Functional Magnetic Resonance Imaging of the Kidneys-With and Without Gadolinium-Based Contrast

Abstract

Assessment of renal function with magnetic resonance imaging (MRI) has been actively explored in the past decade. In this review, we introduce the principle of MRI and review recent progress of MRI methods (contrast enhanced and noncontrast) in assessing renal function. Contrast-enhanced MRI using ultra-low dose of gadolinium-based agent has been validated for measuring single-kidney glomerular filtration rate and renal plasma flow accurately. For routine functional test, contrast-enhanced MRI may not replace the simple serum-creatinine method. However, for patients with renal diseases, it is often worthy to perform MRI to accurately monitor renal function, particularly for the diseased kidney. As contrast-enhanced MRI is already an established clinical tool for characterizing renal structural abnormalities, including renal mass and ureteral obstruction, it is possible to adapt the clinical MRI protocol to measure single-kidney glomerular filtration rate and renal plasma flow, as demonstrated by recent studies. What makes MRI unique is the promise of its noncontrast methods. These methods include arterial spin labeling for tissue perfusion, blood oxygen-level dependent for blood and tissue oxygenation, and diffusion-weighted imaging for water diffusion. For each method, we reviewed recent findings and summarized challenges.

Keywords: Diffusion coefficient; Glomerular filtration rat; Magnetic resonance imaging; Tissue oxygenation; Tissue perfusion.

Copyright © 2017 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

Figures

Fig. 1

Magnetization relaxation after 90° excitation. A) The x–y component of the magnetization, Mxy, decays exponentially, characterized by spin-spin relaxation time T2. B) The z-component, Mz, is zero immediately after the excitation, and recovers to its pre-excitation state. The recovery process is characterized by spin-lattice relaxation time T1.

Fig. 2

Representative contrast-enhanced images, acquired with 3D spoiled gradient recalled echo sequence. A) A coronal image acquired before contrast injection; B) when the first bolus of contrast reached the renal cortex; C) when contrast reached tubules and collecting ducts; D) when contrast reached renal pelvis.