Optical Simulation and Experimental Assessment with Time–Walk Correction of TOF–PET Detectors with Multi-Ended Readouts

Abstract

As a commonly used solution, the multi-ended readout can measure the depth-of-interaction (DOI) for positron emission tomography (PET) detectors. In the present study, the effects of the multi-ended readout design were investigated using the leading-edge discriminator (LED) triggers on the timing performance of time-of-flight (TOF) PET detectors. At the very first, the photon transmission model of the four detectors, namely, single-ended readout, dual-ended readout, side dual-ended readout, and triple-ended readout, was established in Tracepro. The optical simulation revealed that the light output of the multi-ended readout was higher. Meanwhile, the readout circuit could be triggered earlier. Especially, in the triple-ended readout, the light output at 0.5 ns was observed to be nearly twice that of the single-ended readout after the first scintillating photon was generated. Subsequently, a reference detector was applied to test the multi-ended readout detectors that were constructed from a 6 × 6 × 25 mm3 LYSO crystal. Each module is composed of a crystal coupled with multiple SiPMs. Accordingly, its timing performance was improved by approximately 10% after the compensation of fourth-order polynomial fitting. Finally, the compensated full-width-at-half-maximum (FWHM) coincidence timing resolutions (CTR) of the dual-ended readout, side dual-ended readout, and triple-ended readout were 216.9 ps, 231.0 ps, and 203.6 ps, respectively.

Improving the Timing Resolution of Positron Emission Tomography Detectors Using Boosted Learning—A Residual Physics Approach

“…Recently, they have gained attention [20], [21] as they provide high SR [22], [23], [24] but also offer intrinsic depth of interaction (DOI) capabilities [25], [26], thus reducing parallax errors at reduced costs compared to segmented topologies. While, for example, the γ-positioning strongly profits from the spread detection information, it creates disadvantages for the timing performance due to an enhancement of timewalk effects [27], [28], [29] and jitter in signal-propagation times [30], [31], which deteriorate CTR. Therefore, monolithic detector concepts demand advanced readout algorithms and calibration routines to infer the needed information from the detected optical information.…”

Improving the Timing Resolution of Positron Emission Tomography Detectors using Boosted Learning -- A Residual Physics Approach

“…Recently, they have gained attention [15,16] as they provide high spatial resolution [17][18][19] but also offer intrinsic depth of interaction (DOI) capabilities [20,21] at reduced costs compared to segmented topologies, reducing parallax errors. While, e.g., the γ-positioning strongly profits from the spread detection information, it creates disadvantages for the timing performance due to an enhancement of timewalk effects [22][23][24] and jitter in signal-propagation times [25,26], which deteriorate CTR. Therefore, monolithic detector concepts demand advanced readout algorithms and calibration routines to infer the needed information from the detected optical information.…”