3D PET/CT 82 Rb PET myocardial blood flow quantification: comparison of half-dose and full-dose protocols

Purpose Quantification of myocardial blood flow (MBF) has become central in the clinical application of Rubidium-82 ( 82 Rb) PET myocardial perfusion scans. Current recommendations suggest injections of 1100–1500 MBq of 82 Rb in bolus form, which poses a potential risk of PET system saturation on most 3D PET/CT systems currently being used. We aimed to evaluate the frequency and impact of PET system saturation and to test the potential use of a half-dose acquisition protocol. Methods This study comprised 20 patients who underwent repeated rest scans in a single imaging session, one employing a full-dose (FD), and the other scan a half-dose (HfD) protocol. Datasets were evaluated for saturation based on visual assessments of input functions and sinograms. We compared FD and HfD MBF measurements using Bland–Altman plots, coefficients of variation (CV), and paired t tests. A correction factor permitting serial analyses using FD/HfD imaging protocols was obtained using only the datasets without saturation. Results A dose reduction of 47% was reported for the HfD protocol (FD, 1247 ± 196 MBq; HfD, 662 ± 115 MBq). Saturation effects were observed in 4/20 (20%) FD scans, with none observed in the 20 HfD scans. Assessment of MBFs for FD and HfD protocols revealed bias in the MBF assessments of 0.09 ml/g/min (global MBF, FD = 1.03 ± 0.29 vs HfD = 0.94 ± 0.22 ml/g/min ( p = 0.001)). Exclusion of patients with visually identified saturation effects ( N = 4) reduced the bias to 0.05 ml/g/min (global MBF, FD = 0.97 ± 0.28 vs HfD = 0.92 ± 0.23 ml/g/min ( p = 0.02)). From the datasets without saturation effect, it was possible to generate a bias-correction: Corrected MBF HfD = 1.09*MBF HfD -0.03 ml/g/min. MBF FD and MBF HfD did not differ following the bias correction (MBF FD = 0.97 ± 0.28, MBF HfD,corrected = 0.98 ± 0.25 ml/g/min, p = 0.77). Conclusion Saturation effects can be problematic in 82 Rb MBF studies using the recommended FD protocols for 3D PET/CT scanners. The use of HfD protocol eliminates the risks of saturation and should be used instead of clinical protocols to avoid erroneous results.