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Detection of acute renal ischemia in swine using blood oxygen level-dependent magnetic resonance imaging
Sara K Alford1, Elizabeth A Sadowski, Orhan Unal
1Department of Biomedical Engineering, University of Wisconsin-Madison, 53792-3252, USA.
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.
Insights
Blood oxygen level-dependent (BOLD) MRI is feasible for detecting acute kidney injury. R2* values increased significantly during renal artery occlusion, indicating kidney damage.
Area of Science:
- Medical Imaging
- Renal Physiology
- Biomedical Engineering
Background:
- Acute kidney injury (AKI) poses significant clinical challenges.
- Non-invasive imaging techniques are crucial for early AKI detection.
- Blood oxygen level-dependent (BOLD) MRI offers potential for assessing tissue oxygenation.
Purpose of the Study:
- To evaluate the feasibility and sensitivity of BOLD MRI in detecting acute renal ischemia.
- To identify sources of variability in BOLD MRI measurements during renal ischemia.
- To assess methods for minimizing data analysis variability in BOLD MRI.
Main Methods:
- BOLD MRI was performed on five swine, acquiring data in axial and coronal planes.
- Color R2* maps were generated to quantify renal cortex and medulla oxygenation.
- Paired Student's t-tests analyzed changes in R2* values during baseline, occlusion, and reperfusion.
Main Results:
- Mean R2* values significantly increased in both renal cortex and medulla during artery occlusion compared to baseline.
- Significant increases in R2* were observed in both axial and coronal planes (P < 0.04).
- No significant changes were noted in the contralateral, unoccluded kidney.
Conclusions:
- BOLD MRI effectively detects changes in renal oxygenation during acute ischemia.
- R2* measurements showed higher variability in the medulla and axial plane.
- Further optimization of BOLD MRI techniques may enhance its diagnostic utility for AKI.
