Comparing different geometries and reconstruction algorithms for multiple pinhole cardiac SPECT using NCAT

Cardiac SPECT is primarily used for myocardial perfusion imaging for an estimated 9-10 million patients in the US (and approximately double the number worldwide). However SPECT in general suffers from low sensitivity because of the necessity for collimation. Recently, new designs have emerged with 5-8 times the sensitivity of the standard gamma cameras currently used in the clinic for estimating myocardial perfusion. Examples are DSPECT and GE Discovery systems. Pin-hole collimation is used in the new Discovery series from GE. The advantage of this particular pin-hole design is that there are no moving parts, thus reducing manufacturing and servicing costs. Funk et al used a multi-pinhole system attached to a NaI crystal detector for SPECT Cardiac application. This author had proposed curved detector fitted to each pin- hole, to obtain improved performance (~2.25 times sensitivity or 30% better resolution) over that of a flat-detector system for SPECT gamma-cameras. In this work the author implemented voxel-based and detector-based reconstruction algorithms for a multi-pinhole system with flat or curved detectors. Three different geometric configurations with 32, 27, and 21 pinholes were tested and different algorithms compared. The system with 21 pinholes offered similar image quality as the 32 or 27 and was preferred for the reduced number of pinholes. Quantitative analyis was done with the NCAT and a cubic block. The voxel-based reconstruction was preferred from convergence, image quality and speed.