Detection of acute renal ischemia in swine using blood oxygen level-dependent magnetic resonance imaging

Purpose: To determine the feasibility and sensitivity of blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) to detect acute renal ischemia, using a swine model, and to present the causes of variability and assess techniques that minimize variability introduced during data analysis. Materials and Methods: BOLD MRI was performed in axial and coronal planes of the kidneys of five swine. Color R2* maps were calculated and mean R2* values and 95% confidence intervals (CIs) for the cortex and medulla were determined for baseline, renal artery occlusion and reperfusion conditions. Paired Student's t-tests were used to determine significance. Results: Mean R2* measurements increased from baseline during renal artery occlusion in the cortex (axial, 13.8-24.6 second(-1); coronal, 14.4-24.7 second(-1)) and medulla (axial, 19.3-32.2 second(-1): coronal, 20.1-30.7 second(-1)). These differences were significant for both the cortex (axial, P < 0.04; coronal, P < 0.005) and medulla (axial, P < 0.02; coronal, P < 0.0005). No significant change was observed in the contralateral kidney. Conclusion: R2* values were significantly higher than baseline for medulla and cortex during renal artery occlusion. More variability exists in R2* measurements in the medulla than the cortex and in the axial than the coronal plane.