WO2019019450A1

WO2019019450A1 - Gain correction device for digital pet detector

Info

Publication number: WO2019019450A1
Application number: PCT/CN2017/108105
Authority: WO
Inventors: 刘彤; 华越轩; 牛明; 谢庆国
Original assignee: 苏州瑞派宁科技有限公司
Priority date: 2017-07-25
Filing date: 2017-10-27
Publication date: 2019-01-31
Also published as: CN107238854A

Abstract

A gain correction device for a digital PET detector. The device comprises a photoelectric conversion module (100) and a gain self-adaptation module (200), wherein the photoelectric conversion module (100) is in a communication connection with the gain self-adaptation module (200) and sends a scintillation pulse signal to the gain self-adaptation module (200); the gain self-adaptation module (200) comprises a gain adjustment module (210), an overflow determination module (220) and a gain setting module (230), wherein the gain adjustment module (210) receives and amplifies the scintillation pulse signal; the overflow determination module (220) is in communication connection with the gain adjustment module (210) in order to receive the amplified scintillation pulse signal and determine whether there is a signal overflow condition; when signal overflow occurs for the scintillation pulse signal, the overflow determination module (220) sends an adjustment signal to the gain adjustment module (210) so that the gain adjustment module (210) changes an amplification factor of the scintillation pulse signal; and when overflow does not occur for the scintillation pulse signal, the gain setting module (230) in communication connection with the overflow determination module (220) receives the amplified scintillation pulse signal. This gain correction device for a digital PET detector has a better gain correction effect, a simple design and good extensibility.

Description

Gain correction device for digital PET detector

Technical field

The present invention relates to a signal correcting device in the field of medical devices, and more particularly to a gain correcting device for a digital PET detector.

Background technique

Positron Emission Tomography (PET) systems typically employ a large number of detectors, each of which includes a scintillation crystal and optoelectronic device coupled to each other. The scintillation crystal is used to convert gamma photons into visible light, optoelectronics. The device is configured to convert the visible light into an electrical signal, and the corresponding information of the gamma photon, such as the arrival time, the arrival position, and the energy of the gamma photon, can be obtained by processing the electrical signal through a corresponding electronic design.

Photoelectric devices are particularly important in detectors as components for converting visible light into electrical signals. Currently, optoelectronic devices used in PET systems mainly include photomultiplier tubes, silicon photomultipliers (SiPM), multi-pixel photon counters. (multi-pixel photon counter, referred to as MPPC) and Geiger-mode avalanche photodiode (G-APD). The above-mentioned optoelectronic devices generally have a problem that the gain dynamic range varies greatly, even if the gain of the same type of optoelectronic device is not well maintained, and sometimes the difference is too large. If the above optoelectronic devices are combined into a detector under the same operating conditions or applied to a PET system without taking any measures, the problem of uneven gain of the photovoltaic device will cause deterioration in image quality. Therefore, in actual use, it is necessary to correct the gain of the photovoltaic device.

At present, there are mainly the following methods for correcting the gain of the photovoltaic device. The first type, because the gain of the optoelectronic device is affected by many factors, such as the supply voltage and the operating temperature, it can be based on the relationship between the supply voltage, the operating temperature, or the gain of the optoelectronic device and the corresponding response curve. The operating voltage is changed for gain correction to ensure the uniformity of the gain of the optoelectronic device. Second, the gain correction of the optoelectronic device is done using a light-emitting diode network (Reference Hongdi Li, Yaqiang Liu et al. An Instantaneous Photomultiplier Gain Calibration Method for PET or Gamma Camera Detectors Using an LED Network), which is placed with a light-emitting diode In the gap of the optoelectronic device, the light emitted through the slit enters the crystal and then is dispersed on the optoelectronic device, and finally the gain adjustment is completed in conjunction with the correlation algorithm. Third, select a batch of optoelectronic devices, use one of them as a standard, compare the remaining optoelectronic devices with the standard, and then ensure the gain consistency by adjusting the voltage of the optoelectronic devices. The overall uniformity of the gain. Fourth, the comparator is used to roughly determine the gain of the multi-channel optoelectronic device, and then different thresholds are used to ensure the overall uniformity of the gain (References M. Streun, U. Chavan, et al.Treating the Gain Non-Uniformity of Multi Channel PMTs by Channel-Specific Trigger Levels).

However, the first method and the third method are applicable to a system composed of a single optoelectronic device. If the number of optoelectronic devices increases, the number of units that need to be controlled or corrected increases accordingly, since the corrected operating voltages of each optoelectronic device are not the same. The use of a single supply voltage does not meet all the gain-consistency requirements. At the same time, the power supply of the optoelectronic device will become very complicated when the system is built. For the system using the photomultiplier tube, the high voltage of 500-1000V is required, and its expandability low.

For the second method, since the existing detectors mostly use position-sensitive photomultiplier tubes, SiPM or MPPC arrays, the gaps of the optoelectronic devices are narrow, sometimes even narrow enough to place the LEDs, even if the LEDs are barely placed. Among them, the final result is not satisfactory.

For the fourth method, when applied to a PET detector or PET system, the effect is not very satisfactory. If each optoelectronic device can change the operating voltage according to its gain, in order to maintain stability, for a large number of photoelectric conversion devices, it is necessary to provide a large number of corresponding variable voltage power supplies, and the entire PET system will become very complicated and large. post-maintenance. At the same time, each optoelectronic device in the method requires a threshold, and its back-end circuit processing is cumbersome and difficult to expand.

Because optoelectronic devices have good performance over a range of gains, it is essential to find a simple, efficient, and highly scalable method for PET detectors. The invention proposes a device for performing gain adaptation on a plurality of photoelectric devices of the same kind under the same operating parameter on a detector, so that the gain of all the signals is kept within a general range, thereby increasing the stability of the detector. Sex, uniformity and strong adaptability.

Summary of the invention

It is an object of the present invention to provide a gain correcting device for a digital PET detector, thereby solving the problem that the gain correction effect of the photoelectric device of the PET detector in the prior art is not satisfactory, the design is complicated, and the expansion is poor.

In order to solve the above technical problem, the technical solution of the present invention is to provide a gain correcting device for a digital PET detector, the gain correcting device comprising a photoelectric conversion module and a gain adaptive module, wherein the photoelectric conversion module is communicatively coupled with the gain adaptive module The gain adaptation module sends a flicker pulse signal; the gain adaptation module comprises a gain adjustment module, an overflow judgment module and a gain setting module, wherein the gain adjustment module is communicably connected with the photoelectric conversion module to receive and amplify the scintillation pulse signal; the overflow judgment module and The gain adjustment module is communicatively connected to receive the amplified flicker pulse signal, and the overflow judging module judges whether there is a signal overflow condition according to the size of the received flicker pulse signal. When the flicker pulse signal has a signal overflow, the overflow judging module sends the signal to the gain adjustment module. Adjusting a signal to cause the gain adjustment module to change a magnification of the blinking pulse signal; when the blinking pulse signal has a signal overflow, the overflow determining module sends an adjustment signal to the gain adjustment module to cause the gain adjustment module to change Said magnification scintillation pulse signal; scintillation pulse signal when no overflow, the overflow gain setting module connected to the communication module determines the received pulse signal amplified scintillation.

The gain correction device further includes a data acquisition module, and the data acquisition module is communicably connected with the gain setting module of the gain adaptive module, and the data acquisition module receives the flicker pulse signal processed by the gain adaptive module and digitizes the flicker pulse signal.

The gain correction device further comprises a host computer, and the host computer is communicatively connected with the data acquisition module, and the host computer The scintillation pulse signal digitized by the data acquisition module is collected, and the data packet of the scintillation pulse signal is analyzed and utilized to complete image reconstruction and image analysis.

The photoelectric conversion module comprises a scintillation crystal, a photoelectric conversion device and a circuit network, the scintillation crystal is coupled with the photoelectric conversion device, the scintillation crystal receives the gamma photon and converts the gamma photon into the visible light photon, and the photoelectric conversion device converts the visible photon into the electrical signal, the photoelectric The conversion device is communicatively coupled to the gain adaptive module through a circuit network that converts the electrical signal into a scintillation pulse signal.

The scintillation pulse signal includes a relatively fast rising edge and a relatively slow falling edge that decreases exponentially.

The photoelectric conversion device is a photomultiplier tube, a silicon photomultiplier tube, a multi-pixel photon counter or a Geiger mode avalanche diode.

The gain adaptive module uses a single chip microcomputer, a digital signal processing chip, a central processing unit or a field programmable gate array chip.

The gain adjustment module amplifies the scintillation pulse signal by a factor of 0-1.

The overflow determination module compares the received flicker pulse signal with a preset overflow rate to determine whether there is a signal overflow condition.

The set value of the overflow rate is 0%-10%.

The gain correction device of the digital PET detector provided by the invention has a significant improvement in the gain correction effect compared with the prior art, and the invention makes it unnecessary for the PET system to set different external conditions such as different input voltages according to different optoelectronic devices, It simplifies the design of the PET system and can be better adapted to current PET or PET/CT instruments. At the same time, the invention can be directly integrated into the PET detector to realize the digitization and modularization of the PET detector, simplifying the system design and reducing the complexity of constructing the PET system.

DRAWINGS

1 is a schematic structural view of a gain correcting device of a digital PET detector according to an embodiment of the present invention;

2 is an adaptive flowchart of a gain correcting device of a digital PET detector in accordance with an embodiment of the present invention;

3 is a schematic diagram of signal overflow of a gain correcting device of a digital PET detector in accordance with an embodiment of the present invention;

4 is a schematic diagram of waveform comparison after performing gain adaptation according to the gain correcting device of the digital PET detector of FIG. 3;

Figure 5 is a schematic diagram showing the positional spectrum of a detector according to the prior art;

FIG. 6 is a schematic diagram of a position spectrum after performing gain adaptive processing according to FIG. 5. FIG.

Detailed ways

The invention will be further described below in conjunction with specific embodiments. It is to be understood that the following examples are merely illustrative of the invention and are not intended to limit the scope of the invention.

1 is a schematic structural diagram of a gain correcting apparatus of a digital PET detector according to an embodiment of the present invention. As can be seen from FIG. 1, the gain correcting apparatus of the digital PET detector provided by the present invention includes a photoelectric conversion module 100 and a gain adaptive module 200. The data acquisition module 300 and the host computer 400, wherein the photoelectric conversion module 100 is communicatively coupled to the gain adaptation module 200 and transmits a flicker pulse signal to the gain adaptation module 200; the gain adaptation module 200 receives the flicker from the photoelectric conversion module 100. The pulse signal is subjected to gain adaptive processing on the flicker pulse signal, and the gain adaptive module 200 is communicatively coupled to the data acquisition module 300 and transmits a gain adaptively processed flicker pulse signal to the data acquisition module 300; the data acquisition module 300 receives the gain. The adaptively processed flicker pulse signal is digitally processed, and the data acquisition module 300 is further communicably connected to the host computer 400 to transmit the digitized processed flicker pulse signal to the host computer 400; the host computer 400 passes the relevant data acquisition software. Collect digitally processed flicker Red signal, and the digital signal processing scintillation pulse packet and to perform image reconstruction using analytical image analysis.

More specifically, in FIG. 1, the photoelectric conversion module 100 includes a scintillation crystal, a photoelectric conversion device, and a circuit network, the scintillation crystal is coupled to the photoelectric conversion device, and the scintillation crystal receives the gamma photon to The photoelectric signal is converted into a visible light photon and converted into an electrical signal by a photoelectric conversion device, and the photoelectric conversion device is communicably connected to the gain adaptive module 200 through a circuit network, and the circuit network converts the electrical signal into a scintillation pulse signal. The photoelectric conversion module 100 converts the detected gamma photons into a scintillation pulse signal through a scintillation crystal, a photoelectric conversion device, and a circuit network, the scintillation pulse signal including a relatively fast rising edge and a substantially exponentially decreasing slow falling edge.

According to a further embodiment of the present invention, the photoelectric conversion device in the present invention may be a photomultiplier tube, a silicon photomultiplier tube (SiPM), a multi-pixel photon counter (MPPC), or a Geiger mode avalanche diode (G-APD). This is by way of example only, and not limitation.

The gain adaptation module 200 includes a gain adjustment module 210, an overflow determination module 220, and a gain setting module 230. The gain adjustment module 210 is connected to the circuit network of the photoelectric conversion module 100 and receives a flicker pulse signal, and the gain adjustment module 210 simultaneously blinks. The pulse signal is set to a different magnification. For example, in one embodiment of the present invention, the gain adjustment module 210 can amplify the flicker pulse signal by 0-1 times, and the gain adjustment module 210 sends the amplified flicker pulse signal to the overflow judgment. The module 220 determines whether there is a signal overflow at the top according to the size of the received flicker pulse signal. That is, the overflow determination module 220 is configured to determine whether the magnification set by the gain adjustment module 210 is appropriate, or judge Whether the amplified flicker pulse signal exceeds the data acquisition range, when the flicker pulse signal exceeds the data acquisition range, the overflow judging module 220 sends an adjustment signal to the gain adjustment module 210, and the gain adjustment module 210 reduces the signal gain according to the adjustment signal. It should be noted that under the condition that the amplified scintillation pulse signal does not overflow, the larger the gain, the better the effect. The gain setting module 230 is connected to the overflow determination module 220 and receives the flicker pulse signal at the optimal gain sent by the overflow determination module 220, and the gain setting module 230 applies the optimal flicker pulse signal to the data acquisition module 300.

In the gain adjustment module 210 of the present invention, when the signal gain is lowered, the variable gain operational amplifier (VGA) or the adjustable resistor divider can be used to adjust the signal gain to select linear down or non-linear. Linear down-regulation methods, such as index down-regulation, quadratic function down-scaling, etc.

According to a further embodiment of the present invention, the gain adaptive module 200 of the present invention may employ a single chip microcomputer (MCU), a digital signal processing chip (DSP), a central processing unit (CPU), or a field programmable gate array chip (FPGA). A variety of controllers having operational or control capabilities are merely exemplary and not limiting. The gain adaptation module 200 performs gain adaptive processing on the scintillation pulse signal to cause the scintillation pulse signal to be in a gain stable state, for example, to control the gain of the scintillation pulse signal within a fluctuation range of ±10% or less.

The data acquisition module 300 is configured to digitize the optimal flicker pulse signal sent by the gain adaptive module 200 and perform corresponding processing, for example, using a time digital conversion method to obtain the arrival time of the scintillation pulse signal, and calculating the scintillation pulse signal by using the accumulation method. The energy is calculated by using the weighting method according to the obtained energy information, and the above algorithm is received by the common technology in the art, and details are not described herein. The data acquisition module 300 processes the scintillation pulse signal to obtain digitized data including time, location, energy, and the like, and the digitized data can be transmitted to the host computer 400 through various methods such as Gigabit Ethernet, optical fiber, or wireless.

The host computer 400 receives the digitized data of the scintillation pulse signal through the corresponding data acquisition software, and the host computer 400 performs image reconstruction and image analysis by analyzing and utilizing the digitized data.

2 is an adaptive flowchart of a gain correcting device of a digital PET detector according to an embodiment of the present invention. As can be seen from FIG. 2, the working principle of the present invention is: first, power-on reset of a PET system or detector, Then select whether it is necessary to adaptively process the current working conditions. If it is not needed, it will enter the normal data acquisition mode without adaptive processing; if necessary, the gain will be adaptively processed for all channels, the specific steps are as follows: First, the gain adjustment module 210 sets the gain of the current channel to a maximum. For example, in the present invention, the flicker pulse signal can be amplified by a factor of two. At this time, a certain flicker pulse signal data is acquired, and the overflow judging module 220 calculates the flicker pulse. The overflow rate of the signal determines whether the overflow rate exceeds the set value, and the ideal set value of the overflow rate is 0%. As shown in FIG. 3, if the overflow rate exceeds the set value, the overflow determination module 220 sends the gain adjustment module 210 to the gain adjustment module 210. The signal is adjusted so that the gain adjustment module 210 lowers the signal gain, and the signal gain is adjusted, and the overflow determination module 220 continues to overflow. Determination; if the overflow rate does not exceed the set value, the gain The setting module 230 will save the magnification of the current channel and determine whether the current channel is the last channel of the system. If it is the last channel, normal data acquisition starts; if it is not the last channel, the next channel is selected and The gain adjustment module 210 sets the signal gain of the current channel to the maximum, and repeats the above steps in sequence until the gain adaptive adjustment of the last channel is completed, and the normal data acquisition mode is entered. It should be noted that the set value of the overflow rate may be between 0% and 10% depending on the actual conditions used. For example, it may be set to 5% or 10%. It is intended to be illustrative only and not limiting of the scope of the invention.

3 is a schematic diagram of signal overflow of a gain correcting apparatus of a digital PET detector according to an embodiment of the present invention, and FIG. 4 is a schematic diagram of waveform comparison after performing gain adaptation according to FIG. 3, as can be seen from comparison of FIG. 3 and FIG. The waveform after the gain adaptive processing does not show the chopping phenomenon at the top in Fig. 3.

5 is a schematic diagram of a position spectrum of a detector according to the prior art, wherein the photoelectric device adopts a PSPMT-R8900 model and the working voltage is 900V; FIG. 6 is a schematic diagram of a position spectrum after performing gain adaptive processing according to FIG. It can be seen from the comparison between Fig. 5 and Fig. 6 that under the same conditions, the point in Fig. 5 without gain adaptive processing is concentrated in the middle, which causes the phenomenon that the gain is too high, and the waveform of the scintillation pulse signal has a chopping phenomenon. After applying the position calculation method, the point will be closer to the center; and after the gain adaptive processing in Fig. 6, the points of the position spectrum are clearly arguable.

In summary, the gain correction device of the digital PET detector provided by the present invention has the following beneficial effects:

First, the gain correction effect of the present invention has a significant improvement over the prior art.

Secondly, the present invention makes it unnecessary for the PET system to set external conditions such as different input voltages according to different optoelectronic devices, which greatly simplifies the design of the PET system and can be better adapted to current PET or PET/CT instruments. At the same time, the invention can be directly integrated into the PET detector to realize the digitization and modularization of the PET detector, simplifying the system design and reducing the complexity of constructing the PET system.

Again, the present invention is applicable to a variety of optoelectronic devices, including photomultiplier tubes, silicon photomultiplier tubes, and the like. Applicability and practicality.

Finally, the present invention can automatically adjust the gain according to different radionuclides at the front end, thereby avoiding the phenomenon that the gain of the adjusted gain is insufficient or excessive after replacing the front end radionuclide, and the invention can be automatically adjusted to realize the detector. Best performance. The invention is applicable to various radionuclides, such as F-18 18F-FDG, 18F-FDOPA or 18F-FLT, etc., or O-15 based 15O-H2O, or C-11 based 11C-sodium acetate, 11C- A variety of radioactive positive sources such as choline.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and various modifications may be made to the above-described embodiments of the present invention. That is, the simple and equivalent changes and modifications made in the claims and the contents of the specification of the present invention fall within the scope of the claims of the present invention. What has not been described in detail in the present invention are all conventional technical contents.

Claims

A gain correcting apparatus for a digital PET detector, characterized in that the gain correcting device comprises a photoelectric conversion module and a gain adaptive module, and the photoelectric conversion module is communicably connected to the gain adaptive module and The adaptation module sends a flicker pulse signal; the gain adaptation module includes a gain adjustment module, an overflow determination module, and a gain setting module, wherein the gain adjustment module is communicatively coupled to the photoelectric conversion module to receive and amplify the scintillation pulse a signal; the overflow determination module is communicatively coupled to the gain adjustment module to receive the amplified flicker pulse signal, and the overflow determination module determines whether there is a signal overflow according to the size of the received flicker pulse signal. When the flicker pulse signal has a signal overflow, the overflow judging module sends an adjustment signal to the gain adjustment module to cause the gain adjustment module to change the amplification factor of the flicker pulse signal; when the flicker pulse signal does not overflow The gain in communication with the overflow determination module Given module receiving said amplified signal pulse scintillation.
The gain correction device for a digital PET detector according to claim 1, wherein said gain correction device further comprises a data acquisition module, said data acquisition module and said gain setting module of said gain adaptive module A communication connection, the data acquisition module receiving a flicker pulse signal processed by the gain adaptive module and digitizing the scintillation pulse signal.
The gain correction device of the digital PET detector according to claim 2, wherein the gain correction device further comprises a host computer, wherein the upper computer is communicably connected to the data acquisition module, and the upper computer collects the passing device. The data acquisition module digitizes the processed flicker pulse signal, and parses and utilizes the data packet of the scintillation pulse signal to complete image reconstruction and image division Analysis.
A gain correcting apparatus for a digital PET detector according to claim 1, wherein said photoelectric conversion module comprises a scintillation crystal, a photoelectric conversion device, and a circuit network, said scintillation crystal being coupled to said photoelectric conversion device, said The scintillation crystal receives gamma photons and converts the gamma photons into visible light photons, the photoelectric conversion device converts the visible light photons into electrical signals, and the photoelectric conversion device is communicably connected to the gain adaptive module through the circuit network The circuit network converts the electrical signal into the scintillation pulse signal.
A gain correcting apparatus for a digital PET detector according to claim 4, wherein said scintillation pulse signal comprises a relatively fast rising edge and a relatively slow falling edge exponentially decreasing.
A gain correcting apparatus for a digital PET detector according to claim 4, wherein said photoelectric conversion device is a photomultiplier tube, a silicon photomultiplier tube, a multi-pixel photon counter or a Geiger mode avalanche diode.
The gain correcting apparatus for a digital PET detector according to claim 1, wherein the gain adaptive module comprises a single chip microcomputer, a digital signal processing chip, a central processing unit or a field programmable gate array chip.
The gain correction device for a digital PET detector according to claim 1, wherein the gain adjustment module amplifies the scintillation pulse signal by a factor of 0-1.
The gain correction device for a digital PET detector according to claim 1, wherein said overflow determination module compares said received flicker pulse signal with a preset overflow rate to determine whether there is a signal overflow condition. .
A gain correcting apparatus for a digital PET detector according to claim 9, wherein said set value of said overflow rate is 0% - 10%.