Magnetization Transfer Imaging Is Unaffected by Decreases in Renal Perfusion in Swine

Area of Science:

• Radiology and Imaging Science
• Nephrology and Urology
• Biomedical Engineering

Background:

• Multiparametric renal MRI, including diffusion-weighted imaging, magnetic resonance elastography, and magnetization transfer imaging (MTI), is crucial for noninvasive renal fibrosis assessment.
• Hemodynamic changes in diseased kidneys can potentially interfere with the accuracy of renal fibrosis measurements.
• MTI directly assesses tissue macromolecular content, suggesting potential insensitivity to hemodynamic fluctuations.

Purpose of the Study:

• To test the hypothesis that MTI is insensitive to renal hemodynamic changes.
• To evaluate the reliability of MTI in assessing renal structural changes under acute graded ischemia in swine kidneys.

Main Methods:

• Seven domestic pigs underwent induced graded renal ischemia via a silicone cuff around the renal artery.
• Multiparametric MRI, including MTI, diffusion-weighted imaging, and magnetic resonance elastography, was performed at various stenosis levels and reperfusion.
• Histology was used to confirm the absence of renal fibrosis.

Main Results:

• Decreased renal perfusion during ischemia correlated with increased R2*, decreased apparent diffusion coefficient (ADC), and increased stiffness.
• Magnetization transfer ratio (MTR) showed no statistically significant changes during graded ischemia.
• Post-reperfusion, R2*, ADC, and stiffness returned to baseline, while cortical MTR showed a slight decrease.

Conclusions:

• Renal MTI is insensitive to decreases in renal perfusion caused by ischemia.
• MTI demonstrates potential as a reliable tool for assessing renal structural changes, independent of hemodynamic status.
• This finding supports the use of MTI for accurate, noninvasive evaluation of renal conditions.