Intrarenal oxygenation by blood oxygenation level‐dependent MRI in contrast nephropathy model: Effect of the viscosity and dose

Purpose: To compare the effects of osmolality versus viscosity of radio‐contrast media on intra‐renal oxygenation as determined by blood oxygenation level‐dependent (BOLD) MRI in a model of contrast induced nephropathy (CIN). Materials and Methods: Twenty‐four Sprague‐Dawley rats were divided into five groups. Nitric oxide synthase inhibitor L‐NAME (10 mg/kg), cyclooxygenase inhibitor indomethacin (10 mg/kg), or saline, and radio‐contrast iodixanol (high viscosity, 784 or 1600 mg I/kg) or iothalamate (high osmolality, 1600 mg I/kg) were administered. BOLD MRI images were acquired on Siemens 3 Tesla (T) scanner using a multiple gradient recalled echo sequence at baseline, following L‐NAME (or saline), indomethacin (or saline), and radio‐contrast agents. R2* (=1/T2*) was used as the BOLD MRI parameter in renal medulla and cortex. Mixed‐effects models with first order auto‐regressive variance‐covariance models were used to analyze the data. Results: The magnitude of change in medullary R2* (MR2*) with same dose of iodine was larger with iodixanol compared with iothalalmate both in pretreated groups (303% versus 225.6%, < 0.01) and the control group (191.6% versus −1.8%, P < 0.01). The MR2* change in high dose iodixanol was approximately twice compared with the low dose (303% versus 133%, P < 0.01). Conclusion: The viscosity of radio‐contrast seems to play a more significant role than osmolality in terms of renal oxygenation changes as evaluated by BOLD MRI. Additionally, iodixanol induced a dose‐dependent increase in renal medullary hypoxia. J. Magn. Reson. Imaging 2012;36:1162–1167. © 2012 Wiley Periodicals, Inc.