CN114994739A - SiPM time signal reader - Google Patents

Abstract

The purpose of the present invention is to provide a SiPM time signal reader, including: a signal extraction module, a signal buffer module and a signal summing module; the signal extraction module includes an array composed of several SiPMs, each of which includes two SiPMs. Output terminal, wherein the first output terminal is connected in series with a detection resistor; the signal directly drawn from the first output terminal is used as the time signal output by the SiPM; the signal drawn from the first output terminal in series with the detection resistor is used as the first output terminal. output signal, the signal drawn from the second output end of the SiPM is used as the second output signal; the signal buffer module includes several radio frequency amplifiers; the time signal output by each channel of SiPM is introduced into one of the radio frequency amplifiers; the signal The summation module includes an addition and amplification circuit, and the output signal of each of the radio frequency amplifiers is connected to the addition and amplification circuit for combination, and the combined signal is used as the time signal of the SiPM array.

Description

A SiPM time signal reader

technical field

The patent of the present invention relates to the technical field of medical imaging equipment, in particular to a combined reading circuit of SiPM time signals based on a radio frequency amplifier.

Background technique

Positron emission tomography (PET) has been the preferred diagnostic imaging technology for tumors and other diseases. Its principle is to achieve image reconstruction by measuring the energy, time and other information of gamma photon events.

At present, the PET system based on silicon photomultiplier (Silicon Photomultiplier, SiPM for short) has gradually become the mainstream. SiPM is composed of hundreds or thousands of self-quenched single-photon avalanche photodiodes (SPADs) operating in Geiger mode, and its logical structure is shown in Figure 1.

One of the bottlenecks of existing SiPM technology is its timing signal readout circuitry. Since the number of SiPMs in a PET system can be as high as tens of thousands, if the output signals of tens of thousands of SiPMs are read out one-to-one, the hardware resources used in the electronics part will be quite large, and the feasibility is low. The current solution for many systems is to short-circuit the signals of multiple SiPMs and combine them into fewer channels, and then use the subsequent electronic systems for measurement. Although this method can reduce the number of measurement channels required, the direct Combining the signals causes the SiPM's time signal to attenuate and mix more noise into the signal, resulting in degraded time performance. Therefore, it is of great significance to realize a time signal merging and reading circuit that can reduce the attenuation of SiPM time signals after merging and does not introduce too much noise for taking advantage of SiPM and achieving higher temporal resolution.

SUMMARY OF THE INVENTION

In view of the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a SiPM time signal reader, including: a signal extraction module, a signal buffer module and a signal summing module; the signal extraction module includes a plurality of SiPM components. array, each SiPM includes two output terminals, wherein the first output terminal is connected in series with a detection resistor; the signal directly drawn by the first output terminal is used as the time signal output by the SiPM; the first output terminal is connected in series with all The signal derived from the detection resistor is used as the first output signal, and the signal derived from the second output end of the SiPM is used as the second output signal; the signal buffer module includes several radio frequency amplifiers; the time signal output by each SiPM is One of the radio frequency amplifiers is introduced; the signal summation module includes an addition amplifier circuit, the output signal of each of the radio frequency amplifiers is connected to the addition amplifier circuit for combination, and the combined signal is used as the signal of the SiPM array. time signal.

The present invention also provides a SiPM time signal reader, comprising: a signal extraction module, a signal buffer module and a signal summing module; the signal extraction module includes several SiPMs, each of the SiPMs includes a plurality of SPADs, each of which The SPAD has a cathode output terminal and an anode output terminal, and the anode output terminal of the SPAD is connected in series with a fast output capacitor, and the cathode input terminals of the multiple SPADs are connected in parallel as the cathode output terminals of the SiPM; The anode output terminal is connected in parallel as the anode output terminal of the SiPM, the output terminals of the multiple fast output capacitors are connected in parallel as the fast output terminal of the SiPM, and the time signal is drawn from the fast output terminal of the SiPM; the signal The buffer module includes several radio frequency amplifiers; each channel of the time signal is introduced into one of the radio frequency amplifiers; the signal summing module includes an addition and amplification circuit, and the output signal of each of the radio frequency amplifiers is connected to the addition and amplification circuit for processing. Combined, the combined signal is used as the SiPM time signal. The SiPM time signal reader of claim 1, wherein the output terminal of the SiPM comprises a cathode or an anode of the SiPM.

Preferably, in the above-mentioned SiPM time signal reader, the first and/or second output signals are connected to a bias power supply, or connected to an energy readout circuit, or used to locate the source of the signal.

Preferably, in the above-mentioned SiPM time signal reader, the first output terminal is a cathode, and the second output terminal is an anode.

Preferably, in the above-mentioned SiPM time signal reader, the second output terminal is a cathode, and the first output terminal is an anode.

Preferably, in the above SiPM time signal reader, the input end of the radio frequency amplifier is provided with a first capacitor.

Preferably, in the above SiPM time signal reader, the output end of the radio frequency amplifier is provided with a second capacitor.

Preferably, in the above SiPM time signal reader, the adding and amplifying circuit includes an operational amplifier, several independent input resistors and feedback resistors; the output signal of each RF amplifier is connected to the operational amplifier through one of the input resistors amplifier; the feedback resistor Rf is connected across the inverting input terminal and the output terminal of the operational amplifier.

Preferably, in the above-mentioned SiPM time signal reader, the output signal of each of the radio frequency amplifiers is connected to the inverting input terminal of the operational amplifier through one of the input resistors.

Preferably, in the above-mentioned SiPM time signal reader, the non-inverting input terminal of the operational amplifier is connected to a reference voltage signal.

Preferably, in the above SiPM time signal reader, the signal of the cathode output terminal and/or the anode output terminal is connected to a bias power supply, or connected to an energy readout circuit, or used to locate the source of the signal.

Description of drawings

Fig. 1 is the logical structure diagram of SiPM in the prior art;

FIG. 2 is a circuit diagram of the first embodiment of the present invention;

3 is a circuit diagram of a second embodiment of the present invention;

FIG. 4 is a schematic structural diagram of the SPAD adopted by the third embodiment of the present invention;

FIG. 5 is a circuit diagram of a third embodiment of the present invention.

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

FIG. 2 is a schematic circuit diagram of an embodiment of the present invention. The SiPM signal reader of the present invention includes a signal extraction module 1 , a signal buffer module 2 and a signal summation module 3 . The signal extraction module 1 includes several SiPMs. Each SiPM includes a cathode terminal and an anode terminal, and the anode terminal is connected in series with a sense resistor Rs. The signal directly drawn from the anode terminal is used as the time signal output by the SiPM, the signal drawn from the anode terminal connected in series with the detection resistor Rs is used as the anode signal of the SiPM, and the signal drawn from the cathode terminal is used as the cathode signal of the SiPM. The time signal output by each SiPM is connected to the signal buffer module 2 . The cathode signal or anode signal of each SiPM can be connected to a bias power supply to supply power to the SiPM, or connected to an energy readout circuit to measure the energy of the SiPM signal. The cathode or anode signal can also be used to determine which SiPM in the array the signal is from.

The signal buffer module 2 includes several radio frequency amplifiers 21, and the time signal output by each SiPM is independently introduced into one radio frequency amplifier 21, so that the signal can be buffered and amplified in the shortest distance, and the good reverse cut-off characteristic of the radio frequency amplifier can also be used. It can isolate the interference between each SiPM output signal and improve the signal quality. In order to isolate the DC and low-frequency components in the signal and reduce the introduction of noise, capacitors C1 and C2 are respectively set at the input end and the output end of the radio frequency amplifier 21 .

The SiPM signals buffered by the signal buffer module 2 are sent to the signal summation module 3 . The signal summation module 3 includes an addition amplifier circuit, and the addition amplifier circuit includes an operational amplifier, several independent input resistors Rin and feedback resistors Rf. The time signal output from capacitor C2 is connected to the inverting input of the operational amplifier through a separate input resistor Rin. The non-inverting input terminal of the operational amplifier can be grounded, and a reference voltage signal Vref can also be input when a DC bias needs to be provided for the signal. The feedback resistor Rf is connected across the inverting input and output of the operational amplifier. The time signals output by each SiPM are sent to the summing and amplifying circuit for combining. Different magnifications can be achieved by setting the parameters of Rin and Rf, and the combined signal is used as the time signal of the SiPM array. It should be noted that the time signal output from the capacitor C2 can also be connected to the non-inverting input terminal of the operational amplifier through the independent input resistor Rin for in-phase addition and combination, but in comparison, it is better to connect the inverting input terminal. Program.

FIG. 3 is a circuit diagram of a second embodiment of the present invention. The difference from the embodiment in FIG. 1 is that the cathode terminal of each SiPM is connected in series with a detection resistor Rs, the signal directly drawn from the cathode terminal is used as the time signal output by the SiPM, and the signal drawn from the cathode terminal in series with the detection resistor Rs is used as the SiPM. The anode signal of the SiPM, the signal drawn from the anode terminal is used as the cathode signal of the SiPM. The time signal output by each SiPM is also buffered by the signal buffer module 2, and then the buffered SiPM signals are combined and amplified by the signal summation module 3; the cathode signal or anode signal of each SiPM can also be biased The power supply supplies power to the SiPM, or is connected to an energy readout circuit to measure the energy level of the SiPM signal. It can also be used to determine which SiPM in the array the signal is coming from. The implementation manner of the signal buffering module 2 and the signal obtaining modules 3 in the second embodiment is the same as that in the first embodiment, and will not be repeated here.

The difference between the third embodiment of the present invention and the first two embodiments is that the structure of the SPAD unit in the SiPM is different, as shown in FIG. 4 . Each SPAD anode has an integrated fast output capacitor, the outputs of these capacitors are connected in parallel as the fast output of the SiPM, and the time signal is read from the fast output of the SiPM. In this embodiment, the detection resistor Rs can be omitted, and the functions of the anode signal and the cathode signal of each SiPM are the same as those in the first embodiment. A schematic circuit diagram of the third embodiment is shown in FIG. 5 . Fast output mode can improve timing and photon counting applications compared to standard output mode. The signal buffering module 2 and the signal obtaining modules 3 in the third embodiment are the same as those in the previous two embodiments, and will not be repeated.

To sum up, compared with the prior art, the SiPM time signal merging readout circuit of the present invention can greatly reduce the number of required time signal measurement channels while ensuring the quality of the merged time signal, and realize ultra-large-scale SiPM. High-performance time signal measurement of arrays, reducing system cost and complexity.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention.

Claims (11)

1. An SiPM time signal reader, comprising:

the device comprises a signal leading-out module, a signal buffering module and a signal summing module;

the signal leading-out module comprises an array formed by a plurality of SiPMs, each SiPM comprises two output ends, and a first output end is connected with a detection resistor in series; the signal directly led out from the first output end is used as a time signal output by the SiPM; a signal led out after the first output end is connected with the detection resistor in series serves as a first output signal, and a signal led out from a second output end of the SiPM serves as a second output signal;

the signal buffer module comprises a plurality of radio frequency amplifiers; the time signal output by each SiPM is introduced into one radio frequency amplifier;

the signal summation module comprises an addition amplifying circuit, the output signal of each radio frequency amplifier is connected to the addition amplifying circuit for combination, and the combined signal is used as the time signal of the SiPM array.

2. An SiPM time signal reader, comprising:

the device comprises a signal leading-out module, a signal buffering module and a signal summing module;

the signal leading-out module comprises a plurality of SiPMs, each SiPM comprises a plurality of SPADs, each SPAD is provided with a cathode output end and an anode output end, the anode output ends of the SPADs are connected with a quick output capacitor in series, and the cathode input ends of the SPADs are connected in parallel to be used as the cathode output end of the SiPM; the anode output ends of the SPADs are connected in parallel to serve as the anode output end of the SiPM, the output ends of the rapid output capacitors are connected in parallel to serve as the rapid output end of the SiPM, and the time signal is led out from the rapid output end of the SiPM;

the signal buffer module comprises a plurality of radio frequency amplifiers; each of said time signals is introduced into one of said radio frequency amplifiers; the signal summation module comprises an addition amplifying circuit, the output signal of each radio frequency amplifier is connected to the addition amplifying circuit for combination, and the combined signal is used as the SiPM time signal. The SiPM time signal reader of claim 1, wherein an output of the SiPM comprises a cathode or an anode of the SiPM.

3. The SiPM time signal reader of claim 1, wherein the first and/or second output signal is coupled to a bias power supply, or coupled to an energy sensing circuit, or used to locate a signal source.

4. The SiPM time signal reader of claim 1, wherein the first output is a cathode and the second output is an anode.

5. The SiPM time signal reader of claim 1, wherein the second output is a cathode and the first output is an anode.

6. SiPM time signal reader according to claim 1 or 2, characterized in that the input of the radio frequency amplifier is provided with a first capacitance.

7. SiPM time signal reader according to claim 1 or 2, characterized in that the output of the radio frequency amplifier is provided with a second capacitance.

8. The SiPM time signal reader of claim 1 or 2, wherein the summing amplification circuit comprises an operational amplifier, a number of independent input resistors, and a feedback resistor; the output signal of each radio frequency amplifier is connected to the operational amplifier through one input resistor; the feedback resistor Rf is connected across the inverting input terminal and the output terminal of the operational amplifier.

9. The SiPM time signal reader of claim 8, wherein the output signal of each of the radio frequency amplifiers is coupled to the inverting input of the operational amplifier through one of the input resistors.

10. The SiPM time signal reader of claim 9, wherein a reference voltage signal is coupled to the non-inverting input of the operational amplifier.

11. The SiPM time signal reader of claim 2, wherein the cathode output and/or the anode output is signaled to a bias supply, or to an energy sensing circuit, or for locating a signal source.

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