Comparison of cone beam and parallel beam collimation with the heart on the axis of rotation for human cardiac SPECT imaging

SPECT is used for imaging human organs like the heart and brain. In clinical cardiac studies the patient is centered on the axis of rotation (AOR) and scanned. For cone beam collimation (CB) the heart might not be in the field of view (FOV) at all angles. To always maintain the heart in the FOV, the heart may be placed on the AOR. But the body size limits the complete circular orbit resulting in incomplete sampling. This may be compensated by combining CB data with parallel beam (PB) data. A phantom was scanned with and without the heart on the AOR using CB and PB collimator. The projection data were analyzed for sensitivity, contrast and signal to noise ratio to compare CB and PB collimation. Results show that CB has better signal to noise, higher sensitivity and better contrast than PB when the heart is on the AOR. Placing the heart on AOR and using CB data might result in better images.