Evaluation of a strategy to find personalized, patient-specific injected activity levels for SPECT-MPI

Reduction of radiation dose in SPECT-myocardial perfusion imaging (MPI) has become an important objective. This article reports a strategy to find the optimal dose level for a given patient so that he receives the minimum radiation dose required to maintain the diagnostic accuracy obtained at current clinical dose levels. Clinical SPECT-MPI data with realistic simulated lesions was used to first compute perfusion-defect detection performances using the same dose level for all patients (global dose). Each study was evaluated using the total perfusion deficit (TPD) score provided by the clinically validated Quantitative Perfusion SPECT (QPS) software package, and the defect-detection performances were obtained from a receiver operating characteristics (ROC) study based on the patient perfusion scores. Then, personalized dose levels were found for each patient by determining at what reduced dose level the TPD score deviated from the full clinical-dose TPD. Finally, the perfusion-defect detection performance was computed using the personalized dose levels and compared to those obtained from global dose. Preliminary results suggest that further tracer dose (and hence radiation dose) reduction can be achieved by personalizing the dose levels compared to the global (non-patient specific) dose reduction approach. We found this to be the case for both filtered backprojection (FBP) and ordered subsets expectation-maximization (OS-EM).