Cardiac-Gated Diffusion-Weighted Magnetic Resonance Imaging Assessment of Kidney Function in Patients With Kidney Cancer

Background Estimated glomerular filtration rate (eGFR) from serum creatinine outlines global kidney function, subject to biases in clinical scenarios from muscle wasting and inflammation (prevalent in kidney cancer) and failure to estimate split renal function (crucial in operative planning). Measured GFR (mGFR) (or true mGFRt without body surface area normalization) from 99m Tc-DTPA tracer clearance is the gold standard for bilateral kidney function, involving extended clearance times and radioactivity. Imaging-derived total kidney volumes are functional proxies, but do not probe tissue quality. Methods We employed advanced quantitative diffusion-weighted MRI at 3.0 T in addition to kidney volume measurements in a cohort of 27 renal mass patients (26 and 18 underwent eGFR and mGFR tests, respectively). Cardiac-gated diffusion tensor imaging and intravoxel incoherent motion parameters, were derived. Individual MR metrics were evaluated for correlation with eGFR and mGFR with Pearson correlations and mixed-model analysis, respectively; LASSO-penalized multivariable regression was employed for mGFR prediction. Metrics were compared between proteinuria groups with two-sample t-tests. Results Kidney volume correlated with renal function (split volume vs. split mGFR r=0.54; split volume vs. split mGFRt r=0.69). MR metrics correlated with individual kidney mGFR and mGFRt (r=0.76 and 0.81, respectively). Mixed-effects LASSO multiple regression analysis predicted mGFR and mGFRt (R 2 = 0.880 and 0.700, respectively). MR metrics also differentiated proteinuria status. Discussion Advanced diffusion-weighted MRI metrics may provide surrogates of mGFR and proteinuria. Parameters from bipolar encoding in diastole (emphasizing tubular flow) and flow compensation in systole (emphasizing vascular flow) were often informative.