Magnetic resonance imaging T1- and T2-mapping to assess renal structure and function: a systematic review and statement paper

Abstract

This systematic review, initiated by the European Cooperation in Science and Technology Action Magnetic Resonance Imaging Biomarkers for Chronic Kidney Disease (PARENCHIMA), focuses on potential clinical applications of magnetic resonance imaging in renal non-tumour disease using magnetic resonance relaxometry (MRR), specifically, the measurement of the independent quantitative magnetic resonance relaxation times T1 and T2 at 1.5 and 3Tesla (T), respectively. Healthy subjects show a distinguishable cortico-medullary differentiation (CMD) in T1 and a slight CMD in T2. Increased cortical T1 values, that is, reduced T1 CMD, were reported in acute allograft rejection (AAR) and diminished T1 CMD in chronic allograft rejection. However, ambiguous findings were reported and AAR could not be sufficiently differentiated from acute tubular necrosis and cyclosporine nephrotoxicity. Despite this, one recent quantitative study showed in renal transplants a direct correlation between fibrosis and T1 CMD. Additionally, various renal diseases, including renal transplants, showed a moderate to strong correlation between T1 CMD and renal function. Recent T2 studies observed increased values in renal transplants compared with healthy subjects and in early-stage autosomal dominant polycystic kidney disease (ADPKD), which could improve diagnosis and progression assessment compared with total kidney volume alone in early-stage ADPKD. Renal MRR is suggested to be sensitive to renal perfusion, ischaemia/oxygenation, oedema, fibrosis, hydration and comorbidities, which reduce specificity. Due to the lack of standardization in patient preparation, acquisition protocols and adequate patient selection, no widely accepted reference values are currently available. Therefore this review encourages efforts to optimize and standardize (multi-parametric) protocols to increase specificity and to tap the full potential of renal MRR in future research.

Magnetic resonance fingerprinting for simultaneous renal T1 and T2* mapping in a single breath‐hold

“… map quality was similar to multi‐GRE. times showed larger intersubject variation and medulla MOLLI and MRF values were higher than in the literature …”

“…Chronic kidney disease affects around 10% of the world population and is induced by pathological changes such as inflammation, fibrosis, and edema. These process were shown to increase and, hence, quantitative renal imaging is clinically relevant for detecting a spectrum of pathologies . Changes in oxygen supply can be visualized in the blood oxygenation level‐dependent effect, which correlates with , and has been observed to decrease in CKD and kidney transplants …”

“…The most commonly used method for renal mapping is the modified Look‐Locker inversion recovery (MOLLI), which is based on an inversion recovery pulse followed by several imaging readouts. However, the repeated imaging acquisitions disturb the longitudinal magnetization recovery and compromise acquisition accuracy .…”

MRI in autosomal dominant polycystic kidney disease

“…Characterizing the severity of ADPKD by measuring kidney volumes is tedious, imprecise, and only indirectly measures the disease activity. More functional measures such as renal blood flow, renal parenchymal T 1 and T 2 mapping, multi‐B value DWI including intravoxel incoherent motion analysis, blood oxygen level‐dependent (BOLD) MRI, MR elastography, and dynamic contrast enhancement to assess renal perfusion and fibrotic activity may more directly measure the renal damage allowing for earlier detection of subclinical changes.…”

In vivo demonstration of microscopic anisotropy in the human kidney using multidimensional diffusion MRI

“…In addition to STE, double‐diffusion encoding methods, which encode diffusion along 2 directions before readout, provide planar b ‐tensors that also allow quantification of µFA . Contrast‐agent free quantitative biomarkers are actively being sought‐after in the field of renal MRI . In diffusion tensor imaging (DTI), FA has been widely used in the kidneys as a non‐invasive probe of tubular integrity and the geometric arrangement of microscopic structure.…”