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Characterization of a One-Ring Small-Animal PET Prototype

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A Miranda

A Miranda*, T Murrieta, A Martinez, M Rodriguez, Universidad Nacional Autonoma de Mexico, Mexico, Distrito Federal

MO-D-141-3 Monday 2:00PM - 3:50PM Room: 141

Purpose: 1) To experimentally characterize a one-ring small-animal PET prototype currently being developed at Instituto de Fisica, UNAM. 2) To develop a software engine for data rebinning and image reconstruction from list mode raw data.

Methods: The prototype detectors are an assembly of 16x16 LYSO scintillation crystals (1x1x10 mm3) coupled to position sensitive photomultiplier tubes (PS-PMT) Hamamatsu H7546B, placed in a ring of 9.8 cm inner diameter. PS-PMT output signals are reduced with resistive chains and digitized with a multichannel acquisition board based on FPGAs using a coincidence window of 6 ns and 12 bits encoding depth. Corrections for spatial distortions, decay, center of rotation and detector normalization have been implemented and are part of our data processing protocol. Energy resolution is measured for each individual crystal using a normalization phantom (hollow cylinder containing 18F mixed with water). Spatial resolution is measured with line sources at different radial distances. Sinograms are obtained from list mode data using different rebinning algorithms (SSRB, MSRB and FORE). Image reconstruction is performed using analytical (FBP, ART) and iterative algorithms (ML-EM, OSEM). Data analysis and processing have been implemented in MATLAB.

Results: The energy resolution of individual crystals has a typical value of 21±3% around the photopeak. The reconstructions of the line sources show different quality depending on the reconstruction technique used. Among the rebinning methods, FORE shows best results producing a spatial resolution of 1.36 mm when using FBP. FORE followed by ML-EM iterative algorithm provides the best spatial resolution (1.05 mm), but with great computational effort.

Conclusion: A one-ring small-animal PET prototype has been built and characterized in terms of spatial and energy resolution. Different rebinning and reconstruction methods have been successfully implemented. Future work will involve phantoms studies (microDerenzo, NEMA NU4-2008) to determine other performance characteristics.

Funding Support, Disclosures, and Conflict of Interest: DGAPA-UNAM PAPIIT IN105913

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