Investigation of 90/spl deg/ dual-camera half-fanbeam collimation for myocardial SPECT imaging

This study investigated several aspects of the use of half-fanbeam collimation with a 90/spl deg/ dual-camera system for myocardial single photon emission computed tomography (SPECT) imaging. The detection efficiency, relative to parallel-hole collimation, was evaluated for a range of focal lengths and radii of rotation (ROR) to determine if there was an optimum focal length, which maximized the detection efficiency. In addition, sinograms were constructed and a simulation study was performed to determine if there was an optimal camera system rotation that maximized the total acquired myocardial counts while providing sufficient angular sampling for the myocardial region. Finally, artifacts in images reconstructed from data acquired over various system rotations were evaluated using simulated and experimental data. There existed an optimal collimator focal length for a given ROR; but it varied with ROR. Relative to parallel-hole collimation, the detection efficiency for half-fanbeam collimation was roughly 20% greater, for cast collimators constructed using the same pins and thickness. The theoretical minimum system rotation for sufficient sampling of the myocardial region ranged from 124/spl deg/ to 148/spl deg/ for RORs ranging from 13 to 25 cm, respectively. The total number of acquired myocardial counts was relatively constant for system rotations of 90/spl deg/ to 360/spl deg/. Myocardial SPECT images reconstructed iteratively with attenuation compensation from half-fanbeam data collected over system rotations ranging from 135/spl deg/ to 360/spl deg/ showed no artifacts in the myocardial region. Based on these results, the authors concluded that there was no single optimum system rotation, but that a system rotation of 180/spl deg/ centered at 45/spl deg/ left anterior oblique was a good, practical minimum rotation. Half-fanbeam collimation is a useful alternative system configuration for myocardial SPECT imaging.