Selection of optimum projection angles in three dimensional myocardial SPECT

The purpose of our research is to develop a new data acquisition scheme for myocardial single photon emission CT with a semiconductor detector. The gamma camera system with a semiconductor detector enables us to measure projection data with arbitrary angles because the detector is smaller than those of the ordinary gamma cameras with a scintillation detector. The proposed data acquisition scheme is to measure projection data with angles where the signal to noise ratio in projection data is relatively high. We assumed that we could measure twenty projections to the heart, i.e., in the x-y plane the positions of the detector were 0, 30, 60 and 90 deg. (anterior to LAO 90 deg.) and in the y-z plane they were 60, 30, 0, -30 and -60 deg. to the x-y plane. Then to reduce the number of projections required for an acceptable quality of images, we carefully decided the minimum number of projections and selected optimum projection angles. The criterion for selecting the projection angle was an integral value of power spectra for each projection. We listed projection angles in descending order according to this integral value and made four projection subsets.