Comparison of Planar and 3-Dimensional Methods for Quantification of Differential Renal Function Using ^99m Tc-DMSA and ^99m Tc-Glucoheptonate Renal Scintigraphy

This study aims to determine whether the calculation of the differential renal function (DRF) for renal scintigraphy using volumetric assessment is equivalent to conventional planar assessment using the geometric mean. <b>Methods:</b> A retrospective study was conducted with 108 patients referred for cortical renal scintigraphy. Forty-five patients were injected with ^99mTc-dimercaptosuccinic acid (DMSA), and 63 patients were injected with ^99mTc-glucoheptonate and furosemide, depending on which radiotracer was available at the time of the examination. DRF was measured using automatic 3-dimensional volume-of-interest delineation software on SPECT and 2-dimensional manual regions of interest on planar images, with geometric mean calculated for all patients. Images were reviewed by 2 independent masked observers. To assess intrarater reliability, a random sample of 20 images (10 with ^99mTc-DMSA and 10 with ^99mTc-glucoheptonate) was reprocessed by the same observers to after a minimum 2-wk interval to minimize recall bias. Values obtained by planar and SPECT methods were compared using a paired Student <i>t</i> test. Reproducibility was assessed through intraobserver and interobserver analyses using the intraclass correlation coefficient. <b>Results:</b> There was a significant difference in DRF values obtained by planar and SPECT methods with both ^99mTc-glucoheptonate and ^99mTc-DMSA (<i>P</i> < 0.05), with maximum absolute differences of 40.0% and 13.0%, respectively. High intrarater and interrater intraclass correlation coefficients were obtained for both methods and radiotracers (>0.9), indicating excellent reliability. <b>Conclusion:</b> The SPECT quantification method for the evaluation of DRF is reliable because of high intraobserver and interobserver agreement. Furthermore, it differs significantly from the planar quantification method, with more pronounced differences observed with ^99mTc-glucoheptonate compared with ^99mTc-DMSA.