Quantification of real-time maximal renal perfusion using dynamic renal imaging.

BACKGROUND: Although the peak value of the renal blood perfusion time-activity curve obtained by renal dynamic imaging (RDI) represents the real-time maximum renal blood perfusion (MAX-RP), it is easily affected by the radioactive activity of the injection and is difficult to quantitatively measure. This study proposes a renal blood perfusion peak ratio (RBPPR) model to eliminate injection dose differences and explore its clinical value in quantitatively evaluating MAX-RP. METHODS: A retrospective analysis was conducted on 151 cases (a total of 205 kidneys) who underwent RDI examination from August 2020 to June 2025. According to the 30% limit of the peak difference rate of renal graph and the normal lower limit value of total glomerular filtration rate (GFR), the participants were divided into a control group and an experimental group (which included: the completely compensated group and the incompletely compensated group). Analysis was conducted of distribution of RBPPR and the differences among groups, its correlation with GFR, and its diagnostic efficacy. RESULTS: RBPPR values were concentrated within each group [standard deviation (SD) ≤1.35%]. RBPPR strongly correlated with each kidney GFR (ekGFR; r=0.778, P<0.001). Across the three groups, both ekGFR (F=94.123, P<0.001) and RBPPR (F=43.336, P<0.001) differed significantly. Compared with the control group (RBPPR 3.67%±0.90%, ekGFR 49.12±9.11 mL/min/1.73 m2), the complete compensation group showed significantly higher RBPPR (5.20%±1.35%, P<0.001) and ekGFR (76.00±17.75, P<0.001), whereas the incomplete compensation group exhibited elevated ekGFR (58.12±8.50, P<0.001) but no significant RBPPR increase (3.92%±0.66%, P=0.145 vs. control). For diagnosing complete renal compensation, the optimal RBPPR threshold was 3.620%, yielding an area under the curve (AUC) of 0.842 [95% confidence interval (CI): 0.782-0.902], sensitivity 91.6%, and specificity 62.0%. CONCLUSIONS: The RBPPR model can stably and quantitatively evaluate MAX-RP with good accuracy. It provides a simple and reliable new quantitative method for evaluating whether renal function can be completely compensated and the assessment of renal reserve function.