Abstract
ObjectivesTo validate and adapt a modified two-compartment model, originally developed for magnetic resonance imaging, for measuring human single-kidney glomerular filtration rate (GFR) and perfusion using dynamic contrast-enhanced computed tomography (DCE-CT).MethodsThis prospective study was approved by the institutional review board, and written informed consent was obtained from all patients. Thirty-eight patients with essential hypertension (EH, n = 13) or atherosclerotic renal artery stenosis (ARAS, n = 25) underwent renal DCE-CT for GFR and perfusion measurement using a modified two-compartment model. Iothalamate clearance was used to measure reference total GFR, which was apportioned into single-kidney GFR by renal blood flow. Renal perfusion was also calculated using a conventional deconvolution algorithm. Validation of GFR and perfusion and inter-observer reproducibility, were conducted by using the Pearson correlation and Bland-Altman analysis.ResultsBoth the two-compartment model and iothalamate clearance detected in ARAS patients lower GFR in the stenotic compared to the contralateral and EH kidneys. GFRs measured by DCE-CT and iothalamate clearance showed a close match (r = 0.94, P<0.001, and mean difference 2.5±12.2mL/min). Inter-observer bias and variation in model-derived GFR (r = 0.97, P<0.001; mean difference, 0.3±7.7mL/min) were minimal. Renal perfusion by deconvolution agreed well with that by the compartment model when the blood transit delay from abdominal aorta to kidney was negligible.ConclusionThe proposed two-compartment model faithfully depicts contrast dynamics using DCE-CT and may provide a reliable tool for measuring human single-kidney GFR and perfusion.
Highlights
Glomerular filtration rate (GFR) is a fundamental index of kidney function
Both the two-compartment model and iothalamate clearance detected in ARAS patients lower GFR in the stenotic compared to the contralateral and EH kidneys
GFRs measured by Dynamic contrastenhanced computed tomography (DCE-CT) and iothalamate clearance showed a close match (r = 0.94, P
Summary
Glomerular filtration rate (GFR) is a fundamental index of kidney function. Serum clearance of endogenous or exogenous markers is typically used to estimate GFR [1], but cannot be used to evaluate single-kidney function, which is important to assess in asymmetric renal diseases, such as renal artery stenosis, ureteral obstruction, or renal tumors. Dynamic contrastenhanced computed tomography (DCE-CT) and magnetic resonance imaging (DCE-MRI) have emerged as useful tools for measuring single-kidney GFR as well as renal perfusion. Different methods have been proposed for GFR measurement from DCE-CT, including the Patlak method [2] and its derivatives [3,4,5,6]. This method is only valid when the fitting encompasses data after the vascular peak and before contrast outflow from the selected region of interest (ROI) [5,7]. Application of robust models could facilitate acquisition of DCE-CT-derived functional data
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