Influence of [99mTc]Tc-DTPA extravasation on Gates GFR and the effect of antecubital ROI-based dose correction in renal dynamic scintigraphy.

BACKGROUND: Accurate measurement of the glomerular filtration rate (GFR) is essential for the assessment of kidney function and staging of chronic kidney disease (CKD). Renal scintigraphy using technetium-99m diethylenetriamine pentaacetic acid ([99mTc]Tc-DTPA) is widely used for camera-based GFR estimation. However, extravasation of the radiotracer at the injection site may reduce the systemic dose and underestimate GFR. This study evaluated the impact of [99mTc]Tc-DTPA extravasation on GFR estimation and antecubital fossa count-based dose correction on Gates-derived GFR. MATERIAL AND METHODS: An observational cohort study of 50 patients undergoing [99mTc]Tc-DTPA renal scintigraphy assessed injection-site extravasation using antecubital fossa static imaging. GFR was calculated using the Gates method with and without antecubital count-based dose correction. Paired t-tests were used to compare corrected and uncorrected GFR values. Agreement between the two measurements was evaluated using Bland-Altman analysis. Clinical reclassification at the GFR threshold of 60 mL/min was assessed using McNemar's test. RESULTS: The mean corrected GFR was 61.56 ± 19.16 mL/min, compared to 58.98 ± 19.16 mL/min for the uncorrected GFR, demonstrating a statistically significant mean difference of 2.58 mL/min (p < 0.0001; Cohen's dz = 2.07). Bland-Altman analysis showed a mean bias of 2.58 mL/min, and the estimated GFR progressively decreased, with increasing severity of radiotracer extravasation. CONCLUSIONS: Injection-site extravasation results in systematic underestimation of Gates-derived GFR. Antecubital count-based dose correction increases the estimated GFR and may influence clinical interpretation in borderline cases. Routine assessment of injection-site extravasation may improve the accuracy and reliability of camera-based GFR estimation in renal scintigraphy.