Multiparametric Renal MRI: An Intrasubject Test-Retest Repeatability Study.

Background: Renal multiparametric magnetic resonance imaging (MRI) is a promising tool for diagnosis, prognosis, and treatment monitoring in kidney disease.
Purpose: To determine intrasubject test-retest repeatability of renal MRI measurements.
Study Type: Prospective.
Population: Nineteen healthy subjects aged over 40 years.
Field Strength/sequences: T ₁ and T ₂ mapping, R ₂ * mapping or blood oxygenation level-dependent (BOLD) MRI, diffusion tensor imaging (DTI), and intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI), 2D phase contrast, arterial spin labelling (ASL), dynamic contrast enhanced (DCE) MRI, and quantitative Dixon for fat quantification at 3T.
Assessment: Subjects were scanned twice with ~1 week between visits. Total scan time was ~1 hour. Postprocessing included motion correction, semiautomated segmentation of cortex and medulla, and fitting of the appropriate signal model.
Statistical Test: To assess the repeatability, a Bland-Altman analysis was performed and coefficients of variation (CoVs), repeatability coefficients, and intraclass correlation coefficients were calculated.
Results: CoVs for relaxometry (T ₁ , T ₂ , R ₂ */BOLD) were below 6.1%, with the lowest CoVs for T ₂ maps and highest for R ₂ */BOLD. CoVs for all diffusion analyses were below 7.2%, except for perfusion fraction (F _P ), with CoVs ranging from 18-24%. The CoV for renal sinus fat volume and percentage were both around 9%. Perfusion measurements were most repeatable with ASL (cortical perfusion only) and 2D phase contrast with CoVs of 10% and 13%, respectively. DCE perfusion had a CoV of 16%, while single kidney glomerular filtration rate (GFR) had a CoV of 13%. Repeatability coefficients (RCs) ranged from 7.7-87% (lowest/highest values for medullary mean diffusivity and cortical F _P , respectively) and intraclass correlation coefficients (ICCs) ranged from -0.01 to 0.98 (lowest/highest values for cortical F _P and renal sinus fat volume, respectively).
Data Conclusion: CoVs of most MRI measures of renal function and structure (with the exception of F _P and perfusion as measured by DCE) were below 13%, which is comparable to standard clinical tests in nephrology.
Level of Evidence: 2 TECHNICAL EFFICACY: Stage 1.
(© 2020 The Authors. Journal of Magnetic Resonance Imaging published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.)