Comparative analysis of full-time, half-time, and quarter-time myocardial ECG-gated SPECT quantification in normal-weight and overweight patients

BackgroundThe introduction of a camera-based dose-reduction strategy in myocardial perfusion imaging (MPI) clinical setting entails the definition of objective and reproducible criteria for establishing the amount of activity to be injected.AimThe aim is to evaluate the impact of count statistics on the estimation of summed-scores (SS), end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF).MethodsData rest/stress ECG-gated SPECT (2-day protocol and 8 MBq·kg−1) were acquired with Bright View gamma camera and Astonish algorithm for 40 normal-weight and 40 overweight patients. Assuming that count statistics of shorter acquisition time may simulate that of lower injected activity, three simultaneous scans (full-time, half-time, and quarter-time scans) were started at the same time but with different acquisition time/projection (30, 15 and 8 seconds).ResultsA significant difference between SS values of half-time and quarter-time stress scans was found for overweight group (P = .006). Post hoc test showed significant differences for ESV (P < .05), EDV (P < .01) and EF (P < .05) between half-time and quarter-time scans for both patient groups.ConclusionsThe reduction of the count-statistics to a quarter of the MPI reference influenced negatively the quantification in overweight patients. The decrease of radiopharmaceutical activity to 25% of the reference seems practicable for normal-weight patients, while it is more appropriate an activity reduction limited to 50% for overweight and obese patients.