray. That is, the PET image data based on the detection signal of the internally scattered γ-ray becomes incorrect information and causes noise. Therefore, conventionally, taking into account that the internally scattered γ-rays attenuate energy during scattering, it has been common to determine and remove γ-rays having energy below a set energy threshold as in-body scattered γ-rays. However, in this case, even if the γ-rays are not scattered in the patient's body, the energy of the scattered γ-rays does not exceed the energy threshold value, so that the PET image data collection efficiency may be reduced.

  On the other hand, in the nuclear medicine diagnosis apparatus described in Patent Document 1, when a plurality of γ rays are detected, the detection signals of these γ rays are simultaneously counted, and the sources of the γ rays detected almost simultaneously are detected. It is considered that they are the same, and it is determined whether or not the calculated total energy is a value within the set range and whether or not non-scattered γ-rays are included therein. Then, if it is determined that it contains non-scattered γ-rays, the initial incident position of γ-rays is selected by selecting one of the detected γ-rays that has a statistically high probability of being non-scattered γ-rays is doing.

However, since a PET apparatus that generates a 3D PET image does not use a collimator, the input rate of γ rays to the semiconductor radiation detector is high, and it is necessary to determine scattered γ rays at a higher speed. Further, in this prior art, in order to shorten the imaging time with respect to 511 keV high-energy γ-rays that are likely to be scattered, the detection of a plurality of scattered γ-rays by one incident γ-ray is specified, and a PET image It does not solve the problem of high-speed processing when used to generate
In particular, the detection energy at the time of scattering of γ rays is small, and the rise in the waveform of the γ ray detection signal in that case is delayed. Using the leading edge trigger method, which is one of the methods for measuring the detection time from the γ-ray detection signal, the detection signal (event) with low energy overlaps with the next γ-ray detection signal (event) at the detection timing. End up. For example, even if a circuit in which an error in detection time due to energy is less likely to occur is used, the time resolution of the detection time is degraded at low energy.
In addition, when a compound semiconductor is used for a γ-ray detector, the time resolution of the detection time deteriorates due to the waveform fluctuation of the γ-ray detection signal due to the difference in mobility of electrons and holes, resulting in scattering by one incident γ-ray. It becomes necessary to widen the time window for determining that the signals are a plurality of γ-ray detection signals. As a result, the number of events that are candidates for scattered radiation processing increases, and a technique for efficiently performing scattered radiation processing is required.

An object of the present invention is to provide a nuclear medicine diagnostic apparatus capable of efficiently identifying scattered γ-rays for a plurality of γ-ray detection signals by the same γ-ray and creating a highly accurate PET image. is there.
JP 2000-321357 A

  In order to achieve the above-described object, the present invention provides a scattered radiation processing unit that serves as a reference for each of detected γ-ray information serving as a reference and other detected γ-ray information among a plurality of detected γ-ray information. Based on the detector ID included in the detected γ-ray information, a first scattered radiation determination as to whether or not the detected γ-ray information is caused by the same γ-ray included in the preset first spatial range. A plurality of the detected γ-ray information based on the first scattered radiation determination, and the first scattered radiation information based on other than the detected γ-ray information determined to be caused by the same γ-ray in the first scattered radiation determination. A second scattered ray determination is performed to determine whether or not the detected γ-ray information is derived from the same γ-ray from the γ-ray detector included in the second spatial range that is set in advance wider than the spatial range, and the second Based on the scattered radiation determination of the To.

  According to the present invention, it is possible to provide a nuclear medicine diagnostic apparatus that can efficiently identify scattered γ-rays for a plurality of γ-ray detection signals based on the same γ-ray and create a highly accurate PET image. it can.

<< First Embodiment >>
Next, a nuclear medicine diagnosis apparatus which is a preferred embodiment of the present invention will be described with reference to the drawings as appropriate.
In the following, description of elements applied to the present embodiment, such as arrangement (layout) of each element on the substrate such as the nuclear medicine diagnosis apparatus of this embodiment, analog ASIC, etc., and unitization of the substrate, method of scattered radiation processing Will be explained.
The analog ASIC means an application specific integrated circuit (ASIC) that is an application specific IC that processes an analog signal, and is a kind of LSI (Large Scale Integrated Circuit).

(Nuclear medicine diagnostic equipment)
First, the nuclear medicine diagnostic apparatus of this embodiment will be described.
As shown in FIG. 1, a PET apparatus 1 as a nuclear medicine diagnostic apparatus includes a camera 11, a data processing apparatus 12, an operation console 13, and the like. The subject P (see FIG. 2) is placed on the bed 14 and photographed by the camera 11.
The operation console 13 includes a display device 13a that displays a tomographic image of the PET apparatus 1, a state check result of the PET apparatus 1, and the like, and an input operation unit 13b such as a keyboard and a mouse.

As shown in FIG. 2, a semiconductor radiation detector (γ-ray detector, hereinafter simply referred to as a detector) 21 is provided inside the camera 11 in order to detect γ-rays emitted from the subject P (FIG. 4). , See FIG. 5), and a plurality of detector units 2 containing a plurality of combined substrates (unit substrates) 20 (see FIG. 6 for details) are arranged in the circumferential direction and released from the body of the subject P. The detected γ rays are detected by the detector 21.
The detector unit 2 has an integrated circuit (ASIC) for measuring the detection energy and detection time of γ-rays on the coupling substrate 20 and measures the detection energy and detection time of the detected γ-rays. The address of the detector 21 that has detected the γ-ray is detected, and these are output to the data processing device 12 as detected γ-ray information.

The detector unit 2 includes detected energy data (detected energy value information) of detected γ rays, detected time data (detected time information), and a detector ID (detector address information) corresponding to the address of the detector 21 described above. ) Including packet data (detected γ-ray information) is output to the data processing device 12 via the data collection unit 3 (3A, 3B, 3C, 3D). The data collection unit 3 transfers part of the packet data from the detector unit 2 to the adjacent data collection unit 3.
Although the details will be described later, the data collection unit 3 arranges packet data output from the plurality of detector units 2 in order based on the detection time information, and scattered ray processing described later between the detector units 2. It has a function.

  As shown in FIG. 2, the data processing device 12 includes a storage device (not shown), a simultaneous measurement device 12A, and a tomographic image information creation device 12B. The data processing device 12 captures packet data. The simultaneous measurement device 12A performs simultaneous measurement determination based on the packet data, in particular, the detection time data and the detector ID. Then, the detection position of the 511 keV γ-ray is specified and stored in the storage device. The tomogram information creation device 12B creates a functional image based on the specified position and displays it on the display device 13a.

Incidentally, the subject P is administered with a radiopharmaceutical, for example, fluorodioxyglucose (FDG) containing ¹⁸ F of a half-life of 110/110, and from the body of the subject P, the positron released from the FDG At the time of annihilation, a pair of 511 keV gamma rays (annihilation gamma rays) is emitted in a direction of approximately 180 ° with respect to each other.
At this time, each detector 21 of the camera 11 surrounds the bed 14. From the detector unit 2 to the data processing device 12 via the data collection unit 3, the detected energy value information and the detection time information obtained based on the γ-ray detection signal when the detector 21 interacts with the γ-ray. , And the detector ID are output for each detector 21 included in the detector unit 2.

  As shown in FIG. 3A, the detector unit 2 has a configuration in which 60 to 70 pieces are detachably disposed in the opening 11b of the camera 11 in the circumferential direction so that maintenance and inspection can be easily performed. ing. The detector unit 2 is mounted via a unit support member 2A. Further, as shown in FIG. 3B, the detector unit 2 is mounted on the camera 11 with one end supported by the unit support member 2A. The unit support member 2A has a hollow disk shape (doughnut shape), and includes a large number of openings 11b in which the detector unit 2 is mounted in the circumferential direction of the camera 11 (the number of detector units 2 to be mounted). Yes. Thus, in order to support the detector unit 2 at one end, a flange portion serving as a stopper is provided on the front side of the housing 30 of the detector unit 2 in the body axis direction.

  Incidentally, when trying to arrange the detector units 2 as closely as possible in the circumferential direction, the flange portion on the inner side in the circumferential direction becomes an obstacle. In view of this, the flange portion, which is a hindrance, may be eliminated from the housing 30 to leave the outer circumferential flange portion. Another unit support member 2A may be installed in the body axis direction, and both ends of the detector unit 2 may be held by both unit support members 2A.

When the detector unit 2 is attached to the camera 11, the lid 11a is removed to expose the unit support member 2A, and the detector unit 2 is inserted and attached from the opening 11b until the flange portion abuts. ing. By inserting and mounting, the respective connectors of the power supply and signal wiring (not shown) of the camera 11 and the corresponding connectors of the detector unit 2 are connected, and the connection of the signal and power supply between the camera 11 and the detector unit 2 is performed. Is made.
The configurations of the detector 21, the coupling substrate 20, and the detector unit 2 will be described in detail later.
Hereinafter, the characteristic part of this embodiment will be described.

(Semiconductor radiation detector)
First, the detector 21 applied to this embodiment is demonstrated, referring FIG. 4, FIG. 4 is a diagram conceptually showing the laminated structure of the detector 21, and FIG. 5A is a perspective view schematically showing detection elements and electrodes which are components of the detector. FIG. 5B is a perspective view after the layers are laminated and integrated.
As shown in FIG. 4, the detector 21 has thin plate (film-like) electrodes (anode A, cathode C) on both sides of a semiconductor radiation detection element (hereinafter referred to as detection element) 211 made of a plate-like semiconductor material S. For example, a layered structure in which the layers covered with are stacked in five layers.
Among these, the semiconductor material S is any of the above-described CdTe (cadmium telluride), CdZnTe (zinc cadmium telluride), HgI ₂ (mercury iodide), TlBr (thallium bromide), GaAs (gallium arsenide), and the like. It is composed of a single crystal.
The electrode A (anode A) and the electrode C (cathode C) are made of any material such as Pt (platinum), Au (gold), and In (indium).
In the following description, it is assumed that the semiconductor material S is a slice of CdTe single crystal. The detected radiation is assumed to be 511 keV γ rays used in the PET apparatus 1.

The thickness of one layer of the semiconductor material S (detection element 211) shown in FIG. 4 is, for example, 0.5 to 1.5 mm. Each of the anode A and the cathode C has a thickness of about 20 μm.
In the detector 21 having the laminated structure shown in FIG. 4, the anodes A and the cathodes C are connected in common, so that each layer is not configured to detect radiation independently of the other layers. In other words, when the γ-ray and the semiconductor material S interact with each other, it is not determined whether it occurred in the uppermost layer or the lowermost layer. Of course, it can also be set as the structure detected for every layer.

Incidentally, the five-layer structure as described above is more convenient as a detector because the rising speed of the γ-ray detection signal and the crest value are higher when the thickness of the semiconductor material S is reduced. If the thickness is small, the amount of γ-rays that pass through without interacting with the semiconductor material S increases, so that the amount of γ-rays that pass through is reduced while improving the charge collection efficiency. This is to increase the interaction between γ rays and γ rays, that is, to increase the number of counts.
With the configuration of the detector 21 having such a laminated structure, a better rising of the γ-ray detection signal and a more accurate peak value can be obtained, and the count number of γ-rays that interact with the semiconductor material S can be obtained. It is possible to increase both, that is, increase sensitivity.

The area of the electrodes (anode A, cathode C) is preferably 4 to 120 mm ² . The increase in area increases the capacitance (stray capacitance) of the detector 21 and the noise increases due to the increase in stray capacitance. Therefore, it is preferable that the area of the electrode be as small as possible. Further, since the charge generated at the time of detecting γ-rays is partially stored in the stray capacitance, the amount of charge stored in the preamplifier 24a of the analog ASIC 24 (see FIG. 7) and the output voltage (wave) are increased when the stray capacitance increases. There is a problem that the (high value) decreases. When CdTe is used as the detector 21, the relative dielectric constant is 11, and when the area of the detector 21 is 120 mm ² and the thickness is 1 mm, the capacitance is 12 pF, and the stray capacitance such as a circuit connector is several pF. Given something, it can't be ignored. Accordingly, the area of the electrode is preferably 120 mm ² or less.
Further, the lower limit value of the electrode area is determined from the position resolution of the PET apparatus 1.

  In the above description, the semiconductor material S that interacts with γ-rays is CdTe. However, it goes without saying that the semiconductor material S may be CdZnTe, TlBr, GaAs, or the like.

(Coupling substrate; detector substrate and ASIC substrate)
Next, the detailed structure of the combined substrate (unit substrate) 20 installed in the detector unit 2 will be described with reference to FIG. FIG. 6A is a front view showing the coupling substrate, and FIG. 6B is a side view of FIG.
The coupling substrate 20 includes a detector substrate 20A having a plurality of detectors 21 on both sides, a capacitor 22, a resistor 23, an analog ASIC 24, and an analog / digital converter (hereinafter referred to as ADC) 25 on both sides. The ASIC board 20B on which the digital ASIC 26 is installed is connected by the connector C1.

(Detector board)
As shown in FIG. 6A, the detector substrate 20A is arranged on one side of the substrate body 20a in the horizontal row in FIG. 6A corresponding to the body axis direction of the subject P, for example, Sixteen detectors 21 are arranged, and four rows are arranged in the vertical direction in FIG. 6A corresponding to the radial direction with respect to the body axis of the subject P, that is, 16 horizontal × 4 vertical. A total of 64 detectors 21 are arranged in a grid pattern. Further, as shown in FIG. 6B, detectors 21 are similarly installed on the other surface of the detector substrate 20A, and a total of 128 detectors 21 are provided on one detector substrate 20A. Is arranged.
Here, as the number of detectors 21 increases, it becomes easier to detect γ-rays, and the positional accuracy at the time of γ-ray detection can be increased. Therefore, the detector 21 is placed on the detector substrate 20A as closely as possible. Arranged.

  Incidentally, in FIG. 6A, detection is performed when γ-rays emitted from the subject P on the bed 14 travel from the lower side to the upper side (the direction of the arrow 32, that is, the radial direction of the camera 11). It is preferable that the arrangement of detectors 21 in the left-right direction on the instrument substrate 20A be dense because the number of γ rays that pass through (the number of γ rays that pass through the gap between the detectors 21) can be reduced. Thereby, the detection efficiency of γ-rays is increased, and the spatial resolution in the body axis direction of the obtained image can be increased.

In the detector substrate 20A of the present embodiment, as shown in FIG. 6B, the detector 21 is installed on both sides of the substrate body 20a. It can be shared by mounting 20a on both sides. For this reason, the number of the substrate main bodies 20a can be halved, and the detectors 21 can be arranged more densely in the circumferential direction of the body axis of the subject P. In addition, as described above, the number of detector substrates 20A (coupled substrate 20) can be reduced by half.
In the above description, the 16 horizontal detectors 21 are configured to be arranged in the body axis direction of the subject in the camera 11, but are not limited thereto. For example, 16 horizontal detectors 21 may be arranged in the camera 11 in the circumferential direction with respect to the body axis of the subject P.
The detector 21 may be disposed with the surfaces of the electrodes A and C shown in FIG. 5B parallel to the surface of the substrate body 20a, and the surfaces of the electrodes A and C are disposed on the substrate body. You may arrange | position perpendicularly to the surface of 20a.

  Between the anode A and the cathode C of each detector 21, for example, a potential difference (voltage) of 500 V is applied by a high-voltage power supply 27 (see FIG. 8) for charge collection. This voltage is supplied from the ASIC board 20B side to the detector board 20A side via the connector C1 (see FIG. 6A). A γ-ray detection signal output when each detector 21 detects γ-rays is supplied to the ASIC board 20B side via the connector C1. For this reason, in the board body 20a of the detector board 20A, board wiring (for detector applied voltage, for signal exchange) (not shown) for connecting the connector C1 and each detector 21 is provided. This intra-substrate wiring has a multilayer structure. The detector board 20A has a connector C1 connected to the in-board wiring connected to each detector 21, and has a structure connected to a connector C1 of an ASIC board 20B described later.

(ASIC board)
Next, the ASIC substrate 20B on which the ASIC is mounted will be described with reference to FIG. As shown in FIG. 6A, the ASIC board 20B has two analog ASICs 24 installed on both sides of the board body 20b and one digital ASIC 26 installed on one side. That is, one ASIC board 20B has a total of four analog ASICs 24 and one digital ASIC 26.
In addition, the ASIC substrate 20B has 32 ADCs 25 in total, 16 on each side of the substrate body 20b. In addition, capacitors 22 and resistors 23 corresponding to the number of detectors 21 are provided on both surfaces of one substrate body 20b. Further, in order to electrically connect the capacitor 22, the resistor 23, the analog ASIC 24, the ADC 25, and the digital ASIC 26, the ASIC board 20B (board body 20b) has a board (not shown) similar to the detector board 20A described above. Internal wiring is provided. This intra-substrate wiring also has a laminated structure.

As for the arrangement of these circuit elements 22, 23, 24, 25, and 26 and the wiring in the board, the signal supplied from the detector board 20A is supplied in the order of the capacitor 22, the resistor 23, the analog ASIC 24, the ADC 25, and the digital ASIC 26. It has become so.
The ASIC board 20B is connected to an in-board wiring connected to each capacitor 22, and is electrically connected to the detector board 20A. The data processing apparatus 12 side (unit integrated FPGA side described later) Board connector C2 for electrical connection.

(Connection structure of detector board and ASIC board)
As shown in FIG. 6B, the detector substrate 20A and the ASIC substrate 20B are provided with overlapping portions in the vicinity of the end portions, and connect the connectors C1 existing in these overlapping portions to each other. . This connection is made detachable (separate and connectable) with a fastening screw or the like.
Such a connection is made when the coupling substrate 20 in which the detector substrate 20A and the ASIC substrate 20B are connected (coupled) is supported in one end (cantilevered) or both ends in the horizontal direction. Since a force that bends or bends the bonding substrate 20 downward acts on the central portion (connection portion) of the substrate, the connection portion is easily bent or bent when the connection portion is formed by abutting the end faces. This is because it is easy to increase the strength of the connecting portion.

As the connector C1, for example, a spiral contact (registered trademark) is used in order to improve electrical connection. A spiral contact (registered trademark) has a characteristic that a ball-shaped connection terminal contacts a spiral contactor over a wide area to achieve good electrical connection.
When the ball-shaped connection terminal is provided on the ASIC substrate 20B side, the spiral contact is provided on the detector substrate 20A side, and when the ball-shaped connection terminal is provided on the detector substrate 20A side, The spiral contact is provided on the ASIC substrate 20B side.
By using such an electrical connection structure between the detector board 20A and the ASIC board 20B, a signal can be transmitted from the detector board 20A to the ASIC board 20B with low loss. When the loss is reduced, for example, the energy resolution as the detector 21 is improved.

In the above configuration, one detector board 20A is connected to the ASIC board 20B, but the detector board may be divided into a plurality of parts. For example, the configuration may be such that eight detectors 21 in the horizontal direction and four detectors 21 in the vertical direction are mounted on one board, and two detector boards are connected to the ASIC board.
Further, the detector substrate 20A and the ASIC substrate 20B may be configured by a single substrate body.

Next, the configuration and function of each circuit element on the ASIC substrate will be described with reference to FIGS.
FIG. 7 is a block diagram of the detector unit showing the schematic configuration of each of the analog ASIC and the digital ASIC and the connection relationship between the analog ASIC and the digital ASIC.
(Analog ASIC)
FIG. 8 is a block diagram schematically showing the functional configuration of the analog ASIC.
As shown in FIG. 8, one analog ASIC 24 includes an analog having a charge-sensitive preamplifier (hereinafter referred to as a preamplifier) 24a, and a fast system 24A and a slow system 24B connected thereto. For example, 32 sets of signal processing circuits 33 are provided. One analog ASIC 24 is obtained by converting 32 sets of analog signal processing circuits 33 into an LSI.

  The analog signal processing circuit 33 is provided for each detector 21, and one analog signal processing circuit 33 is connected to one detector 21. Here, the first system 24A includes a timing pick-off circuit 24b that outputs a timing signal for specifying the detection time of the γ-ray based on the γ-ray detection signal output from the preamplifier 24a. The timing pick-off circuit 24b generates a timing signal using a technique such as CFD or leading edge trigger. The slow system 24B has a predetermined time constant for the purpose of obtaining the detected energy (crest value) of the γ-ray based on the γ-ray detection signal, and a waveform shaping circuit 24d that shapes the signal waveform into a Gaussian shape. A peak hold circuit 24e is further connected to the waveform shaping circuit 24d. For example, a CR-RC filter or the like is used for the waveform shaping circuit 24d.

  Incidentally, the slow system 24B is named “slow” because it takes a certain amount of processing time to obtain the peak value. The signal output from the detector 21 and passed through the capacitor 22 is amplified by the preamplifier 24a, output as a γ-ray detection signal, further amplified by the waveform shaping circuit 24d, and input to the peak hold circuit 24e. The peak hold circuit 24e holds the maximum value of the γ-ray detection signal whose waveform has been shaped as described later, that is, the peak value proportional to the detected energy value of the γ-ray.

The capacitor 22 and the resistor 23 can be provided inside the analog ASIC 24. However, in order to obtain an appropriate capacitor capacity and an appropriate resistance value, and to reduce the size of the analog ASIC 24, the present embodiment Then, the capacitor 22 and the resistor 23 are disposed outside the analog ASIC 24.
Incidentally, it is said that the capacitor 22 and the resistor 23 are provided outside, so that there is less variation in individual capacitor capacity and resistance value.

The output of the slow system 24B of the analog ASIC 24 is supplied to the ADC 25 (see FIG. 8). Further, the output of the first system 24A and the output of the ADC 25 of the analog ASIC 24 are supplied to the digital ASIC 26.
Here, each analog ASIC 24 and digital ASIC 26 are connected by 32 wires for transmitting 32-channel fast system 24A signals one by one (see FIG. 7). The analog ASIC 24 and each ADC 25, and between each ADC 25 and the digital ASIC 26 are respectively connected by one wiring that collectively transmits the signals of the slow system 24B for the eight channels of the detector 21. (See FIG. 7).
Furthermore, from the digital ASIC 26, one ADC control signal line for controlling one associated ADC 25 corresponding to the analog signal processing circuit 33 for eight channels, and one analog signal processing circuit for each analog ASIC 24. A peak hold control signal line for 8 channels for individually controlling the 33 peak hold circuits 24 e is connected to the ADC 25 and the analog signal processing circuit 33.
The above-described peak hold control signal lines may be wired from the digital ASIC 26 to the analog signal processing circuits 33 one by one without consolidating the eight channels into one.

(Digital ASIC)
Next, the digital ASIC 26 will be described with reference to FIG.
As shown in FIG. 7, the digital ASIC 26 includes 16 sets of detection signal processing units 34 including eight timing detection units 35 and one detector control unit 36, and one data transfer unit 37. These are LSIs.

All the digital ASICs 26 provided in the PET apparatus 1 operate in synchronization with receiving a clock signal from a clock generation circuit (crystal oscillator) (not shown), for example, 500 MHz. The clock signal input to each digital ASIC 26 is input to each timing detection unit 35 in all detection signal processing units 34.
The timing detector 35 is provided for each detector 21 and receives a timing signal from the timing pick-off circuit 24b of the corresponding analog signal processing circuit 33. The timing detector 35 determines the detection time of the γ-ray based on the clock signal when the timing signal is input. Since the timing signal is based on the signal of the first system 24A of the analog ASIC 24, a time close to the true detection time can be set as the detection time (detection time information).

The detector control unit 36 has an address calculation function, an ADC / peak hold control function, a data correction function, and a packet data generation function.
(Address calculation function)
The address calculation function receives detection time information corresponding to the timing signal from which the γ-ray is detected from the timing detection unit 35, and identifies the detector ID. That is, the detector control unit 36 stores a detector ID for each timing detection unit 35 to be connected. When detection time information is input from a certain timing detection unit 35, the detector control unit 36 corresponds to the timing detection unit 35. The address calculation function is performed by specifying the detector ID. This is possible because the timing detector 35 is provided for each detector 21 and is connected to the detector controller 36.

(ADC / peak hold control function)
Furthermore, after the time information is input, the detector control unit 36 outputs a peak hold control signal to the analog signal processing circuit 33 for eight channels including the specified detector ID, and the detector ID and The ADC control signal is output to the ADC 25.

  Upon receiving the peak hold control signal, the peak hold circuit 24e of the analog signal processing circuit 33 performs peak hold processing on the signal input from the waveform shaping circuit 24d. Then, after a predetermined time, the reset signal is received from the detector control unit 36, and the peak hold process is canceled. The ADC 25 converts a peak value (voltage value) output from the peak hold circuit 24e of the analog signal processing circuit 33 corresponding to the detector ID input from the detector control unit 36 into a digital signal, and detects the detector control unit. To 36.

(Data correction function)
The detector control unit 36 corrects the detection time information input from the timing detection unit 35 by, for example, a method described in Japanese Patent Application Laid-Open No. 2005-249806 based on the peak value acquired via the ADC 25. . Further, the gain and offset correction of the detector 21 and the analog ASIC 24 are performed on the peak value input from the ADC 25 based on calibration data collected in advance.

(Packet data generation function)
The detector controller 36 uses the corrected peak value as detected energy value information, adds the corrected detection time information and detector ID to the detected energy value information, and adds packet data (detected γ-ray information) as digital information. , Detected radiation information) is generated and output to the data transfer unit 37.

(Data transfer part)
The data transfer unit 37 is an input / output integration function that combines a plurality of input systems into one output system, and a buffer memory function that temporarily stores input packet data and outputs it according to the processing speed of the subsequent components And have. When the packet data is input from each detector control unit 36, the data transfer unit 37 buffers the packet data as necessary, and periodically outputs 12 pieces of packet data output from each detection signal processing unit 34, for example. Is transmitted to a unit-integrated FPGA (Field Programmable Gate Array, hereinafter referred to as FPGA) 31 provided outside the housing 30 of the detector unit 2 (see FIG. 9) containing the combined substrate 20.

(Unit integrated FPGA)
The FPGA 31 includes a buffer function that once receives packet data from the digital ASIC of all the combined substrates 20 accommodated in the detector unit 2, a sort processing function that arranges the packet data in time order based on the detection time information, and a detector. A function of performing scattered radiation processing on the detection of scattered γ-rays detected between the detectors 21 included in the unit 2.

A detailed description of the sort processing function and the scattered radiation processing function will be described later in the description of the sorting processing function and the scattered radiation processing function of the FPGA 31 and the data collection unit 3. The sort processing functions of the FPGA 31 and the data collection unit 3 have different processing capabilities and circuit scales, but these components include a function unit that sorts a plurality of packet data, and basically follow the same principle. . Therefore, the FPGA 31 and the data collection unit 3 can have a circuit configuration based on the same basic concept. Specific examples of the function unit of the sort process in these components will be described exemplarily when the configuration of the FPGA 31 is described later.
The FPGA 31 transmits the packet data to the data collection unit 3 via the information transmission wiring connected to the connector 38. For example, four data collection units 3 (see FIG. 2) are arranged in the circumferential direction, and packet data from the detector units 2 that are divided into four groups in the circumferential direction are collected and collected in one data collection unit 3. Then, the scattered processing is performed by sorting, and then transmitted to the data processing device 12.

(Detector unit; unitized by storing the coupling board)
Next, unitization by storing the combined substrate 20 in the housing 30 will be described.
As shown in FIG. 9, the detector unit 2 transmits and receives signals to and from the twelve coupling substrates 20, the high-voltage power supply devices PS and FPGAs 31 that supply charge collecting voltages to the twelve coupling substrates 20. A housing 30 (see FIG. 10) for housing and holding a connector for signals to be performed, a power connector for receiving power supply from the outside, and the like are provided.

  As shown in FIGS. 9 and 10, the bonding substrates 20 are arranged in three rows so as not to overlap in the depth direction (the body axis direction of the subject P), and four in the circumferential direction of the camera 11. It is contained within. That is, 12 coupling substrates 20 are accommodated in one housing 30. In order to store the guide member 39 in this way, a guide member 39 having four rows of guide grooves G1 extending in the depth direction and appropriately spaced in the circumferential direction is attached to the upper end portion of the housing 30. The guide member 39 has an opening 40 at a position facing each connector C3 of the top plate 30a in each guide groove G1.

  Further, four guide members 41 having one guide groove G2 extending in the depth direction are attached to the upper surface of the bottom plate 30b of the housing 30 so as to be appropriately separated in the circumferential direction (see FIG. 10). The guide grooves G <b> 1 and G <b> 2 have a depth enough to accommodate three coupled substrates 20. The end of the coupling substrate 20 on the ASIC substrate 20B side is inserted into the guide groove G1, and the end of the coupling substrate 20 on the detector substrate 20A side is inserted into the guide groove G2. Three coupled substrates 20 are held side by side in the depth direction of the guide grooves G1 and G2.

  Incidentally, since the coupling substrate 20 is configured such that the end portion on the ASIC substrate 20B side and the end portion on the detector substrate 20A side slide in the guide grooves G1 and G2, the coupling substrate 20 is moved with the fingers or the like to the guide groove G1. , G2 can be slid and easily positioned at a predetermined location. At this time, each board connector C2 is located in the opening 40 portion. After the predetermined number of coupled substrates 20 are arranged in the housing 30, the top plate 30 a is detachably attached to the upper end of the housing 30 with screws or the like. Each connector C3 provided on the top plate 30a is inserted into the corresponding opening 40 and connected to the corresponding board connector C2.

  The upper part and the lower part of the casing 30 are when the casing 30 is taken out from the camera 11, and when the casing 30 is provided in the camera 11, as shown in FIG. May be reversed, and the top and bottom may be rotated 90 ° to the left or right, or may be slanted.

  As shown in FIG. 10, the top plate 30 a of the housing 30 is provided with an FPGA 31 and a connector 38 in addition to the four rows of guide grooves G <b> 1 described above. The connector 38 is connected to the FPGA 31. The FPGA 31 can create a program on site. This is different from the ASIC that cannot be programmed. Therefore, as in the present embodiment, the FPGA 31 can appropriately cope with a change in the number of combined substrates even when, for example, the number or type of combined substrates 20 to be accommodated changes.

  Since the detector 21 using CdTe as the semiconductor material S used in the present embodiment generates charges in response to light, the housing 30 is made of a light-shielding material such as aluminum or an aluminum alloy. In addition, there is no gap for light to enter. That is, the housing 30 has a light shielding property. Incidentally, when the light shielding property is ensured by other means, the housing 30 itself does not need to have the light shielding property, and may be a frame (frame body) that detachably holds the detector 21. For example, the housing 30 may have a frame structure, and a light shielding face material or the like may be unnecessary.

  Further, the packet data (all packet data for all detectors 21 of the combined substrate 20) output from the data transfer unit 37 of all the combined substrates 20 in the detection unit 2 is transmitted from the FPGA 31 provided in the detection unit 2 to the data processing device. 12 is sent.

(Power supply)
Next, the high-voltage power supply device PS that supplies a voltage for collecting charges will be described. As shown in FIG. 9, the detector unit 2 has a charge collection voltage applied to each detector 21 in a space formed by a partition wall 30 c made of a conductive metal material in the housing 30 on the back side of the FPGA 31. Is installed. The high-voltage power supply device PS is supplied with a low-voltage power supply, boosts the voltage to 500 V by a DC-DC converter that boosts a voltage (not shown), and supplies the voltage to each detector 21. Incidentally, 64 detectors 21 are provided on one side and 128 on both sides of one detector substrate 20A. Then, twelve bonded substrates 20 are accommodated in one housing 30. Therefore, a voltage is supplied to 128 × 12 = 1536 detectors 21 from the high-voltage power supply device PS.

In the present embodiment, the high-voltage power supply device PS built in the detector unit 2 is connected to the external low voltage (5 to 15 V) DC by the power supply wiring via the power supply connector 42 and the connector 38 provided on the top board 30a. Connected to power. The high-voltage side terminal of the high-voltage power supply device PS is connected to twelve connectors C3 provided on the top plate 30a by high-voltage power supply wires 44 via connectors 43 provided on the top plate 30a. In FIG. 9, only one high-voltage power supply wiring 44 is illustrated as being connected from the connector 43 to the connector C3 by way of example, but actually, the high-voltage power supply wiring 44 is wired from the connector 43 to each connector C3.
The high-voltage power supply is provided on the board body 20a via the connector C3, the board connector C2 of each coupling board 20, the high-voltage power wiring (not shown) in the board main body 20b, and the high-voltage power wiring (not shown) in the connector C1 and the board main body 20a. Each detector 21 is connected to an electrode C. The connectors C1 and C2 include a connector for high-voltage power supply wiring in addition to the connector that transmits the output signal of the detector 21.

Incidentally, the voltage supplied from the connector 38 to the high-voltage power supply device PS is boosted to 500 V by a DC-DC converter (not shown) in the high-voltage power supply device PS, and after being boosted, the voltage passes through the top plate 30a of the housing 30 and is coupled. The whole substrate 20 is supplied to the ASIC substrate 20B → detector substrate 20A → each detector 21. That is, the housing 30 (top plate 30a) includes a voltage supply wiring (not shown) that supplies a voltage from the high-voltage power supply device PS to each coupling substrate 20. In addition, each coupling substrate 20 includes a voltage supply wiring that supplies the voltage supplied from the high-voltage power supply device PS via the substrate connector C <b> 2 to each detector 21.
Note that the high-voltage power supply PS may be directly connected to the high-voltage power supply wiring provided on the substrate body 20a via a connector, not via the top plate 30a. Further, the high voltage power source connector may be arranged separately from the output signal connector of the detector 21.

《Explanation of sort processing function and scattered radiation processing function》
Next, the sort processing function and the scattered radiation processing function in the FPGA 31 and the data collection unit 3 will be described with reference to FIGS.
FIG. 11 is a diagram showing a schematic configuration of the detector unit and the data collection unit. The FPGA 31 provided on the outer surface of the housing 30 of the detector unit 2 includes a first data sorting unit 51 and a first scattered radiation processing unit 53, as shown in FIG. Further, the data collection unit 3 includes a data transfer unit 55, a second data sort unit (inter-unit detection data output unit) 57, and a second scattered radiation processing unit (inter-unit scattered radiation processing unit) 59.
Then, as shown in FIG. 2, the packet data output from the FPGA 31 of each detector unit 2 divided into four groups is the data transfer unit of the data collection unit 3 (3A, 3B, 3C, 3D) for each block. 55 is input. Among the packet data input to the data transfer unit 55, γ rays from the detectors 21 on the counterclockwise half in the circumferential direction of the detector unit 2 located at the counterclockwise end in the circumferential direction in the block. The packet data based on the detection signal is output to the second data sorting unit 57 of the data collection unit 3 adjacent in the counterclockwise direction in the circumferential direction. For example, the data is transferred from the data transfer unit 55 of the data collection unit 3A to the second data sort unit 57 of the data collection unit 3B.
The first data sorting unit 51 and the first scattered radiation processing unit 53 are connected in this order. Further, the data transfer unit 55, the second data sort unit 57, and the second scattered radiation processing unit 59 are connected in this order.

  As will be described later, the first scattered radiation processing unit 53 has a function of performing scattered radiation processing on input packet data and collecting a plurality of packet data resulting from one γ-ray. An example of the scattered radiation processing is described in Japanese Patent Application Laid-Open No. 2003-255048. The output of the first scattered radiation processing unit 53 is input to the second data sorting unit 57 in the data collection unit 3. A plurality of scattered γ-rays caused by one γ-ray are not necessarily detected by the detectors 21 in the same detector unit 2 but are also detected by the detectors 21 in the adjacent detector units 2. There is. For this reason, after the scattered radiation processing is performed by the first scattered radiation processing unit 53, it is transferred to the second data sorting unit 57 in the data collection unit 3 and the scattered radiation processing between the detector units 2 is performed. Further, when the scattered radiation processing between the detector units 2 is performed only by the blocked detector unit 2 input to the data collection unit 3, the scattered radiation processing between the detector units 2 at the block boundary is performed. In order to compensate for this, the packet data of the block boundary detector unit 2 is transmitted between the adjacent data collection units 3, and one data collection unit 3 transmits the block boundary between the detector units 2. Scattered ray processing is performed.

The second data sorting unit 57 of the data collection unit 3 is transmitted from the first scattered radiation processing unit 53 of the detector unit 2 that has been blocked, and is input via the data transfer unit 55 and in the circumferential direction. In a state in which half of the packet data near the boundary of the one-side boundary detector unit 2 belonging to the adjacent data collection unit 3 is combined from the data transfer unit 55 of the adjacent one-side data collection unit 3 These packet data are arranged in the order of detection times and output to the second scattered radiation processing unit 59.
The data transfer unit 55 transmits its own data collection unit to the data transfer unit 55 of the other data collection unit 3 adjacent in the circumferential direction among the packet data transmitted from the detector unit 2 of the block to which the data transfer unit 55 belongs. 3, half of the packet data near the boundary of the detector unit 2 on the other boundary belonging to 3 is transmitted.

  Here, the 11 packet data strings (see FIG. 11) input to the second data sort unit 57 are already arranged in the order of detection times. For this reason, it is possible to arrange the packet data in the order of the detection time only by selecting the packet data string having the earliest detection time from the head and merging it into one line. Therefore, a simple merge sort circuit can be used, the circuit scale can be reduced, and processing can be performed at high speed.

  The second scattered radiation processing unit 59 has the same configuration as the first scattered radiation processing unit 53 and operates on the same principle. The second scattered radiation processing unit 59 performs scattered radiation processing using the input packet data, and among the plurality of packet data resulting from one γ-ray, the first γ-ray of the detector 21 on which the γ-ray is incident. It has a function of grasping packet data based on the detection signal. The output of the second scattered radiation processing unit 59 is output to the data processing device 12.

(Description of sort processing function)
Next, a detailed configuration of the first data sorting unit and a method for sorting the packet data in order of detection time will be described with reference to FIG. FIG. 12 is a detailed block diagram of the first data sorting unit.
Packet data is input to the first data sort unit 51 from the plurality of digital ASICs 26. In the first data sorting unit 51, four changeover switches 60 and 61 and four data buffers 65 are shown in FIG. 12, but in reality, twelve changeover switches 60, 61 and 12 data buffers 65 are shown. And one unit sort circuit 66.
In the present embodiment, the case where twelve digital ASICs 26 are provided in the detector unit 2 has been described (see FIG. 7), but the number of digital ASICs 26 may be other than twelve. In this case, the numbers of the changeover switches 60 and 61 and the data buffer 65 are all the same as the number of the digital ASICs 26.

  Each data buffer 65 includes two buffers, that is, a first buffer 65a and a second buffer 65b.

  Each changeover switch 60 is connected to one input terminal of each of the first buffer 65a and the second buffer 65b of one data buffer 65. Each changeover switch 61 is connected to the output terminals of the first buffer 65a and the second buffer 65b of one data buffer 65, respectively. One digital ASIC 26 is connected to one of the first buffer 65 a and the second buffer 65 b of one data buffer 65 by the switching operation of the corresponding changeover switch 60. The unit sort circuit 66 is connected to one of the first buffer 65a and the second buffer 65b of one data buffer 65 by the switching operation of the corresponding changeover switch 61. The output side of the unit sort circuit 66 is connected to the first scattering processing unit 53.

  The function of the first data sorting unit 51 will be specifically described below. The data buffer 65 is a buffer storage device having a function of storing packet data in the order of input, a function of outputting the stored packet data in the order of input, and a function of erasing the stored packet data collectively.

The changeover switch 60 repeats the following switching operations (a1) and (a2) for each time frame, and switches the buffer connected to the digital ASIC 26.
(A1) The changeover switch 60 connects the digital ASIC 26 and the first buffer 65a in a certain time frame. At this time, the digital ASIC 26 is not connected to the second buffer 65b.
(A2) The changeover switch 60 connects the digital ASIC 26 and the second buffer 65b in the next time frame. At this time, the digital ASIC 26 is not connected to the first buffer 65a.

The changeover switch 61 repeats the following operations (b1) and (b2) for each time frame, and switches the buffer connected to the unit sort circuit 66.
(B1) While the changeover switch 60 connects the digital ASIC 26 and the first buffer 65a in a certain time frame, the changeover switch 61 connects the second buffer 65b and the unit sort circuit 66. At this time, the first buffer 65a and the unit sort circuit 66 are not connected.
(B2) In the next time frame, while the changeover switch 60 connects the digital ASIC 26 and the second buffer 65b, the changeover switch 61 connects the first buffer 65a and the unit sort circuit 66. At this time, the second buffer 65b and the unit sort circuit 66 are not connected.

  Therefore, while the first buffer 65 a stores the packet data from the digital ASIC 26, the second buffer 65 b outputs the stored packet data to the unit sort circuit 66. On the contrary, during the period in which the second buffer 65 b stores the packet data from the digital ASIC 26, the first buffer 65 a outputs the stored packet data to the unit sort circuit 66. Since switching is performed in this way, a plurality of packet data are processed continuously even if data processing is performed for each time frame.

  The first buffer 65a (or the second buffer 65b) that has output the stored packet data stores new packet data at the time of changing to the next time frame. Erase all at once. The first buffer 65a and the second buffer 65b preferably have a capacity sufficient to store packet data that is expected to be output from the digital ASIC 26 during one time frame. However, when packet data exceeding the capacity is input to the first buffer 65a (or the second buffer 65b) in the period of one time frame, the packet data exceeding the capacity is discarded. As described above, the first buffer 65a and the second buffer 65b only need to have a practically sufficient capacity, so that the circuit scale can be reduced.

  When the unit sort circuit 66 reads the stored packet data from the first buffer 65a (or the second buffer 65b), the unit sort circuit 66 receives the packet data from the plurality of first buffers 65a (or the plurality of second buffers 65b). It has a function of sequentially outputting in order of detection time. Specifically, the unit sort circuit 66 includes the packet data of each of the twelve first buffers 65a (or the twelve second buffers 65b) that have not yet been read and are located on the most output side. Packet data including the earliest detection time information is retrieved and read. The unit sort circuit 66 adds the read packet data to the end of the packet data string to be output. This packet data string includes a plurality of packet data arranged in order of detection time. As described above, the unit sort circuit 66 repeats the extraction of the packet data including the earliest detection time information and the addition to the end of the packet data string. In the first buffer 65a (or second buffer 65b), a flag indicating that the packet has been extracted is set in the extracted packet data.

  When the first buffer 65a and the second buffer 65b read the packet data located closest to the output end, the first buffer 65a and the second buffer 65b erase this packet data and shift the remaining stored packet data one by one to the output end. You may comprise so that it may be made. Alternatively, a read or unread data address may be held so that the first packet data that has not been read can be discriminated.

  The unit sort circuit 66 collects a predetermined number of packet data read in the order of detection times as described above, and outputs the packet data to the first scattering processing unit 53. Since the unit sort circuit 66 collectively outputs a plurality of packet data arranged in advance in the order of detection times in this way, the processing load can be reduced compared with the case where a large number of packet data are sorted together. The scale can be reduced or the processing speed can be increased.

Next, a detailed configuration and operation of the first scattered radiation processing unit 53 will be described with reference to FIG. FIG. 13 is a detailed configuration block diagram of the first scattered radiation processing unit.
As shown in FIG. 13, the first scattered radiation processing unit 53 includes a pair confirmation unit 85 and a pair generation unit 86. The pair confirmation unit 85 includes a comparison data register 90 including registers 90a to 90e, a comparator 95 including comparators 95a to 95d, and a scattered radiation determination circuit 96. The pair generation unit 86 includes a pair data register 92 including registers 92a to 92e, a data selector 97 including selectors 97a to 97d, and a pair data generation circuit 98.

  The comparison data register 90 stores the registers 90a to 90e from the input end (register 90a) of the first scattered radiation processing unit 53 toward the output end (register 92e) of the first scattered radiation processing unit 53 (that is, in the forward direction). The shift registers are connected in series, and the data stored in the registers 90a to 90e is shifted to the adjacent register in the forward direction every clock. The register 90 a is connected to the output terminal of the first data sort unit 51. The comparator 95a is connected to the registers 90a and 90e. Similarly, the comparator 95b is connected to the registers 90b and 90e, the comparator 95c is connected to the registers 90c and 90e, and the comparator 95d is connected to the registers 90d and 90e.

  The packet data from the first data sort unit 51 is input to the register 90a of the comparison data register 90. The comparison data register 90 is a shift register in which registers 90a to 90e are connected in series, and shifts packet data in the forward direction (toward the register 90e) every time slot in synchronization with the clock.

  The scattered radiation determination circuit 96 has an input terminal connected to the comparators 95a to 95e and an output terminal connected to the registers 90a to 90e.

The scattered radiation determination circuit 96 first reads the detected energy from the detected energy value information of the packet data stored in the register 90e, and the detected energy is in a predetermined energy window provided for the incident γ-ray energy 511 keV. Check whether it is in or not. If it is within the predetermined energy window, the packet data is determined to be detected γ-ray information corresponding to the total energy of 511 keV of the incident γ-ray, and is not subject to subsequent scattered radiation processing. A total absorption flag for discrimination is added to the packet data in the register 90e.
Next, when the total absorption flag is not added, the scattered radiation determination circuit 96 controls the comparator 95 (comparators 95a to 95d), and each of the comparators 95a to 95d corresponds to one of the registers 90a to 90d. Each of the packet data stored in the register 90e and the register 90e is input, and it is determined whether or not the packet data originates from one γ-ray. Specifically, each of the comparators 95a to 95d includes a detector ID and each detection time information that are identifiers that can specify the position of each detector 21 from the corresponding packet data in the corresponding register and register 90e. It is determined whether or not the two packet data are within a predetermined time window and have a detection positional relationship that can be a scattered γ-ray. Further, the comparators 95a to 95d are configured such that the sum of the detected energy values of the two pieces of detected energy value information included in the two packet data to be compared is equal to the energy (511 keV) of the γ rays emitted from the subject P and a predetermined value. It is determined whether or not the energy window ranges are equal.

  Thereafter, the scattered radiation determination circuit 96 receives the determination results of the comparators 95a to 95d, and the number of packet data pairs that satisfy the three determination conditions is one or less, or two or more. Determine whether. When there is one pair of packet data, the scattered radiation determination circuit 96 sets a scattering flag for each packet data stored in the corresponding one of the registers 90a to 90d and the register 90e. Make the data “valid”. When there are a plurality of pairs, the scattering flag is set to “invalid”. That is, an invalid flag is set.

  When the scattered radiation processing is performed, each pair satisfies a detection positional relationship that can be a time window and scattered γ-rays, but the total sum of the detected energy of the pair may not satisfy the energy window condition. The scattered radiation determination circuit 96 does not invalidate the packet data related to these combinations, checks the sum of the detected energy of three or more packet data, and determines whether or not it falls within a predetermined energy window for 511 keV. If they fall within a predetermined energy window, they are combined as scattered rays. The comparator 95 adds a short-distance scattering and a long-distance scattering flag to be described later based on the detector ID of the packet data stored in the register 90e, and the scattered radiation determination circuit 96 is flagged for the short-distance scattering. The combination packet data is preferentially selected, and the packet data related to other combinations is ignored.

  The packet data from the pair confirmation unit 85 is input to the register 92a of the pair data register 92 of the pair generation unit 86. The pair data register 92 is a shift register in which registers 92a to 92e are connected in series, and shifts packet data in the forward direction (toward the register 92e) every time slot in synchronization with the clock. The selector 97a is connected to the register 92a, the selector 97b is connected to the register 92b, the selector 97c is connected to the register 92c, and the selector 97d is connected to the register 92d. The selectors 97a to 97d are connected to the pair data generation circuit 98. The pair data generation circuit 98 is connected to the registers 92a to 92e.

  The pair data generation circuit 98 reads the scattering flag of the packet data input to the register 92e and the invalid detection γ-ray information flag described later. Then, the pair data generation circuit 98 controls the data selector 97 (selectors 97a to 97d) if the invalid detection γ-ray information flag is not set in the packet data and the scattering flag is set, and the paired packet is generated. Data is searched from the registers 92a to 92d. When there is packet data that is a pair or a combination of three, the pair data generation circuit 98 is based on a γ-ray detection signal having the largest detection energy among the packet data that is a pair or a combination of the three. Is the representative detection time information, the detector ID of the detector 21 closest to the body axis of the subject P is the representative detection position (representative detector ID), and packet data resulting from one gamma ray The data is generated and output to the data transfer unit 55 of the data collection unit 3. At this time, the output packet data uses the total value of the detected energy related to the packet data that is a pair or a combination of three as detected energy value information. The pair data generation circuit 98 performs subsequent scattered radiation processing and PET image generation on the packet data stored in the pair data register 92 which is a pair or a combination of three based on the packet data stored in the register 92e. An invalid detection γ-ray information flag, which is an identifier that is not used for the above, is set.

The second data sort unit 57 performs a similar sort process with a simpler sort circuit than the first data sort unit 51 except that the input source and the output destination are different.
The second scattered radiation processing unit 59 has the same configuration as the first scattered radiation processing unit 53 except that the input source and the output destination are different, and performs the same scattered radiation processing.

Next, taking the first scattered radiation processing unit 53 as an example, the procedure of the pair confirmation scattered radiation determination process executed by the scattered radiation determination circuit 96 in the scattering process will be described with reference to FIGS. 14 to 16. .
14 to 16 are flowcharts showing the flow of control of the scattered radiation determination process. The second scattered radiation processing unit 59 also performs similar scattered radiation determination processing.
First, the scattered radiation determination circuit 96 waits until new packet data is shifted to the register 90e in the comparison data register 90 (step S301). After the new packet data is stored in the register 90e, the scattered radiation determination circuit 96 performs each process of Steps S303 to S318 (scattered radiation determination process). When new packet data is stored in the register 90e, the packet data stored in the register 90e is used as reference packet data, and the detection energy of the reference packet data is a predetermined γ-ray energy (511 keV) of incident γ rays. It is checked whether the energy window is within the energy window (step S302).

  If it is within the predetermined energy window (Yes), the total absorption flag is set in the packet data serving as a reference (step S303). Here, the total absorption flag is an identifier in data processing that the detected energy of one packet data corresponds to a predetermined incident energy of γ rays and is not scattered. After step S303, the process proceeds to step S304, and the comparator 95 is not allowed to compare the scattered radiation determination between the packet data to be compared in the comparison data register 90 and the reference packet data. Thereafter, in FIG. 13, the packet data is sent to the right in synchronization with the clock, the scattered radiation determination process for the packet data stored in the register 90e is finished, and the packet data newly stored in the register 90e is used as a reference. The process returns to the scattered radiation determination process using the packet data.

If the energy window is not entered in step S302 (No), the comparator 95 compares the packet data to be compared in the comparison data register 90 with the scattered packet determination of the reference packet data (step S305). .
In step S306, based on the output information from the comparators 95a to 95d, the number of packet data serving as a reference, and the number of packet data determined to match the conditions of the scattered radiation determination time window and the detector positional relationship are 0. It is determined whether or not there is (step S306). Here, the scattered radiation determination time window condition is that the difference in the detection time of the packet data compared to the detection time of the packet data used as a reference is within a predetermined time, and there are a plurality of conditions due to scattering with respect to one incident γ-ray. This means that the detected signal from the detector 21 falls within a time window that can be determined to be substantially the same. The condition of the scattered radiation detector positional relationship is, for example, the positional relationship described in Japanese Patent Application Laid-Open No. 2003-255048.

If the number of packet data determined to match is 0 (Yes), then the packet data is sent to the right in synchronization with the clock in FIG. 13, and the scattered radiation determination for the packet data stored in the register 90e is performed. After the above process is completed, the process returns to the scattered radiation determination process using the packet data newly stored in the register 90e as the reference packet data.
If the number of packet data is not 0 (No), the process proceeds to step S307.
In step S307, it is determined whether or not the number of packet data serving as a reference and the number of packet data determined to match the condition of the scattered radiation determination time window and the detector positional relationship is one. If the number of packet data determined to match the condition is 1 (Yes), the process proceeds to step S308; otherwise (No), the process proceeds to step S313.

In step S308, the sum of detected energies is obtained for the packet data serving as a reference and the packet data determined to match. Next, it is checked whether or not the total detected energy of the corresponding two packet data is within a predetermined energy window (step S309).
When this determination is “No”, the packet data is then sent to the right in synchronization with the clock in FIG. 13, and the scattered radiation determination processing for the packet data stored in the register 90e is completed. The process returns to the scattered radiation determination process using the packet data stored in the register 90e as reference packet data.
When this determination is “Yes”, it is determined whether the detector positional relationship between the two pieces of packet data is short-distance scattering or long-distance scattering. Here, the short-range scatter refers to 3 units of detectors 21 set as a predetermined short-range scatter range (first spatial range) around the detector 21 corresponding to the detector ID of the packet data serving as a reference. This means scattering within a three-dimensional spatial distance, and the long-range scattering means 3 detector units set as a predetermined long-range scattering range (second spatial range) wider than the predetermined short-range scattering range. Means scattering within a dimensional spatial distance.

In the case of short distance scattering, the process proceeds to step S311 and a short distance scattering flag is set for two pieces of packet data. At this time, as the value of the flag, the relative position of the packet data that is considered to be a scattered radiation pair is used as the reference packet data, and the compared packet data (that is, the other packet data in the registers 90a to 90d). ) Is set to “0”.
However, if the short-range scatter flag is already set in the reference packet data, the short-range scatter flag and the long-range scatter flag are invalidated (the flag value is set to “null”). At this time, the short-range scatter flag and the long-range scatter flag may be invalidated only for the reference packet data, and both the reference packet data and the compared packet data are the above-mentioned long-range Both near-field scattering flags may be disabled. In this case, the reference packet data corresponds to the case where the short-range scatter flag is set to “0” when the packet data is compared in the previous cycle step, and the reference in this cycle. This means that packet data having a possibility of a pair of short-distance scattering following itself is found. In that case, both the short-range scatter pair with the packet data that goes back in time from itself, and this time, the pair that has the possibility of short-range scatter following in time with respect to itself, Invalid. This is due to the idea that a pair of packet data that is suspected of being detected as scattered radiation due to one identical γ-ray is not used for the generation of a PET image.
Further, the short-range scatter flag and the long-range scatter flag are set to be invalid for the compared packet data in which the short-range scatter flag is already set (the flag value is set to “null”). This is also based on the idea that a pair of packet data that is suspected of being detected as a scattered ray attributed to one identical γ-ray is not used for generating a PET image.
Thereafter, in FIG. 13, the packet data is sent to the right in synchronization with the clock, the scattered radiation determination process for the packet data stored in the register 90e is finished, and the packet data newly stored in the register 90e is used as a reference. The process returns to the scattered radiation determination process using the packet data.

In the case of long-distance scattering, the process proceeds to step S312 and a long-distance scattering flag is set for two pieces of packet data. At this time, as the value of the flag, the relative position of the packet data that is considered to be a scattered ray pair is set for the reference packet data, and “0” is set for the compared packet data.
However, if the long-distance scattering flag is already set in the reference packet data, the long-distance scattering flag is invalidated (the flag value is set to “null”). At this time, the long-range scatter flag may be invalidated only for the reference packet data, or the long-range scatter flag is invalidated for both the reference packet data and the compared packet data. Also good. This is also based on the idea that, as described above in the description of step S311, a pair of packet data that is suspected of being detected as scattered radiation caused by one identical γ-ray is not used for generating a PET image. .
Further, the far-range scatter flag is set to invalid for the compared packet data in which the long-range scatter flag is already set (the flag value is set to “null”). This is also based on the idea that a pair of packet data that is suspected of being detected as a scattered ray attributed to one identical γ-ray is not used for generating a PET image.
Thereafter, in FIG. 13, the packet data is sent to the right in synchronization with the clock, the scattered radiation determination process for the packet data stored in the register 90e is finished, and the packet data newly stored in the register 90e is used as a reference. The process returns to the scattered radiation determination process using the packet data.

When the process proceeds from step S307 to step S313, the sum of the detected energies is obtained for the reference packet data and all the packet data determined to match. Next, it is checked whether or not the total detected energy of these packet data is within a predetermined energy window (step S314).
When this determination is “No”, the packet data is then sent to the right in synchronization with the clock in FIG. 13, and the scattered radiation determination processing for the packet data stored in the register 90e is completed. The process returns to the scattered radiation determination process using the packet data stored in the register 90e as reference packet data.
When this determination is “Yes”, it is determined whether or not long-distance scattering is included in the positional relationship of the corresponding packet data.

When long-distance scattering is not included (No), the process proceeds to step S316, and a short-distance scattering flag is set for the corresponding packet data. At this time, as the value of the flag, the relative position of a plurality of packet data considered as a scattered ray pair is set in the reference packet data, and “0” is set in the compared packet data.
However, if the short-range scatter flag is already set in the reference packet data, the short-range scatter flag and the long-range scatter flag are invalidated (the flag value is set to “null”). At this time, the short distance scatter flag and the long distance scatter flag may be invalidated only for the reference packet data, and both the reference packet data and the compared packet data are the short distance. The dispersal flag for both the long distance and the long distance may be invalidated. This is due to the idea that a pair of packet data that is suspected of being detected as scattered radiation due to one identical γ-ray is not used for the generation of a PET image.
Further, the short-range scatter flag and the long-range scatter flag are set to be invalid for the compared packet data in which the short-range scatter flag is already set (the flag value is set to “null”). This is also based on the idea that a pair of packet data that is suspected of being detected as a scattered ray attributed to one identical γ-ray is not used for generating a PET image.
Thereafter, in FIG. 13, the packet data is sent to the right in synchronization with the clock, the scattered radiation determination process for the packet data stored in the register 90e is finished, and the packet data newly stored in the register 90e is used as a reference. The process returns to the scattered radiation determination process using the packet data.

When long-distance scattering is included (Yes), the process proceeds to step S317, and it is checked whether all combinations are long-distance scattering. That is, it is checked whether all combinations of the reference packet data and the compared packet data that may be a long-range scatter pair are within the long-range scatter determination distance. If “Yes” in step S317, the process proceeds to step S318, and a long-distance scattering flag is set in the corresponding packet data. At this time, as the value of the flag, the relative position of a plurality of packet data considered as a scattered ray pair is set in the reference packet data, and “0” is set in the compared packet data.
However, if the long-distance scattering flag is already set in the reference packet data, the long-distance scattering flag is invalidated (the flag value is set to “null”). At this time, the long-range scatter flag may be invalidated only for the reference packet data, or the long-range scatter flag is invalidated for both the reference packet data and the compared packet data. Also good. This is also based on the idea that a pair of packet data that is suspected of being detected as a scattered ray attributed to one identical γ-ray is not used for generating a PET image.
Further, the far-range scatter flag is set to invalid for the compared packet data in which the long-range scatter flag is already set (the flag value is set to “null”). This is also based on the idea that a pair of packet data that is suspected of being detected as a scattered ray attributed to one identical γ-ray is not used for generating a PET image.
Thereafter, in FIG. 13, the packet data is sent to the right in synchronization with the clock, the scattered radiation determination process for the packet data stored in the register 90e is finished, and the packet data newly stored in the register 90e is used as a reference. The process returns to the scattered radiation determination process using the packet data.
As described above, a series of various combinations of scattered radiation determination processing is performed.

Next, with reference to FIG. 17, the first scattered radiation processing unit 53 will be exemplified to describe the pair data generation processing in the scattered radiation processing executed by the pair data generation circuit 98 of the pair generation unit 86. FIG. 17 is a flowchart showing the flow of control of pair data generation in the pair data generation circuit. The second scattered radiation processing unit 59 performs a similar pair data generation process.
First, the pair data generation circuit 98 waits until new packet data is shifted to the register 92e in the pair data register 92 (step 401). Next, whether or not the short distance scattering flag of the packet data stored in the register 92e, that is, the reference packet data is set, and the relative position of the packet data considered as a scattered radiation pair is set as the flag value. Whether or not is checked (step S402). If “Yes”, the process proceeds to step S 403, and if “No”, the process proceeds to step S 406. In step S403, it is determined whether or not a short distance scatter flag is set in the packet data of the pair register corresponding to the relative position of the packet data considered to be the scattered radiation pair, and “0” is set as the flag value. To check. If “Yes”, the process proceeds to step S404. If “No”, the packet data is sent to the right in synchronization with the clock in FIG. 13 and the pair data generation for the packet data stored in the register 92e is performed. After the process is completed, the process returns to the pair data generation process using the packet data newly stored in the register 92e as the reference packet data.

In step S404, representative detection time information and representative detector ID are set for a plurality of packet data related to the same γ-ray, the sum of the detection energy of the packet data is set as detection energy, and new packet data is set. Generate and send.
Here, the representative detection time information is detection time information of the packet data having the maximum detection energy among the plurality of packet data related to the same γ-ray, and the representative detector ID is a plurality of the related γ-ray related to the same γ-ray. The position of the detector 21 in the packet data is the detector ID of the detector 21 closest to the body axis of the subject P. At this time, a total absorption flag is set on the generated packet data. After step S404, the process proceeds to step S405, and an invalid detection γ-ray flag is set on the original packet data.
Setting the total absorption flag on the newly generated packet data and setting the invalid detection γ-ray flag on the original plurality of packet data means the completion of the scattered ray processing, and the subsequent second scattered ray processing unit This is because the scattered radiation processing is not performed at 59.
Here, the detection time information is for the packet data having the largest detection energy, as shown in FIG. 19, the timing signal rises earlier as the peak value of the γ-ray detection signal is larger, and the correction amount of the detection time is smaller. This is because the reliability is high.

When the process proceeds from step S402 to step S406, it is checked whether or not the long-range scatter flag of the reference packet data is set and the relative position of the packet data considered to be a scattered radiation pair is set. If “Yes”, the process proceeds to step S407. If “No”, the packet data is sent to the right in synchronization with the clock in FIG. 13 to generate pair data for the packet data stored in the register 92e. After the process is completed, the process returns to the pair data generation process using the packet data newly stored in the register 92e as the reference packet data.
In step S407, it is determined whether or not a long-range scatter flag is set in the packet data of the pair register corresponding to the relative position of the packet data considered to be the scattered radiation pair, and “0” is set as the flag value. To check. If “Yes”, the process proceeds to step S404. If “No”, the packet data is sent to the right in synchronization with the clock in FIG. 13 and the pair data generation for the packet data stored in the register 92e is performed. After the process is completed, the process returns to the pair data generation process using the packet data newly stored in the register 92e as the reference packet data.
This is the end of the description of the series of pair data generation processing.

The first scattered radiation determination of the present invention corresponds to steps S305 to S311 and steps S313 to S316 of the flowchart in the present embodiment, and the second scattered radiation determination corresponds to steps S305 to S310, step S312 and step S313 of the flowchart. S315, step S317, and step S318 correspond.
The scattered radiation determination process (see FIGS. 14 to 16) and the pair data generation process (see FIG. 17) are executed in parallel during one clock for a plurality of packet data.
A specific example of the scattered radiation determination process and the pair data generation process will be described with reference to FIGS.
As shown in FIG. 18, here, in order to simplify the explanation, a two-dimensional short range scattering range and a long range scattering range are set. Two gamma rays (γ1, γ2) having predetermined energy are incident on the detector 21 at substantially the same time, γ1 interacts with the detector 21, γ1A, and γ1B, and γ2 interacts with the detector 21 and γ1a. It is assumed that an interaction of γ1b is performed.
Here, the square frame shown in (a) shows the short-range scattering range set in units of the detector 21 around the detector 21 that detects the γ-ray, and the square frame shown in (b) shows the γ-ray. The long-range scattering range set in units of the detector 21 with the detected detector 21 as the center is shown.

FIG. 19 shows the generation of timing signals (detection times) of γ-ray detection signals γ1A and γ1B derived from incident γ rays and γ1, and timing signals (detection times) of γ-ray detection signals γ1a and γ1b derived from γ2. Shows variation. If the wave height of the detection signal is small due to scattering, the detection signal generation timing (detection time) is delayed. Therefore, in order to use γ-rays caused by these scatterings for image generation, it is necessary to widen the time window to some extent, but in that case, the incident γ-rays (γ1, γ2) having the original predetermined energy are different. Things are also captured in the time window, and the conventional scattered radiation processing method cannot distinguish the γ1A and γ1B pairs from the γ1a and γ1b pairs to perform the scattered radiation processing.
On the other hand, in this embodiment, it can distinguish as follows.

  20 and 21 show, for example, the movement of packet data in each register of the comparison data register 90 and the pair data register 92 according to the clock cycle in the pair confirmation unit 85 and the pair generation unit 86 in the first scattered radiation processing unit 53. FIG. 6 is a diagram for explaining operations of the scattered radiation determination circuit 96 and the pair data generation circuit 98. The horizontal axis corresponds to each register, and the vertical axis represents a periodic step by a clock. Thereafter, the codes of the detector signals γ1A, γ1B, γ1a, and γ1b are used as they are for the codes of the corresponding packet data.

In the first step, the packet data γ1B is input to the pair confirmation unit 85 and stored in the register 90a. At this time, in addition to the γ-ray detection time, the detector ID data, and the detection energy data originally included in the packet data γ1B, flag data serving as a work area for processing scattered radiation is stored. In the present embodiment, since the scattered radiation processing is divided into two, that is, a long distance and a short distance, the flag area has two areas, Near (short distance scattering flag) and Far (far distance scattering flag). (Although there are other areas for the total absorption flag and the invalid detection γ-ray flag described above, they are omitted because they are not directly related to the scattered radiation processing here.)
Each flag data is initially empty. At the head of the input data, no packet data is contained in the register 90e to be compared by the pair confirmation unit 85. Therefore, the scattered radiation determination is not performed in steps 1 to 4, and the packet data is shifted to the next register every time step.

  In the fifth step, the packet data γ1B is stored in the register 90e serving as a reference for comparison. The comparator 95 compares the detection time, detector ID, and detection energy of the packet data γ1B and the subsequent packet data γ1a, γ1b, γ1A, the time difference is within the time window, and the two detection positions are regarded as scattered rays. It is determined whether it exists in a good place or whether the total energy is equal to the energy of a predetermined incident γ ray. In this example, all the data is within the time window, but regarding the detection position, the packet data γ1a and the packet data γ1A are within the long-range scattering range with respect to the reference packet data γ1B. Can be confirmed. In this case, the scattered radiation determination circuit 96 has two pairs of long-distance scattering for the packet data γ1B, that is, packet data γ1a and packet data γ1A, and the determination at step S317 in the flowchart of FIG. “Null” indicating that the scattered radiation determination is invalid is written in all data.

  When the packet data γ1a becomes the reference packet data in the sixth step, the packet data γ1b becomes the only short-distance scattered ray pair. For this reason, the near-field scatter flag (Near) of the reference packet data γ1a is set to a flag value “1” indicating that it is paired with the packet data immediately behind itself, and to the nearness of the packet data γ1b. In the distance flag, a flag value “0” indicating that it is paired with data before itself is set.

  The packet data for which the short distance scatter flag and the long distance scatter flag have been set in the pair generation unit 86 are sequentially sent to the pair generation unit 86. In the tenth step, the leading packet data γ1B is stored in the register 92e of the pair generation unit 86. The packet data γ1B has no short distance scatter flag (Near) and no pair exists. Further, since the long-distance scattering flag (Far) is invalid, new packet data based on the pair data after the scattered radiation processing is not generated. In step 11, the packet data γ1a is stored in the register 92e. Since the short distance scattering flag is set in the packet data γ1a and the value of the flag indicates “1”, it indicates that the packet data of the pair exists one behind the packet data γ1a. Therefore, it is possible to create a pair with the next packet data γ1b in which the short-distance scattering flag is set and the value of the flag indicates “0”. At this time, the pair data generation circuit 98 generates new packet data, sets an invalid γ-ray information flag on the original packet data γ1a and γ1b, and performs subsequent scattered radiation processing and image generation processing. Don't be a target.

In step 12, the packet data γ1b is stored in the register 92e. Come to the top. The packet data γ1b has a short-distance scattering flag, but the value of the flag is “0”, which indicates that there is a forward match, and the invalid γ-ray information flag is also set. New packet data as data is not generated.
By making it possible to set two flags, short-range scatter and long-range scatter in this way, priority is given to short-range scatter processing, and even if long-range scatter processing cannot identify paired packet data Data pair determination is possible.

According to the PET apparatus 1 of the present embodiment, the following effects can be obtained.
Unlike the configuration in which data from the detector unit 2 is directly input to the coincidence counting circuit, in this embodiment, packet data output from the detector unit 2 during one time frame is converted into one buffer (for example, the first buffer). While the data is stored in the buffer 65a), the subsequent processing is performed using the data stored in the other buffer (for example, the second buffer 65b). For this reason, (a) packet data storage and output are alternately shared by the two buffers (65a, 65b), so that processing is possible even if a large number of events occur in the time frame. For this reason, the time frame can be set long, and the counting off of the γ-ray detection signals straddling the time frame can be reduced.
(B) Since the packet data is arranged in advance based on the detection time, the number of packet data to be subjected to coincidence determination is limited, the processing load is reduced, the operation speed is increased, and the circuit scale is reduced. Scale can be achieved.
(C) Since the scattered radiation processing is performed by arranging the packet data in the order of detection time, the number of packet data to be subjected to the scattered radiation processing is limited, the processing load is reduced, the operation speed is increased, and the circuit scale is increased. It is possible to reduce the size, and by adopting more complicated scattered radiation processing logic, it is possible to further reduce the γ-ray detection signals to be missed and improve the sensitivity of the PET apparatus 1.
(D) In the present embodiment, a predetermined short-range scattering range and a long-range scattering range are separately processed in a certain detector unit 2, and then a plurality of detections that are divided into groups and then blocked. Based on the detected γ-ray information obtained on the basis of each γ-ray detection signal from the detector unit 2, the scattered radiation processing is again performed by dividing the predetermined short-range scatter range and the long-range scatter range in the data collection unit 3. Yes. For this reason, the scattered radiation processing in the detector unit 2 is limited to a limited detector signal, and the scattered radiation processing load in the FPGA 31 can be reduced. In addition, the data collection unit 3 only needs to perform scattered radiation processing on the detector unit 2 that has not been determined as short-range scatter or long-range scatter. Scattered ray processing for distance scattering is mainly performed, and the scattered ray processing load for short-distance scattering is reduced.
As a result, the detection unit 2 and the data collection unit 3 have a hierarchical scattered radiation processing configuration for a detection signal with a high count rate, and can be optimized by reducing the scattered radiation processing load of the data collection unit 3. .
In addition, since the short-range scattering is preferentially used in the scattered radiation processing, the number of the γ-ray detection information generated in the accidental same time window is suppressed as the long-range scattering, so noise is suppressed. .

  As a result, a plurality of γ-ray detection signals caused by a single incident γ-ray having a predetermined energy can also be used to create a tomographic image, so that the detection sensitivity of γ-ray is further improved and the inspection time is further shortened. be able to.

In this embodiment, the scattered radiation processing is performed under the two conditions of short-distance scattering and long-distance scattering. However, the setting of the spatial range of the short-distance scattering range and the long-distance scattering range may be changed from two stages to three stages. . In addition, as a condition of short-distance scattering and long-distance scattering, not only the relationship between detector positions, but also the smaller the difference in detection time, the higher the probability that a pair of scattered rays originates from one incident γ-ray, It is also possible to weight by the difference in detection time.
In the present embodiment, in order to reduce the scale of the processing circuit, both the FPGA 31 of the detector unit 2 and the data collection unit 3 perform short-distance and long-distance scattered ray processing, but the present invention is not limited thereto. Even if the short-distance scattered radiation processing is performed by the FPGA 31 and the long-distance scattered radiation processing is performed by the data collection unit 3, it is possible to obtain substantially the same result even if the processing is performed in two stages.
In the present embodiment, the first scattering processing unit 53 and the second scattering processing unit 59 process short-distance scattering and long-distance scattering with one circuit in order to simplify the circuit. And long distance scattering may be processed by separate circuits.

<< Second Embodiment >>
Next, a nuclear medicine diagnostic apparatus according to a second embodiment of the present invention will be described with reference to FIGS. The nuclear medicine diagnosis apparatus of this embodiment is a PET apparatus 1A, which differs from the first embodiment in the following points.
In the present embodiment, the FPGA 31 of the detector unit 2 is replaced with the FPGA 31A (see FIG. 23), becomes the detector unit 2B, exchanges packet data between the detector units 2B, and performs scattered radiation processing between the detector units 2B. Performed with FPGA 31A. Further, the auxiliary data collection unit 4 in the present embodiment shown in FIG. 22 has only a function of transferring data, whereas the data collection unit 3 in the first embodiment performs the scattered radiation processing. The connection to 12 is via the auxiliary data collection unit 4.

About the same structure as 1st Embodiment, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.
As shown in FIG. 23, the detector unit 2B includes an FPGA 31A instead of the FPGA 31 in the detector unit 2.
The FPGA 31A has a function of performing scattered radiation processing, and includes a first data sorting unit 80, a first scattered radiation processing unit 81, a second data sorting unit 82, a second scattered radiation processing unit 83, and a scattered radiation data processing unit 84. I have. The first data sorting unit 80, the first scattered radiation processing unit 81, the second data sorting unit 82, the second scattered radiation processing unit 83, and the scattered radiation data processing unit 84 are connected in this order. A plurality of digital ASICs 26 are connected to the first data sorting unit 80. In the first and second detector units 2B adjacent to each other in the circumferential direction of the camera 11 having the detector unit 2B, the first scattered radiation processing unit 81 of the first detector unit 2B is the second detector unit. It is connected to the 2B second data sort unit 82. The second scattered radiation processing unit 83 of the second detector unit 2B is connected to the scattered radiation data processing unit 84 of the first detector unit 2B. In other words, the second detector unit 2B that inputs the output of the first scattered radiation processing unit 81 of the first detector unit 2B and the second scattered radiation processing unit 83 of the first detector unit 2B are input. The third detector unit 2B is arranged so as to sandwich the first detector unit 2B in the circumferential direction.

The first data sorting unit 80 and the first scattered radiation processing unit 81 have the same configuration as the first data sorting unit 51 and the first scattered radiation processing unit 53 in the FPGA 31 in the first embodiment, and have the same principle. Works with. The second data sorting unit 82 and the second scattered radiation processing unit 83 have the same configuration as the second data sorting unit 57 and the second scattered radiation processing unit 59 in the data collection unit 3 in the first embodiment. However, it operates on the same principle.
The first scattered radiation processing unit 81 has a function of performing scattered radiation processing on the input packet data and collecting a plurality of packet data resulting from a single incident γ-ray of predetermined energy. The output of the first scattered radiation processing unit 81 is input to the second data sorting unit 82 in the detector unit 2B and the second data sorting unit 82 in the adjacent detector unit 2B. A plurality of scattered γ-rays resulting from one γ-ray are not necessarily detected by the detector 21 in the same detector unit 2B, but are also detected by the detectors 21 in the adjacent detector unit 2B. There is. For this reason, after the scattered radiation processing is performed by the first scattered radiation processing section 81, the packet data is also transferred to the second data sorting section 82 in the adjacent detector unit 2B.

  The first scattered radiation processing unit 81 of the first detector unit 2B is a partial detector (preferably, the first detector unit 2B) located in a region close to the second detector unit 2B in the first detector unit 2B. One detector region 2B is divided into two equal parts in the circumferential direction, and all detectors (1/1 in the first detector unit 2B) are located in the region close to the second detector unit 2B. 2)), each packet data resulting from the γ-ray detection signal of 21 is output to the second data sorting unit 82 of the second detector unit 2B.

  The second data sorting unit 82 of the second detector unit 2B includes a first scattered radiation processing unit 81 of the second detector unit 2B and a second detector unit adjacent to the detector unit 2B in the circumferential direction. In a state where the respective data packets input from the first scattered radiation processing unit 81 of 2B are combined, the packet data are arranged in order of detection time and output to the second scattered radiation processing unit 83.

  As described above, each second data sorting unit 82 outputs the detector unit 2B to which the second data sorting unit 82 belongs and the packet data collected from the adjacent detector unit 2B in the order of detection time. Here, the two packet data strings input to the second data sorting unit 82 are already arranged in the order of detection time. For this reason, it is possible to arrange the packet data in the order of the detection time only by selecting the data packet sequence having the earliest detection time and merging the data packet into one column. Therefore, unlike the first data sort unit 80, a simple merge sort circuit can be used, the circuit scale can be reduced, and processing can be performed at high speed.

  The second scattered radiation processing unit 83 has the same configuration as the first scattered radiation processing unit 81 and operates on the same principle. The second scattered radiation processing unit 83 performs scattered radiation processing using the input data packet, and among the plurality of data packets caused by one γ-ray, the first γ-ray of the detector 21 on which the γ-ray is incident. It has a function of grasping a data packet based on the detection signal. The output of the second scattered radiation processing unit 83 is input to the scattered radiation data processing unit 84 in the detector unit 2B and the scattered radiation data processing unit 84 in the adjacent detector unit 2B. That is, if the packet data after the scattered radiation processing is that of the detector unit (for example, the second detector unit) 2B to which the second scattered radiation processing unit 83 belongs, If the scattered radiation data processing unit 84 in the unit (for example, the second detector unit) 2B is the packet data of the adjacent detector unit (for example, the first detector unit) 2B, the packet data is transferred. Each is output to the scattered radiation data processing unit 84 in the adjacent detector unit (for example, the first detector unit) 2B.

  The scattered radiation data processing unit 84 has the same configuration and function as the second data sorting unit 82, and arranges the packet data output to the auxiliary data collection unit 4 in the order of detection time data.

As described above, the PET apparatus 1A according to the second embodiment can perform the scattered radiation processing as in the first embodiment, and the data processing apparatus 12 can perform the scattered radiation processing on the data processing apparatus 12 side. Reduce the burden of data processing. In addition, since the packet data is arranged in advance based on the detection time, the number of packet data subject to coincidence determination is limited, the processing load is reduced, the operation speed is increased, and the circuit scale is reduced. Can be planned.
In addition, since the short-range scattering is preferentially used in the scattered radiation processing, the number of the γ-ray detection information generated in the accidental same time window is suppressed as the long-range scattering, so noise is suppressed. .

In the above embodiments, the PET apparatus 1 and the PET apparatus 1A have been described. However, the present invention can also be applied to a gamma camera apparatus. The gamma camera has a two-dimensional functional image obtained and includes a collimator that regulates the incident angle of γ rays.
A configuration of a nuclear medicine diagnosis apparatus combining the PET apparatus 1 or the PET apparatus 1A and the X-ray CT may be used.

It is a perspective view which shows the structure of PET apparatus as a nuclear medicine diagnostic apparatus which concerns on the 1st Embodiment of this invention. It is the figure which showed typically the cross section of the circumferential direction of the camera of the PET apparatus of FIG. 1, and the path | route which transmits packet data to a data processor from a detector unit via a data collection unit. (A) is a partially broken perspective view of a camera showing a configuration for mounting a detector unit to a camera, and (b) is a cross-sectional view showing a detector unit mounted state at the center of the camera. It is a figure which shows typically the structure of a semiconductor radiation detector. (A) is the perspective view which showed typically the component of the semiconductor radiation detector of the laminated structure of FIG. 5, (b) is the perspective view which made the laminated structure combining the component. (A) is the front view which showed the joint substrate which couple | bonded the detector board | substrate and the ASIC board | substrate of the semiconductor radiation detector which concerns on 1st Embodiment, (b) is the side view of the same (a). . It is the block diagram which showed the schematic structure of digital ASIC, and the connection relation of analog ASIC and digital ASIC. It is the block diagram which showed typically the analog signal processing circuit of analog ASIC. It is a see-through | perspective perspective view which shows the structure of the detector unit which accommodated several bonding board | substrates. It is the side view which looked at the detector unit of FIG. 9 in the body axis direction. It is a figure which shows schematic structure of a detector unit and a data collection unit. It is a detailed block diagram of the first data sorting unit. It is a detailed block diagram of the first scattered radiation processing unit. It is a flowchart which shows the flow of control of the process of a scattered radiation determination. It is a flowchart which shows the flow of control of the process of a scattered radiation determination. It is a flowchart which shows the flow of control of the process of a scattered radiation determination. It is a flowchart which shows the flow of control of the pair data generation in a pair data generation circuit. (A) is a schematic diagram which shows a short-distance scattering range, (b) is a schematic diagram which shows a long-distance scattering range. It is a figure explaining a mode that a detection timing signal is output when several incident gamma rays of predetermined energy are scattered in a detector substantially simultaneously and a plurality of gamma ray detection signals are output. It is a figure explaining the scattered radiation process in a 1st scattered radiation process part. It is a figure explaining the scattered radiation process in a 1st scattered radiation process part. Schematic view of a circumferential section of a camera of a PET apparatus as a nuclear medicine diagnosis apparatus according to a second embodiment of the present invention and a path for transmitting packet data from a detector unit to a data processing apparatus via an auxiliary data collection unit. FIG. It is a block diagram of the unit integrated FPGA of the second embodiment.

Explanation of symbols

1, 1A PET equipment (nuclear medicine diagnostic equipment)
2, 2B detector unit 2A unit support member (support member)
3 Data collection unit 11 Camera (imaging device)
11a Lid 11b Opening 12 Data processing device 12A Simultaneous measurement device 12B Tomographic image information creation device 13 Operation console 13a Display device 13b Input operation unit 14 Bed 20, 120 Bonded substrate (unit substrate)
20A, 120A Detector board 20a, 20b Substrate body 20B, 120B ASIC board 21 Semiconductor radiation detector (γ-ray detector)
22 Capacitor 23 Resistor 24, 124 Analog ASIC (integrated circuit, signal processing device)
24A First system 24B Slow system 24a Preamplifier 24b Timing pickoff circuit 24c Threshold control circuit 24d Waveform shaping circuit 24e Peak hold circuit 25, 25A, 25B Analog / digital converter (signal processing device)
26, 126 Digital ASIC (signal processing device, integrated circuit, data generator)
27 High-voltage power supply 30 Housing (housing member)
30a Top plate 30b Bottom plate 30c Bulkhead 31 Unit integrated FPGA (other integrated circuits)
33, 133 Analog signal processing circuit 34, 134 Detection signal processing unit 35 Timing detection unit 36 Detector control unit 37 Data transfer unit 38, 42, 43 Connector 51, 80 First data sorting unit (detection data output unit)
53, 81 First scattered radiation processing unit (scattered radiation processing unit)
55 Data transfer unit 57 Second data sort unit (detection data output unit, inter-unit detection data output unit)
59, second scattered radiation processing section (scattered radiation processing section, inter-unit scattered radiation processing section)
82 Second data sort part (detection data output part)
83 Second scattered radiation processing section (scattered radiation processing section)
211 Detection element C1, C3 connector C2 Board connector PS High voltage power supply

Claims (5)

a plurality of γ-ray detectors that output γ-ray detection signals in response to detection of γ-rays;
A plurality of data generation units for generating detection γ-ray information including detection time information and a detector ID for identifying the γ-ray detector based on the γ-ray detection signal;
A scattered radiation processing unit that performs scattered radiation processing based on the detected γ-ray information,
The scattered radiation processing unit
Among each of the plurality of detected γ-ray information, for each of the detected γ-ray information serving as a reference and the plurality of other detected γ-ray information, based on the detector ID included in the detected γ-ray information serving as the reference, Performing a first scattered ray determination as to whether or not the detected γ-ray information is attributed to the same γ-ray from the γ-ray detector included in the preset first spatial range;
Merging a plurality of the detected γ-ray information based on the first scattered radiation determination,
further,
Among each of the plurality of detected γ-ray information, for each of the detected γ-ray information serving as a reference and the plurality of other detected γ-ray information, based on the detector ID included in the detected γ-ray information serving as the reference, Second scattering of whether or not the detected γ-ray information is caused by the same γ-ray from the γ-ray detector included in the second spatial range set in advance wider than the first spatial range. A nuclear medicine diagnosis apparatus that performs a line determination and merges a plurality of pieces of the detected γ-ray information based on the second scattered radiation determination. further,
A detection data output unit that outputs a predetermined number of the detected γ-ray information output from the plurality of data generation units in the order of the detection time information included in the detected γ-ray information,
The nuclear medicine diagnosis apparatus according to claim 1, wherein the scattered radiation processing unit performs scattered radiation processing based on a plurality of the detected γ-ray information output in order of time. A support member having a plurality of openings in the circumferential direction; and a plurality of detector units that are respectively inserted into the openings and detachably attached to the support member. A storage member having a plurality of unit substrates detachably stored in the storage member;
The unit substrate includes a plurality of semiconductor radiation detectors that receive γ rays, and an integrated circuit that processes γ ray detection signals output from the plurality of semiconductor radiation detectors,
The integrated circuit outputs detected γ-ray information including a detector ID and detection time information for identifying the semiconductor radiation detector that has detected the γ-ray,
further,
The detector unit has another integrated circuit that outputs the detection γ-ray information output from the integrated circuit included in each unit substrate to the outside of the detector unit,
In the other integrated circuit,
A detection data output unit that outputs a predetermined number of the detected γ-ray information output from the integrated circuit included in the unit substrate in the order of the detection time information included in the detected γ-ray information;
A scattered radiation processing unit that performs scattered radiation processing based on a plurality of the detected γ-ray information output in order of the time,
The scattered radiation processing unit
Among the predetermined number of the detected γ-ray information output from the detection data output unit, the detected γ-ray serving as the reference for each of the detected γ-ray information serving as a reference and the plurality of other detected γ-ray information Based on the detector ID included in the information, whether or not the detected γ-ray information is caused by the same γ-ray from the semiconductor radiation detector included in the preset first spatial range. Perform 1 scattered ray determination,
Merging a plurality of the detected γ-ray information based on the first scattered radiation determination,
further,
Among the predetermined number of the detected γ-ray information output from the detection data output unit, the detected γ-ray serving as the reference for each of the detected γ-ray information serving as a reference and the plurality of other detected γ-ray information Based on the detector ID included in the information, the detected γ-ray caused by the same γ-ray from the semiconductor radiation detector included in the second spatial range set in advance wider than the first spatial range A nuclear medicine diagnostic apparatus characterized by performing a second scattered radiation determination as to whether it is information or not, and merging a plurality of the detected γ-ray information based on the second scattered radiation determination. Providing a plurality of data collection units for collecting detected γ-ray information from the other integrated circuits of the plurality of detector units;
The data collection unit outputs a predetermined number of the detected γ-ray information output from the integrated circuit included in the unit substrate of the detector unit in the order of the detection time information included in the detected γ-ray information. Inter-unit detection data output section;
An inter-unit scattered radiation processing unit that performs scattered radiation processing based on a plurality of the detected γ-ray information output in the time order,
The inter-unit scattered radiation processing unit
The detection included in the reference detection γ-ray information for each of the reference detection γ-ray information and the plurality of other detection γ-ray information among the predetermined number of output detection γ-ray information. Based on the device ID, a first scattered radiation determination as to whether or not the detected γ-ray information is attributed to the same γ-ray from the semiconductor radiation detector included in the first spatial range set in advance. Performing a plurality of the detected γ-ray information based on the first scattered radiation determination,
further,
Among the predetermined number of the detected γ-ray information output from the inter-unit detection data output unit, the reference detection is performed for each of the detected γ-ray information serving as a reference and the plurality of other detected γ-ray information. Based on the detector ID included in the γ-ray information, the detection caused by the same γ-ray from the semiconductor radiation detector included in the preset second spatial range wider than the first spatial range 4. The nucleus according to claim 3, wherein a second scattered radiation determination as to whether or not the information is γ-ray information is performed, and a plurality of the detected γ-ray information are merged based on the second scattered radiation determination. Medical diagnostic device. The scattered radiation processing unit includes a first scattered radiation processing unit and a second scattered radiation processing unit,
The first scattered radiation processing unit determines the first scattered radiation with respect to the detected γ-ray information based on the γ-ray detection signals from a plurality of the semiconductor radiation detectors provided in the detector unit of the first scattered radiation processing unit. And determining the second scattered radiation, merging a plurality of the detected γ-ray information based on the first scattered radiation determination and the second scattered radiation determination,
The second scattered radiation processing unit is configured to detect the detected γ-ray information based on the γ-ray detection signals from a plurality of the semiconductor radiation detectors provided in the detector unit of the second scatterer and the other detector units adjacent to the detector unit. Performing the first scattered radiation determination and the second scattered radiation determination, and merging a plurality of the detected γ-ray information based on the first scattered radiation determination and the second scattered radiation determination. The nuclear medicine diagnosis apparatus according to claim 3, wherein the apparatus is a nuclear medicine diagnosis apparatus.

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