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

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.

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.

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%.

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.