Systems and methods for time of flight positron emission tomography
Systems and methods for a time of flight (TOF) positron emission tomography (PET) system is herein provided. In one example, an imaging system comprises one or more detector blocks, each detector block including an array of silicon photomultiplier (SiPM) devices coupled to an array of scintillation crystals with a one-to-one coupling arrangement, wherein each SiPM device of the array of SiPM devices transmits signals to independent front-end readout circuits of one or more analog application-specific integrated circuits (ASICs). The front-end readout circuits are configured to detect individual scintillating photons and suppress SiPM dark counts.
1 . An imaging system, comprising:
a detector block including an array of silicon photomultiplier (SiPM) devices coupled to a crystal in an array of scintillation crystals with a one-to-one coupling arrangement, wherein each SiPM device of the array of SiPM devices transmits signals to independent front-end readout circuits of one or more analog application-specific integrated circuits (ASICs), wherein each independent front-end readout circuit comprises a plurality of comparators and one or more filters, wherein the plurality of comparators are configured with a lowest timing pick-off threshold of ⅓ single photoelectron (SPE).
2 . The imaging system of claim 1 , wherein the detector block forms a portion of a detector ring assembly of the imaging system.
3 . The imaging system of claim 1 , wherein each of the scintillation crystals is optically isolated from each other in the array of scintillation crystals via separating reflectors.
4 . The imaging system of claim 1 , wherein the array of scintillation crystals includes pairs of adjacent scintillation crystals that share light via light sharing reflectors and the pairs are optically isolated from one another via separating reflectors.
5 . The imaging system of claim 4 , wherein information from the pairs of adjacent scintillation crystals provides depth of interaction estimation.
6 . The imaging system of claim 5 , wherein the depth of interaction estimation is applied for timing measurement correction.
7 . The imaging system of claim 1 , wherein the plurality of comparators comprises a first comparator, a second comparator, and an energy comparator.
8 . The imaging system of claim 1 , wherein:
the array of scintillation crystals is an array of bismuth germanate oxide (BGO) scintillation crystals, each BGO scintillation crystal configured to emit Cherenkov light; and
each of the SiPM devices are configured to sense the Cherenkov light emitted by a corresponding scintillation crystal.
9 . The imaging system of claim 1 , wherein each independent front-end readout circuit comprises one or more Time-to-Digital converters (TDCs) and one or more analog to digital converters (ADCs) configured to digitize time-of-arrival, rise time, and energy signals from a corresponding SiPM device.
10 . The imaging system of claim 8 , wherein each independent front-end readout circuit is configured for dark count suppression at 1.5 SPE.
11 . A method for an imaging system, comprising:
sensing light emitted by a scintillation crystal via a silicon photomultiplier (SiPM) device of a detector block in response to an annihilation event;
transmitting an analog signal from the SiPM device to a front-end buffer of a readout circuit;
transmitting the analog signal through an energy channel to an energy filter of the readout circuit and through a timing channel to a timing filter of the readout circuit;
shaping the analog signal with the energy filter and the timing filter of the readout circuit;
comparing the analog signal to one or more thresholds via a plurality of comparators of the readout circuit; and
digitizing the analog signal with one or more time to digital converters (TDCs) and one or more analog to digital converters (ADCs).
12 . The method of claim 11 , further comprising validating the analog signal to suppress dark counts.
13 . The method of claim 11 , wherein the SiPM device is one of a plurality of SiPM devices in an array, wherein each SiPM device in the array is readout by individual readout circuits.
14 . The method of claim 11 , wherein the analog signal comprises a timing signal and an energy signal, and wherein shaping the analog signal with the energy filter and the timing filter of the readout circuit comprises:
shaping the timing signal with the timing filter to make timing pulses from the front end buffer compatible with the timing channel; and
shaping the energy signal with the energy filter to make energy pulses from the front end buffer compatible with the energy channel.
15 . A time of flight (TOF) positron emission tomography (PET) system, comprising:
a detector ring including a plurality of detector blocks, each detector block in the plurality of detector blocks including an array of silicon photomultiplier (SiPM) devices, each SiPM device in the array coupled to one scintillation crystal of an array of scintillation crystals, wherein each crystal of the array of scintillation crystals is configured to emit Cherenkov light in response to interaction with a gamma ray; and
readout electronics including a front-end readout circuit for each of SiPM devices in the array of SiPM devices, wherein the readout electronics are configured to readout signals of detected Cherenkov light,
wherein each front-end readout circuit comprises a timing pick-off circuit and one or more filters, wherein the timing pick-off circuit comprises a plurality of comparators configured to estimate rise time within 1-5 nanoseconds of a pulse, and wherein the readout electronics are configured to be triggered at a first level of ⅓ single photoelectron (SPE) and validated at a second level of 1.5 SPE.
16 . The TOF PET system of claim 15 , wherein each of the array of scintillation crystals is a bismuth germanate oxide (BGO) scintillation crystal.
17 . The TOF PET system of claim 15 , wherein each front-end readout circuit further comprises a front-end buffer and an energy circuit.