The accuracy of the reconstructed images obtained from a 180.degree. 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.degree. C arc used for reconstruction. Significant distortions are predicted in 201Tl myocardial images reconstructed from both 180.degree. and 360.degree. scans; with signal to noise being significantly better for 180.degree. scans. An anterior 180.degree. scan with a starting angle between right lateral and 45.degree. RAO in 201Tl myocardial imaging is recommended. Reconstructed images acquired from 180.degree. and 360.degree. elliptical orbits are predicted to show more distortion than those obtained from circular acquisitions.