• Journal of the Korean Society of Radiology
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• v.13 no.6
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• pp.841-846
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• 2019

Effect of misalignment on the performance was evaluated for the development of time-of-flight(TOF)-PET detector. A pair of TOF-PET detector consists of Lutetium-yttrium oxyorthosilicate(LYSO) scintillation crystal with a volume of 3 mm × 3 mm × 20 mm and Geiger-mode avalanche photodiodes(GAPD) photo-sensor with a active area of 3.07 mm × 3.07 mm. Analog output signals from TOF-PET detector were sent to the pre-amplifier and then fed into the gain adjust circuit for achievement of gain homogeneity for each detector. The amplified signals were recorded and digitized by data acquisition system based on oscilloscope. The effect of the detector misalignment between LYSO and GAPD was examined for four different alignment offsets of 0.0 mm, 0.5 mm, 1.0 mm and 1.5 mm for a pair of TOF-PET detector. The photopeak position decreased from ~400 mV to ~250 mV with increasing detector misalignment. the energy resolution and time resolution were degraded from 11.6% to 16.2%, and from 477 ps to 632 ps, respectively. This study demonstrated that PET detector performance was degraded considerably depending on the detector misalignment, which would be a critical issue for the development of TOF-PET detector.

• Nuclear Engineering and Technology
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• v.44 no.1
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• pp.53-60
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• 2012

The aim of this study was to explore the spatial and energy resolutions of a PET scanner that we have recently developed. The scanner, which consists of six detector modules with 1-layer LGSO crystals, has a hexagonal configuration with a faceto- face distance of 86.4 mm between two opposite PET modules; such properties facilitate the imaging of small animals. A $^{22}Na$ point source was employed to estimate horizontal and vertical spatial resolutions. To assess the energy resolution, a uniform $^{18}F$ cylindrical phantom was scanned. A software-based spectrum analysis of list-mode data was used to assign a local energy window centered on the photopeak position for every single crystal. For the image reconstruction, an ML-EM algorithm was used. The spatial resolutions at the center of the scanner were 0.99 mm in the horizontal direction and 1.13 mm in the vertical direction. The energy resolution averaged over each PMT ranged from 13.3%-14.3%, which gave an average value of 13.8%. These results show that this simple system is promising for small animal imaging with excellent spatial and energy resolutions.