Normal and transplanted rat kidneys: diffusion MR imaging at 7 T.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Renal Physiology
• Transplantation Immunology

Background:

• Apparent diffusion coefficient (ADC) mapping provides insights into tissue microstructure and water diffusion.
• Assessing renal blood flow and monitoring kidney transplant rejection non-invasively are critical clinical challenges.

Purpose of the Study:

• To assess the feasibility of reproducible renal ADC map generation in rats using respiratory-triggered spin-echo diffusion-weighted MRI.
• To evaluate the sensitivity of ADC maps for assessing renal blood flow.
• To explore the utility of ADC mapping for monitoring acute rejection in transplanted rat kidneys.

Main Methods:

• Spin-echo diffusion-weighted MRI at 7 Tesla was performed on normal and transplanted rats.
• Angiotensin II infusion was used to induce changes in renal blood flow in normal rats.
• Transplanted kidneys were monitored postoperatively using diffusion-weighted and gradient-echo MRI.

Main Results:

• Reproducible renal ADC maps were obtained, with minor variations between cortex and medulla, and directional differences.
• ADC values significantly decreased (>35%) with reduced renal blood flow induced by angiotensin II.
• Allografts showed significantly decreased ADC values, while isografts had similar ADC values compared to native kidneys.

Conclusions:

• Respiratory-triggered spin-echo diffusion-weighted MRI at 7 Tesla enables reproducible renal ADC map generation in rats.
• ADC mapping demonstrates potential as a noninvasive method for early detection of kidney graft rejection.