Abstract
Diagnosis of early-stage acute kidney injury (AKI) will benefit from a timely identification of local tissue hypoxia. Renal tissue hypoxia is an early feature in AKI pathophysiology, and renal oxygenation is increasingly being assessed through T2*-weighted magnetic resonance imaging (MRI). However, changes in renal blood volume fraction (BVf) confound renal T2*. The aim of this study was to assess the feasibility of intravascular contrast-enhanced MRI for monitoring renal BVf during physiological interventions that are concomitant with variations in BVf and to explore the possibility of correcting renal T2* for BVf variations. A dose-dependent study of the contrast agent ferumoxytol was performed in rats. BVf was monitored throughout short-term occlusion of the renal vein, which is known to markedly change renal blood partial pressure of O2 and BVf. BVf calculated from MRI measurements was used to estimate oxygen saturation of hemoglobin (SO2). BVf and SO2 were benchmarked against cortical data derived from near-infrared spectroscopy. As estimated from magnetic resonance parametric maps of T2 and T2*, BVf was shown to increase, whereas SO2 was shown to decline during venous occlusion (VO). This observation could be quantitatively reproduced in test–retest scenarios. Changes in BVf and SO2 were in good agreement with data obtained from near-infrared spectroscopy. Our findings provide motivation to advance multiparametric MRI for studying AKIs, with the ultimate goal of translating MRI-based renal BVf mapping into clinical practice en route noninvasive renal magnetic resonance oximetry as a method of assessing AKI and progression to chronic damage.
Highlights
Kidney diseases are a global health burden with steadily increasing incidence [1,2,3,4], leading to an estimated worldwide death toll of 2 million per year from acute kidney injury (AKI) [5,6,7]
Renal tissue hypoxia is an early feature in AKI pathophysiology, and renal oxygenation is increasingly being assessed through T*2-weighted magnetic resonance imaging (MRI)
Features in the pathophysiology of AKI that could lend themselves to detection by noninvasive magnetic resonance (MR) imaging include renal tissue hypoperfusion and hypoxia— factors that are important during the progression from AKI to chronic kidney diseases [16, 19,20,21,22,23,24,25]
Summary
Kidney diseases are a global health burden with steadily increasing incidence [1,2,3,4], leading to an estimated worldwide death toll of 2 million per year from AKI [5,6,7]. A number of biochemical markers are being evaluated for use in diagnosis, risk assessment, and prognosis of AKI, there are currently no specific biomarkers that permit point-of-care diagnosis for early-stage AKI [4, 11, 12]. Strategies under consideration include novel imaging techniques that may be customized to probe early stages of AKI [12, 16,17,18]. Features in the pathophysiology of AKI that could lend themselves to detection by noninvasive magnetic resonance (MR) imaging include renal tissue hypoperfusion and hypoxia— factors that are important during the progression from AKI to chronic kidney diseases [16, 19,20,21,22,23,24,25]. Mapping of renal T2* (or its reciprocal, R2* ϭ 1/T2*) is an established MRI method that is increasingly being used to study kidney disorders [28,29,30]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
