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Delay grid multiplexing: simple time-based multiplexing and readout method for silicon photomultipliers.
Jun Yeon Won1, Guen Bae Ko, Jae Sung Lee
1Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul 03080, Korea. Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 03080, Korea.
This study introduces a novel time-based system for simplifying silicon photomultiplier (SiPM) circuits in positron emission tomography (PET) detectors. The method uniquely identifies SiPM positions using time difference of arrival, enabling clearer crystal resolution and potential advancements in time-of-flight PET scanners.
Area of Science:
- Medical Imaging
- Nuclear Instrumentation
- Signal Processing
Background:
- Positron Emission Tomography (PET) scanners require sophisticated systems for detecting gamma rays and determining their origin.
- Current multiplexing and readout methods in PET detectors can be complex and costly.
- Silicon Photomultipliers (SiPMs) are crucial components in modern PET detectors, but their integration presents challenges.
Purpose of the Study:
- To propose and validate a fully time-based multiplexing and readout method for SiPM channels.
- To simplify the electronic circuitry for PET detectors by leveraging time-of-arrival information.
- To enhance the performance of Time-of-Flight (TOF) PET scanners through improved signal processing.
Main Methods:
- A novel time-based multiplexing technique inspired by the Global Positioning System (GPS) was developed.
- Position information was encoded using inherent transit time differences across a delay grid connecting SiPM channels to readout channels.
- Time-of-Arrival (TDOA) measurements and Time-over-Threshold (ToT) for energy extraction were utilized with a Field-Programmable Gate Array (FPGA) Time-to-Digital Converter (TDC).
Main Results:
- A prototype PET detector with 16 LGSO crystals and SiPMs was constructed and tested.
- The proposed method successfully resolved all 16 crystals using only time information from four readout channels.
- Coincidence Resolving Times (CRTs) of 382 ps FWHM (waveform sampler) and 406 ps FWHM (FPGA-TDC) were achieved.
Conclusions:
- The proposed time-based multiplexing and readout method offers a simplified approach for PET detector electronics.
- This technique effectively identifies SiPM positions and extracts energy information, crucial for TOF-PET imaging.
- The demonstrated clarity in crystal resolution and achieved CRTs show promise for developing more efficient and cost-effective TOF-PET scanners.
