Effect of sampling rate during dynamic myocardial CT perfusion on coronary flow reserve and ischemia analysis.

Radiation dose is a major concern in dynamic myocardial CT perfusion scan. The purpose of this study was to investigate the effect of reducing the sampling rate on quantitative and semi-quantitative values. This single-center prospective study included 45 patients with type 2 diabetes mellitus (mean age, 58 ± 10 years [SD]; 30 men). Stress and rest dynamic CT perfusion scans were performed every heartbeat for 25 s. Coronary flow reserve (CFR) was calculated as the ratio of stress to rest myocardial blood flow. The summed difference score (SDS) was evaluated using stress and rest myocardial blood flow. CFR and SDS values were compared using the original dataset (1RR) and datasets with reduced sampling rates of 2 and 3 RR intervals (2RR and 3RR). Simulated effective doses were also compared. The mean CFR using the 1RR dataset was 5.89 ± 2.53, unchanged using the 2RR dataset (5.67 ± 2.42, p = 0.08) and decreased to 5.47 ± 2.45 (p = 0.001) using the 3RR dataset. The median SDS (interquartile range) using the 1RR, 2RR and 3RR datasets were 0 (0, 5.75), 0.5 (0, 7) and 0 (0, 6), respectively, with no difference (p > 0.05). The effective doses simulated using the 2RR and 3RR data were 6.7 ± 1.4 mSv and 5.8 ± 1.3 mSv, respectively, significantly lower than the original dose (9.2 ± 1.8 mSv, p < 0.001). A sampling rate of 2RR might be feasible for both semi-quantitative and quantitative evaluation in dynamic myocardial CT perfusion exams.