Multiparametric Renal Magnetic Resonance Imaging: Validation, Interventions, and Alterations in Chronic Kidney Disease

Background: This paper outlines a multiparametric renal MRI acquisition and analysis protocol to allow non-invasive assessment of hemodynamics (renal artery blood flow and perfusion), oxygenation (BOLD T ₂ ^*), and microstructure (diffusion, T ₁ mapping).

Methods: We use our multiparametric renal MRI protocol to provide (1) a comprehensive set of MRI parameters [renal artery and vein blood flow, perfusion, T ₁, T ₂ ^*, diffusion (ADC, D, D ^*, f _p), and total kidney volume] in a large cohort of healthy participants (127 participants with mean age of 41 ± 19 years) and show the MR field strength (1.5 T vs. 3 T) dependence of T ₁ and T ₂ ^* relaxation times; (2) the repeatability of multiparametric MRI measures in 11 healthy participants; (3) changes in MRI measures in response to hypercapnic and hyperoxic modulations in six healthy participants; and (4) pilot data showing the application of the multiparametric protocol in 11 patients with Chronic Kidney Disease (CKD).

Results: Baseline measures were in-line with literature values, and as expected, T ₁-values were longer at 3 T compared with 1.5 T, with increased T ₁ corticomedullary differentiation at 3 T. Conversely, T ₂ ^* was longer at 1.5 T. Inter-scan coefficients of variation (CoVs) of T ₁ mapping and ADC were very good at <2.9%. Intra class correlations (ICCs) were high for cortex perfusion (0.801), cortex and medulla T ₁ (0.848 and 0.997 using SE-EPI), and renal artery flow (0.844). In response to hypercapnia, a decrease in cortex T ₂ ^* was observed, whilst no significant effect of hyperoxia on T ₂ ^* was found. In CKD patients, renal artery and vein blood flow, and renal perfusion was lower than for healthy participants. Renal cortex and medulla T ₁ was significantly higher in CKD patients compared to healthy participants, with corticomedullary T ₁ differentiation reduced in CKD patients compared to healthy participants. No significant difference was found in renal T ₂ ^*.

Conclusions: Multiparametric MRI is a powerful technique for the assessment of changes in structure, hemodynamics, and oxygenation in a single scan session. This protocol provides the potential to assess the pathophysiological mechanisms in various etiologies of renal disease, and to assess the efficacy of drug treatments.