Speaker
Dr
Mercedes Rodriguez-Villafuerte
(Instituto de Fisica, UNAM)
Description
Our group is developing a one-ring positron emission tomography prototype for small-animals with detector modules consisting of an assembly of 16×16 LYSO scintillation crystals (1×1×10 mm3) coupled to position sensitive photomultiplier tubes (PS-PMT) Hamamatsu H7546B. The detectors are placed in a ring of 9.8 cm inner diameter, with the object under study positioned on a motorized rotating platform. The 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. Sinograms are obtained from list mode data using different rebinning methods (SSRB, MSRB and FORE), while the tomographic images are obtained with analytical (FBP) and iterative algorithms (ML-EM, OSEM) specifically developed for our prototype. The system matrix is calculated using the GATE v6.0 simulation package assuming a realistic geometry of our experimental set-up. Raw data are corrected for spatial distortion, center of rotation, decay and detector non-uniformities (normalization). Energy resolution for individual crystals was obtained with a uniformly distributed cylindrical 18F source, showing a typical value of 21±3%. Sensitivity was obtained using a 22Na source placed at several axial positions covering the whole extent of the scanner. A maximum absolute sensitivity of 0.24% was obtained at the center of the scanner when using 4 detector modules. Spatial resolution was measured using two line sources (0.6 mm inner diameter) and a glass capillary (1.1 mm inner diameter) placed at different radial positions. A resolution of 1.05 mm was obtained using FORE and ML-EM. A tomographic acquisition of a microDerenzo like phantom (one pie section, 1.25 mm diameter hot rods) was obtained and reconstructed with several reconstruction algorithms. All the hot rods were easily resolved, in agreement with the spatial resolution results obtained with the line sources
Author
Dr
Mercedes Rodriguez-Villafuerte
(Instituto de Fisica, UNAM)
Co-authors
Mr
Alan Miranda-Menchaca
(Instituto de Fisica, UNAM)
Arnulfo Martinez Davalos
(I)
Mr
Tirso Murrieta-Rodriguez
(Instituto de Fisica, UNAM)
