Effects of Changes in Analytic Variables and Contrast Material on Measurement of Computed Tomography Glomerular Filtration Rates in Healthy Candidates

Abstract

Purpose This study aimed to prospectively assess the effects of changes in analytic variables and contrast material (CM) osmolality when measuring glomerular filtration rate using computed tomography (CT-GFR). Methods One hundred healthy participants were included in this analysis. Glomerular filtration rate was measured by technetium-99m diethylene-triamine-penta-acetic acid (99mTc-DTPA), and each participant underwent CT-GFR with iodinated CM (iohexol 240 or iobitridol 400) following a crossover study design. Dynamic renal CT scanning was performed. Patlak plot analysis was used to calculate GFR, selecting either the renal cortex or the whole kidney as the region of interest. The renal cortex was analyzed just before time of the second cortical attenuation peak. The whole kidney was analyzed 60, 80, 100, and 120 seconds after the appearance of CM. Automated GFR calculations were performed using perfusion software at 2 noise reduction levels (medium and strong). The CT-GFRs were compared with GFR measured by 99mTc-DTPA. Results There was no significant difference in CT-GFR with iohexol 240 versus iobitridol 400. The CT-GFR at the renal cortex, for the whole kidney 60 seconds after appearance of CM and calculated by perfusion software with medium noise reduction, did not differ significantly from GFR measured by 99mTc-DTPA. Whole-kidney CT-GFR at ≥80 seconds after CM appearance and CT-GFR calculated using perfusion CT software with strong noise reduction were lower when compared with GFR measured by 99mTc-DTPA. Conclusion Results from CT-GFR were most accurate when the kidney cortex was selected as the region of interest or when using 60-second time point for whole-kidney assessment, regardless of CM osmolarity.