Determination of Spatial Resolution of Positron Emission Tomograph of Clear PET-XPAD3/CT System

Abstract

Based on The National Electrical Manufacturers Association (NEMA), using the AMINE software to construction of sinograms and using a positron emission source of 22 Na, were made calculations to determine the spatial resolution of a ring array system of phoswich detectors of positron emission tomograph included in the CLEAR PET-XPAD3/CT prototype for small animals, made in the laboratories of CCPM and whose project is led by the research group ImXgam. The radioactive source 22 Na of approximately 9 MBq of activity, with spherical shape and diameter of 0.57mm is immersed in a plexiglas disc that was located at the geometric center of tomographic system with a Field of View (FOV) of 35 mm in the axial and transverse directions. Displacements of radioactive source were performed on the three cartesian axes and was rebuilt a sinogram for each axis. The shape of sinogram allows describe the correct position and the maximum efficiency of each detector. Subsequently, was carried out a scanning in each one of three spatial axes taking enough distance to cover the dimensions of radioactive source. Data for each phoswich detector were recorded. The process was repeated for other axes and then radioactive source was centered with respect to the FOV and were calculated FWHM (Full Width at Half Maximum) and FWTM (Full Width at Tenth Maximum) values and performing statistics of these values with parabolic fitting, the latter setting allows to obtain parameters of spatial resolution of system.

Improvement of image quality using amplitude-based respiratory gating in PET-computed tomography scanning

“…The spatial resolution of PET scanning is inevitably limited by several physical factors. These include positron range and noncollinearity (180° ± 0.25°) effects in the process of detecting annihilation radiation following positron emission due to beta + decay in proton-rich nuclides, depth of interaction effects due to the ring-like geometric detector arrangement, and scattered, multiple and random events occurring in the process of pair detection [64][65][66]. In order to resolve these issues, techniques such as TOF have recently been developed to improve temporal resolution [67,68], and various mathematical algorithms to correct the acquired signal, such as PSF, have been developed to overcome spatial resolution limitations [69].…”