Abstract
Introduction: The advanced development of iterative image reconstruction enables the absolute quantification of single-photon emission computerised tomography/computed tomography (SPECT/CT) studies by incorporating the compensation for a collimator–detector response, attenuation, and scatter into the reconstruction process. This study aimed to assess the quantitative accuracy of SPECT/CT based on the different levels of 99mTc activity (low/high) on the standardised uptake value (SUV) measurement for different SUV metrics (SUVmean, SUVmax, SUV0.6 max, and SUV0.75 max). Methods: A Jaszczak phantom equipped with six fillable spheres was filled with low- and high activity phantom setup at 1:4 and 1:10 ( Background:sphere) ratios. The low- and high activity concentration phantom setups consisted of ≈10 and ≈60 kBq/ml background, respectively, at both ratios. The fixed-size volume-of-interest (VOI) based on the diameter of each sphere was drawn on SPECT using various metrics for SUV quantification purposes. Results: The convergence of activity concentration was dependent on the iteration number and application of post-filtering. For the background-to-sphere ratio of 1:10 with low activity concentration, the SUVmean metric showed an underestimation of about 38% from the actual SUV, and SUVmax exhibited an overestimation of about 24% for the largest sphere diameter. Meanwhile, the bias reductions of as much as −6% and 7% for SUV0.6 max and SUV0.75 max were observed, respectively. SUVmax indicated the most accurate reading compared with the others, although points that exceeded the actual value were detected. At 1:4 and 1:10 background, the low activity concentration attained a value close to the actual ratio. Using two iterations, 10 subsets (2i10s) without post-filtering had the best parameter in terms of the most accurate values for reconstruction and provided the best image overall. Conclusion: SUVmax is the best metric in high- or low-contrast ratio phantom with adequate iteration number of at least 2i10s without any post-filtering.