MT-MRI for detection of renal interstitial fibrosis in renovascular disease

We evaluated kidney fibrosis in renovascular disease (RVD) using quantitative (q) and semi-quantitative magnetization-transfer (MT) magnetic resonance imaging (MRI). Ten RVD patients and 22 healthy volunteers (HVs) were prospectively enrolled. Of HVs, 10 (HV-1) underwent imaging studies whereas plasma samples were collected from 12 others (HV-2). The qMT-derived bound-pool fraction (f) was compared to MRI-based MT imaging (MTI)-derived MT ratio (MTR), blood oxygenation-level-dependent (BOLD) R2*, and diffusion-weighted imaging (DWI) apparent diffusion coefficient (ADC). MTR was assessed at offset frequencies of 600 Hz and 1000 Hz, and RVD qMT and MTI on both 1.5T and 3.0T MRI. Additionally, we measured plasma and urinary levels of fibrogenic cytokines and micro-RNAs, and stenotic kidney (STK) perfusion and volume with multidetector computed-tomography (MDCT). At 3.0T-MRI, STK cortex and medulla qMT-f were higher in RVD vs. HV-1 (p = 0.01, p = 0.05, respectively), as was MTR-600 Hz, whereas BOLD-R2* and the DWI ADC were not different. MTR and f measured at 1.5T were comparable to those obtained at 3.0T. STK blood flow was decreased vs. the contralateral kidney (CLK) (p = 0.033) but plasma and urinary fibrogenic indices were unchanged in RVD vs. HV-2. Both f and MTI at 3.0T-MRI may be useful for noninvasive assessment of STK fibrosis, independent of magnetic-field strength. MTI is potentially more sensitive than fibrogenic cytokine levels for detecting mild RVD-related fibrosis changes.