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.