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Simulation study on the performance of time-over-threshold based positioning in monolithic PET detectors
Charlotte Thyssen1,2, Karel Deprez2, Pieter Mollet2
1Medical Image and Signal Processing (MEDISIP), Ghent University, Ghent, Belgium.
Physics in Medicine and Biology
|December 7, 2021
Summary
This study introduces a novel time-over-threshold (ToT) readout for monolithic PET detectors, offering a compact and power-efficient alternative to traditional pulse-integration methods. The ToT approach demonstrates comparable spatial resolution and uniformity, crucial for advanced PET imaging.
Area of Science:
- Medical Imaging
- Detector Physics
- Nuclear Instrumentation
Background:
- Current pixelated PET detectors face resolution limits due to pixel size.
- Monolithic PET detectors offer higher resolution but require advanced readout electronics.
- Existing pulse-integration readout methods are bulky, power-hungry, and expensive.
Purpose of the Study:
- To investigate a novel time-over-threshold (ToT) readout and event positioning scheme for monolithic PET detectors.
- To evaluate the positioning accuracy, uniformity, and performance of the ToT scheme using Monte Carlo simulations.
- To compare the ToT approach with the established mean nearest neighbour (mNN) pulse-integration method.
Main Methods:
- Implemented a time-over-threshold (ToT) readout measuring pulse width above a comparator threshold for event positioning.
- Utilized a mean nearest neighbour (mNN) approach for positioning based on pulse widths.
- Performed Monte Carlo simulations to assess positioning accuracy, uniformity, and bias.
- Investigated the impact of varying threshold values on detector performance.
- Compared ToT results against a sub-mm resolution mNN pulse-integration detector.
Main Results:
- The ToT scheme showed minimal degradation in spatial resolution and bias compared to mNN pulse-integration.
- Highest thresholds resulted in the worst resolution, but degradation remained below 0.1 mm.
- Bias performance was largely constant across thresholds and nearly identical to mNN.
- The ToT detector demonstrated good uniformity and accurate positioning of scattered photons.
- The ToT approach offers advantages in power consumption, compactness, and inherent amplitude-to-time conversion.
Conclusions:
- Time-over-threshold (ToT) is a viable and advantageous alternative to pulse-integration for monolithic PET detectors.
- The ToT method enables lower power consumption, increased compactness, and simplified readout electronics.
- This novel approach has significant implications for the future development of PET detectors.
