THE RELATIVE IMPORTANCE OF ENERGY RESOLUTION FOR QUANTITATIVE TC-99M SPECT IMAGING

We seek to determine the desired energy resolution for quantitative SP ECT imaging. As the energy resolution of the sytem is improved, the re lative error due to scatter decreases. Yet, at some point the improvem ent becomes inconsequential since the scatter error is small compared to the other physical perturbations in the radionuclide measurement. I n order to estimate the energy resolution at which this condition beco mes true, we used a Monte Carlo code to simulate the emission data fro m a myocardial perfusion phantom. The data were reconstructed using a maximum likelihood code, and the images were analyzed to determine the relative effects of attenuation correction, collimator response compe nsation, noise, and scatter rejection on image quantitation. The simul ations showed that improving the system energy resolution beyond 5 keV offers little benefit for myocardial perfusion studies as judged by t he noise in a 9-pixel ROI. The relevance of this result to other appli cations is also discussed.