Factors affecting standardized uptake value of ^99mTc-MDP bone SPECT/CT: A phantom study

Currently, state-of-the-art SPECT/CT with 3D reconstruction allows for quantitative data that can be represented as standardized uptake value (SUV). However, there are a number of factors that affect the value. The goal of this study was to investigate the factors affecting SUV of ^99mTc-MDP bone SPECT/CT. A NEMA phantom with ^99mTc-MDP background activity concentration of 18 kBq/ml and tumor to background ratio of 4:1 were studied. The data were acquired based on clinical bone SPECT/CT imaging protocol and OS-EM algorithm with compensation for attenuation, scatter and resolution recovery was applied using 10 subsets and varying iterative numbers from 1 to 5. SUVs (SUV_mean and SUV_max) were measured for each sphere using Q.Metrix software. Moreover, three cut-off frequencies of Butterworth filter including 0.35, 0.48 and 0.65 cycle/cm with order of 10 were investigated at 20 iterative updates. The percentage of difference of both SUVs for each sphere was calculated. Both SUVs tended to increase when the iterative update of the OS-EM and cut-off frequency of Butterworth filter were increased. Measurement of SUVs from SPECT/CT is feasible. However, the iterative update, cut-off frequency and sphere size can affect both SUVs.