Fundamentals of 180 degree acquisition and reconstruction in SPECT imaging.

The accuracy of the reconstructed images obtained from a 180 degrees SPECT acquisition is directly related to the effects of resolution and attenuation in the acquired projection data. Computer simulation studies show that the tomographic point spread functions and the quality of 201Tl myocardial perfusion transaxial images depend upon the specific 180 degrees arc used for reconstruction. Significant distortions are predicted in 201Tl myocardial images reconstructed from both 180 degrees and 360 degree scans; with signal to noise being significantly better for 180 degree scans. An anterior 180 degrees scan with a starting angle between right lateral and 45 degrees RAO in 201Tl myocardial imaging is recommended. Reconstructed images acquired from 180 degrees and 360 degree elliptical orbits are predicted to show more distortion than those obtained from circular acquisitions.