Feasibility of myocardial perfusion imaging with half the radiation dose in obese patients using ordered-subset expectation maximization with resolution recovery software

Background: We previously described the feasibility of myocardial perfusion imaging (MPI) with nearly half the radiation dose using ordered-subset expectation maximization with resolution recovery (OSEM-RR) processing. This study sought to determine if the findings can be expanded to obese patients. Methods: Fifty obese patients (>100 kg) referred for MPI underwent stress-rest or rest-stress studies with a half dose of Tc-99m sestamibi in a 1-day protocol using OSEM-RR processing. Image quality and clinical results were compared with matched patients (by age, sex, weight, presence/probability of coronary artery disease) evaluated with standard "full-dose" Tc-99m sestamibi, mostly in a 2-day protocol. Dose activities were adjusted individually by weight. Results: Mean Tc-99m activity was 33.4 ± 13.9 mCi in the half-dose group and 60 ± 10 mCi in the full-dose group (P <.0001). Respective mean effective doses per study were 10 ± 4 and 18 ± 3 mSv (P <.0001). Overall image quality was good-to-excellent in 94% of the half-dose group and 80% of the full-dose group (P <.045). There was no between-group difference in rate or size of ischemia or infarction, except for stress left ventricular ejection fraction. Conclusions: MPI with half the radiation dose is feasible in obese patients. Image quality is better than for full-dose MPI, and the procedure can be performed in 1 day.