Heterogeneity of SPECT bull´s-eyes in normal dogs: comparison of attenuation compensation algorithms

In normal dogs, SPECT Tc-99m Sestamibi (MIBI) Tl-201 myocardial perfusion images reconstructed with filtered backprojection (FBP) show a large decrease of counts in the septal wall (S) compared to the lateral wall (L). We evaluated the iterative method of Chang at 0 and 1 iterations (Chang0 and Chang1), and the Maximum Likelihood-Expectation Maximization with attenuation compensation (ML-EM-ATN) algorithm on data acquired from 5 normal dogs and from simulated projection data using a homogeneous count-density model of a normal canine myocardium in the attenuation field measured in one dog. Mean counts in the S and L regions were calculated from maximum-count circumferential profile arrays. Our results demonstrate that ML-EM-ATN and Chang1 result in improved uniformity, as measured by the S/L ratio