Renal function measurements from MR renography and a simplified multicompartmental model

Area of Science:

• Nephrology
• Radiology
• Medical Imaging

Background:

• Accurate estimation of single-kidney glomerular filtration rate (GFR) is crucial for diagnosing and managing kidney diseases.
• Current methods for GFR measurement can be invasive or involve radiation exposure.
• Magnetic Resonance (MR) renography offers a non-invasive imaging alternative.

Purpose of the Study:

• To assess the accuracy and identify error sources in single-kidney GFR estimation using low-dose gadolinium-enhanced T1-weighted MR renography.
• To evaluate a three-compartment, six-parameter model for analyzing MR renography data.

Main Methods:

• MR signal intensity curves were converted to concentration-time curves.
• A vascular-nephron system model was applied to aortic, cortical, and medullary enhancement curves.
• Sensitivity and Monte Carlo analyses assessed parameter reliability.
• Comparison with technetium-99m diethylene triamine penta-acetic acid ((99m)Tc-DTPA) clearance and scintigraphy.

Main Results:

• The medullary enhancement curve demonstrated high sensitivity to GFR, with low GFR variability (4%) under simulated noise.
• Bolus dispersion in the aorta had minimal impact on parameter reliability.
• MR renography-derived GFR (4.0-71.4 ml/min) correlated well with (99m)Tc-DTPA measurements (r = 0.84, P < 0.001).
• Bland-Altman analysis showed a mean difference of 11.9 ml/min between methods.

Conclusions:

• A nephron-based multicompartmental model enables clinically useful GFR estimation from low-dose MR renography.
• MR renography provides a reliable and accurate method for assessing single-kidney GFR.
• This technique holds promise for non-invasive renal function assessment.