Exploratory Evaluation of Quantitative Rubidium-82 PET Myocardial Perfusion Parameters: Absolute Blood Flow, Flow...

Background/Objectives: Rubidium-82 (⁸²Rb) PET myocardial perfusion imaging (MPI) yields, in a single study, quantitative absolute myocardial blood flow (MBF, mL/min/g), myocardial flow reserve (MFR), and gated left ventricular (LV) function (LVEF, EDV, ESV, SV). These quantitative values depend on the tracer, scanner, kinetic model, software, and underlying population and have been characterised almost exclusively in North American and European cohorts. The Arabian Gulf, where Kuwait has among the highest age-standardised diabetes prevalence worldwide (25.6%), is essentially unstudied, so the distribution and behaviour of these parameters in such a real-world cardiometabolic population are unknown. To evaluate the distribution of the quantitative ⁸²Rb PET parameter set in a real-world Arabian Gulf cohort and, within a small clinically defined normal subgroup, to describe sex- and age-related patterns in absolute MBF, MFR, and LV function. Given the limited size of the normal subgroup, these values are presented as exploratory, hypothesis-generating observations rather than definitive population reference norms. Methods: Retrospective single-centre study of 330 consecutive ⁸²Rb PET/CT studies (analytic cohort n = 292 after exclusion of repeat studies and those with incomplete quantitative output; mean age 63.1 ± 12.1 years) who underwent adenosine-stress ⁸²Rb PET/CT MPI. The clinically defined normal subgroup, normal perfusion (C1), normal global MFR (≥2.0), normal resting LVEF, and no documented cardiac history, comprised 44 patients (25 female, 19 male). Reference values are reported as sex- and age-stratified centiles (5th, 25th, median, 95th percentiles), with the 5th percentile reported for each parameter. Sex differences used Mann-Whitney U with rank-biserial r and Cohen's d (95% CI); age was examined across broad bands. All analyses followed APA 7 standards with Bonferroni correction. Results: In the clinically defined normal subgroup, median global stress MBF was 2.94 mL/min/g (5th percentile 2.03) and median global MFR was 2.72 (5th percentile 2.06); every value satisfied the C1 definition (MFR ≥ 2.0) by construction, so these limits describe the preselected subgroup and cannot independently validate the 2.0 threshold. Women had higher resting MBF than men (median 1.07 vs. 0.90 mL/min/g; p = 0.007), with numerically lower global MFR that did not survive correction for multiple comparisons (2.57 vs. 2.98; p = 0.022); stress MBF did not differ by sex (3.00 vs. 2.91; p = 0.522). LV volumes were smaller in women, while LVEF was similar between sexes. The 5th percentile for stress LVEF was 54% (women) and 53% (men). These absolute-flow reference values are lower than those reported for Western low-risk cohorts (stress MBF ~3.25 mL/min/g; MFR ~3.18), consistent with the higher cardiometabolic burden of this population. Conclusions: In this exploratory single-centre evaluation, quantitative ⁸²Rb PET flow values in a small clinically defined normal Arabian Gulf subgroup were lower than Caucasian-derived values, while sex-related differences in resting flow were evident and age-related differences were numerically consistent with previously reported trends. Because the normal subgroup is small, these findings are hypothesis-generating and require confirmation in larger, prospectively screened cohorts before use as population reference values; they nonetheless indicate that population- and pipeline-specific calibration is needed when quantitative ⁸²Rb thresholds derived elsewhere are applied locally.