Detection of serial changes in absolute myocardial perfusion with Rb-82 PET

Serial changes in myocardial perfusion may represent an important marker of disease progression or regression or the effects of therapy for patients w ith coronary artery disease (CAD). Quantitative methods have not been devel oped for the assessment of serial changes in perfusion. The objective of th is study was to use receiver operator characteristic (ROC) analysis to dete rmine the sensitivity and specificity of direct paired comparisons (DPCs) t o detect changes in absolute myocardial perfusion measured with Rb-82 PET. Methods: Repeated dynamic 82Rb PET scans were obtained on 8 dogs at rest an d during hyperemia induced with dobutamine (n = 4) or atrial pacing (n = 4) . Radiolabeled microspheres were used to verify perfusion changes. Polar ma ps of absolute Rb-82 retention and associated SD were estimated from the dy namic images. Paired comparisons were then performed using a t test on each of the 532 polar map sectors. Rest-rest and stress-stress differences were used to assess specificity and reproducibility, and stress-rest difference s were used to assess sensitivity. Results: Rb-82 retention differences of 20% over baseline were detected with 85%-90% sensitivity and specificity, u sing the optimal DPC probability value and image smoothness. The average 82 Rb retention differences correlated well with microspheres (r = 0.74; P = 0 .001). Reproducibility of the mean retention values was 4.7% +/- 2.1%. As r eproducibility varies, the DPC probability value can be adjusted to maintai n specificity. These ROC results are directly applicable to other image mod alities that produce measurements with similar SEs (3.7% +/- 0.9%). Conclus ion: The developed method of DPCs is sensitive and specific for the detecti on of changes in absolute myocardial perfusion measured with Rb-82 PET.