ATTENUATION COMPENSATION IN SINGLE-PHOTON EMISSION TOMOGRAPHY - A COMPARATIVE-EVALUATION

Abstract

Attenuation of photons in single-photon emission tomography (SPECT) makes 3-dimensional reconstruction of unknown radioactivity distributions a methematically intractable problem. Approaches to approximate SPECT reconstruction range from ignoring the effects of photon attenuation to incorporating assumed attenuation coefficients into an iterative reconstruction procedure. A computer-based simulation method was developed to assess the relative effectiveness of attenuation compensation procedures. The method was used to study 4 procedures for myocardial SPECT using an infarct-avid radiopharmaceutical, 99mTc stannous pyrophosphate. Reconstructions were evaluated by 2 criteria: overall (sum-of-squares) accuracy, and accuracy of lesion sizing. For moderate- to high-contrast studies there were no significant differences among the reconstructions by either evaluation criterion; for low contrast ratios the iterative method produced lower sum-of-squares error. The additional expense of the iterative method is not justified under the studied conditions. The approach used here is a convenient tool for evaluating specific SPECT reconstruction alternatives.