Table 1.

Summary of novel magnetic resonance imaging modalities and their ability to image renal fibrosis

Imaging TechniqueAcronymTargetsStrengthsLimitationsPreclinical studiesHuman Studies
Diffusion-weighted imaging-magnetic resonance imaging and diffusion tensor imagingDWI-MRI (and DTI)Water mobility (ADCtotal)Microvascular perfusion (ADCperfusion)Random water diffusion (ADCdiffusion)Kidney microstructural organization (FA)NoninvasiveMeasures both kidneys entirelyCan estimate microvascular blood flow and overall microstructural integrity of kidneyOther factors besides fibrosis will affect water mobility (e.g., intravascular volume, urine flow rate, edema, medications)↓ kidney ADCtotal (a measure of overall water mobility) in mice subjected to unilateral ureteral obstruction (10) and after allogeneic kidney transplantation (models of fibrosis) (21)
↓ kidney ADCperfusion in mice after unilateral ureteral obstruction (10)
↓ FA in streptozotocin-diabetic uninephrephrectomized mice (18)
↓ water mobility (as measured by ADCtotal): in patients with CKD (1317) and with worsening fibrosis (13,15,21)
↓ microvascular perfusion (as measured by ADCperfusion) in patients with CKD (17)
Arterial spin labelingASLRenal microvascular perfusion (as measured by ASL perfusion score)NoninvasiveMeasures both kidneys entirelyValidated against gold-standard microvascular perfusion measurementsNot able to measure medullary blood flow wellOther factors besides fibrosis will affect microvascular perfusion (e.g., intravascular volume, medications)↓ kidney ASL perfusion score in mice subjected to severe ischemia-reperfusion injury (31)↓ cortical ASL perfusion score in patients with CKD (2830)
Blood oxygenation leveldependent magnetic resonance imagingBOLD MRIBlood oxygenation (as measured by T2*)NoninvasiveMeasures both kidneys entirelyReasonable correlation between T2* and direct tissue pO2 measurementsCannot distinguish between injury that impairs O2 delivery (perfusion) and O2 consumptionOther factors besides fibrosis will affect oxygenation (e.g., intravascular volume, medications, tubular dysfunction)Limited and conflicting data on effects of chronic renal artery stenosis on basal renal oxygenation (as measured by T2*) in mice (37) and rats (42)Basal renal oxygenation (as measured by T2*) is likely unchanged (3841) or ↑ (4345) in CKDWith a furosemide challenge, medullary renal oxygenation ↑ in young, healthy adults, but not in patients with chronic renal injury (40,43,47)
Magnetic resonance elastographyMREKidney stiffeningNoninvasiveMeasures both kidneys entirelyValidated as a measure of fibrosis in the liverKidney stiffness can be influenced by other factors besides fibrosis (e.g., renal blood flow, hydronephrosis, edema)↑ kidney stiffness in rats with nephrocalcinosis-induced renal fibrosis (54)
↑ medullary stiffness in pigs with renal artery stenosis–induced fibrosis (56)
↑ kidney stiffness in renal allografts with moderate (versus mild) fibrosis (53)
  • ADC, apparent diffusion coefficient; FA, fractional anisotropy; ↓, decreased; T2*, the observed transverse relaxation time, which takes into account magnetic field inhomogeneity/susceptibility and is shorter than the inherent T2 of tissue; O2, oxygen; ↑, increased.