Optimized Crystal Surface Treatment for Crosshair Light-Sharing TOF-DOI PET Detector

Yoshida, Eiji; Kang, Han Gyu; Obata, Fujino; Yamaya, Taiga

doi:10.1109/trpms.2023.3255557

Cited by 2 publications

(2 citation statements)

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“…In terms of crystal surface condition, it has been reported that changing some polished crystal surfaces to saw-cut surfaces enhanced light output and CRT (Berg et al 2015, Kim et al 2016, Kang et al 2022. Preliminary findings showed that partial saw-cut surfaces improved the DOI resolution in the CLS PET detector (Yoshida et al 2023). The current fast LGSO crystals were chemically etched on all surfaces and then only one lateral side of the crystal was saw-cut as shown in the photograph in figure 1, and a pair of crystals were optically coupled only at the top with the saw-cut surfaces in between.…”

Section: Crosshair Light-sharing Pet Detectormentioning

confidence: 98%

“…A crosshair light sharing (CLS) PET detector has been previously developed (Yoshida et al 2020(Yoshida et al , 2021a(Yoshida et al , 2021b(Yoshida et al , 2021c(Yoshida et al , 2022(Yoshida et al , 2023) that could discriminate one quarter of the crystals (1.45 × 1.45 × 15 mm 3 ) in a photo sensor by changing the output pattern of a pair of crystals to the photo sensors. The CRT of 293 ps and DOI resolution of 5.3 mm (estimated DOI resolution at 511 keV from 4.7 mm of the 662-keV measured result in terms of photon statistics) (Yoshida et al 2021c) have been achieved by eliminating inter-crystal scattering (ICS) (Degenhardt et al 2007, Ritzer et al 2017, which causes Compton scattering in the detector.…”

Section: Introductionmentioning

confidence: 99%

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Calibration method of crosshair light sharing PET detector with TOF and DOI capabilities

Yoshida,

Obata,

Yamaya

2023

Biomed. Phys. Eng. Express

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Objective. A crosshair light sharing (CLS) PET detector as a TOF-DOI PET detector with high spatial resolution has been developed. To extend that work, a detector calibration method was developed to achieve both higher coincidence resolving time (CRT) and DOI resolution. Approach. The CLS PET detector uses a three-layer reflective material in a two-dimensional crystal array to form a loop structure within a pair of crystals, enabling a CRT of about 300 ps and acquisition of DOI from multi-pixel photon counter (MPPC) output ratios. The crystals were 1.45 × 1.45 × 15 mm3 fast LGSO, and the crystal array was optically coupled to an MPPC array. It is important to reduce as many inter-crystal scattering (ICS) events as possible in advance for the accurate detector calibration. DOI information is also expected to improve the CRT because it can estimate the time delay due to the detection depth of crystals. Main results. Using crystal identification and light collection rate of the highest MPPC output reduces the number of ICS events, and CRT is improved by 26%. In addition, CRT is further improved by 13% with a linear correction of time delay as a function of energy. The DOI is ideally estimated from the output ratio of only the MPPC pairs optically coupled to the interacted crystals, which is highly accurate, but the error is large due to light leakage in actual use. The previous method, which also utilizes light leakage to calculate the output ratio, is less accurate, but the error can be reduced. Using the average of the two methods, it is possible to improve the DOI resolution by 12% while maintaining the smaller error. Significance. By applying the developed calibration method, the CLS PET detector achieves the CRT of 251 ps and the DOI resolution of 3.3 mm.

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