A bound on the energy resolution required for quantitative SPECT

Scattered radiation is one of several physical perturbations that limit the accuracy of quantitative measurements in single-photon emission computed tomography (SPECT). Improvement in detector energy resolution leads to a reduction of scatter counts and a corresponding improvement in the quantitative accuracy of the SPECT measurement. In this study, simulated SPECT projections of a simple myocardial perfusion phantom were used to investigate the effect of detector energy resolution on the data. The phantom consists of a spherical shell of radionuclide within a 15 cm radius water-filled cylinder. Each projection contains on the order of 3 x 10(5) counts. The results demonstrate that a full-width, half-maximum energy resolution of 3-4 keV is sufficient to render the error due to scatter insignificant compared to the uncertainty due to photon statistics in this case. Further simulations verify that because smaller objects produce less scatter, they can be imaged accurately with degraded energy resolution. These results are useful when designing prototype systems that utilize solid-state detectors and low-noise electronics to achieve improved energy resolution.