EVALUATION OF THE EFFECTS OF PATIENT ARM ATTENUATION IN SPECT CARDIACPERFUSION IMAGING

It was hypothesized that the use of attenuation correction could compe nsate for degradation in the uniformity of apparent localization of im aging agents seen in cardiac wails when patients are imaged with arms at their sides, Noise-free simulations of the digital MCAT phantom wer e employed to investigate this hypothesis, Four variations in camera s ize and collimation scheme were investigated, We observed that: 1) wit hout attenuation correction, the arms had little additional influences on the uniformity of the heart for 180 degrees reconstructions and ca used a small increase in nonuniformity for 360 degrees reconstructions , where the impact of both arms was included; 2) change in patient siz e had more of an impact on count uniformity than the presence of the a rms, either with or without attenuation correction; 3) for a low numbe r of iterations and large patient size, slightly better uniformity was obtained from parallel emission data than from fan-beam emission data , independent of whether parallel or fan-beam transmission data was us ed to reconstruct the attenuation maps; and 4) for all camera configur ations, uniformity was improved with attenuation correction and, given sufficient number of iterations, it was compatible among different im aging geometry combinations, Thus, iterative algorithms can compensate for the additional attenuation imposed by larger patients or having t he arms on the sides, When the arms are at the sides of the patient, h owever, a larger radius of rotation may be required, resulting in decr eased spatial resolution.