Investigation of 90° dual-detector half-fanbeam collimation for myocardial SPECT imaging

This study investigated the use of half-fanbeam collimation with a 90° dual-detector system for myocardial SPECT imaging. The detection efficiency as a function of focal length was evaluated to determine if an optimal focal length exists. Second, sinograms were constructed and a simulation study was performed to determine if there is an optimal camera rotation which maximizes the total acquired myocardial counts while providing sufficient angular sampling for the myocardial region. Finally, image artifacts for various camera rotations were evaluated using simulated and experimental data. There exists an optimal collimator focal length for a given ROR; it varies with ROR. Relative to parallel collimation, the detection efficiency for half-fanbeam collimation is roughly 20% greater, for the same spatial resolution. The theoretical minimum camera rotation for complete sampling of the myocardial region ranges from 123° to 145° for RORs ranging from 13 to 25 cm, respectively. The total number of acquired myocardial counts is relatively constant for camera rotations of 135° to 360°. Myocardial SPECT images reconstructed iteratively with attenuation compensation from half-fanbeam data collected over camera rotations ranging from 135° to 360° showed no artifacts in the myocardial region. We conclude that a camera rotation of 180° centered at 45° left anterior oblique is a good, practical minimum rotation. Half-fanbeam collimation is a strong alternative system configuration for myocardial SPECT