Detection of acute renal ischemia in swine using blood oxygen level‐dependent magnetic resonance imaging
ABSTRACT PurposeTo determine the feasibility and sensitivity of blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) to detect acute renal ischemia, using a swine model, and to present the causes of variability and assess techniques that minimize variability introduced during data analysis.Materials and MethodsBOLD MRI was performed in axial and coronal planes of the kidneys of five swine. Color R2* maps were calculated and mean R2* values and 95% confidence intervals (CIs) for the cortex and medulla were determined for baseline, renal artery occlusion and reperfusion conditions. Paired Student's t-tests were used to determine significance.ResultsMean R2* measurements increased from baseline during renal artery occlusion in the cortex (axial, 13.8–24.6 second−1; coronal, 14.4–24.7 second−1) and medulla (axial, 19.3–32.2 second−1; coronal, 20.1–30.7 second−1). These differences were significant for both the cortex (axial, P < 0.04; coronal, P < 0.005) and medulla (axial, P < 0.02; coronal, P < 0.0005). No significant change was observed in the contralateral kidney.ConclusionR2* values were significantly higher than baseline for medulla and cortex during renal artery occlusion. More variability exists in R2* measurements in the medulla than the cortex and in the axial than the coronal plane. J. Magn. Reson. Imaging 2005. © 2005 Wiley-Liss, Inc.
SourceAvailable from: Joel Neugarten[Show abstract] [Hide abstract]
ABSTRACT: Blood oxygen level-dependent magnetic resonance imaging (BOLD MRI) has recently emerged as an important noninvasive technique to assess intrarenal oxygenation under physiologic and pathophysiologic conditions. Although this tool represents a major addition to our armamentarium of methodologies to investigate the role of hypoxia in the pathogenesis of acute kidney injury and progressive chronic kidney disease, numerous technical limitations confound interpretation of data derived from this approach. BOLD MRI has been utilized to assess intrarenal oxygenation in numerous experimental models of kidney disease and in human subjects with diabetic and nondiabetic chronic kidney disease, acute kidney injury, renal allograft rejection, contrast-associated nephropathy, and obstructive uropathy. However, confidence in conclusions based on data derived from BOLD MRI measurements will require continuing advances and technical refinements in the use of this technique.International Journal of Nephrology and Renovascular Disease 01/2014; 7:421-435. DOI:10.2147/IJNRD.S42924
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ABSTRACT: We sought to develop a unique sensor-reporter approach for functional kidney imaging that employs circulating perfluorocarbon nanoparticles and multinuclear (1) H/(19) F MRI. (19) F spin density weighted and T1 weighted images were used to generate quantitative functional mappings of both healthy and ischemia-reperfusion (acute kidney injury) injured mouse kidneys. (1) H blood-oxygenation-level-dependent (BOLD) MRI was also employed as a supplementary approach to facilitate the comprehensive analysis of renal circulation and its pathological changes in acute kidney injury. Heterogeneous blood volume distributions and intrarenal oxygenation gradients were confirmed in healthy kidneys by (19) F MRI. In a mouse model of acute kidney injury, (19) F MRI, in conjunction with blood-oxygenation-level-dependent MRI, sensitively delineated renal vascular damage and recovery. In the cortico-medullary junction region, we observed 25% lower (19) F signal (P < 0.05) and 70% longer (1) H T2* (P < 0.01) in injured kidneys compared with contralateral kidneys at 24 h after initial ischemia-reperfusion injury. We also detected 71% higher (19) F signal (P < 0.01) and 40% lower (1) H T2* (P < 0.05) in the renal medulla region of injured kidneys compared with contralateral uninjured kidneys. Integrated (1) H/(19) F MRI using perfluorocarbon nanoparticles provides a multiparametric readout of regional perfusion defects in acutely injured kidneys. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc.Magnetic Resonance in Medicine 06/2014; 71(6). DOI:10.1002/mrm.24851 · 3.40 Impact Factor
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ABSTRACT: Presence of renal hypoxia and its consequences to renal pathophysiology is well accepted now. Most data on renal oxygenation available today are based on animal models, and an ability to translate the findings to humans was highly desired. Although, several novel methodologies are being pursued, to date blood oxygenation level dependent (BOLD) magnetic resonance imaging (MRI) is the only known technique available to evaluate renal oxygenation in humans. The technique is noninvasive, based on an endogenous contrast mechanism, and can be applied to both animal models and humans. The ability to evaluate relative renal oxygenation status in both health and disease could be useful in better understanding the pathophysiology and allowing for monitoring of potential novel interventions. In this chapter, we provide an overview of the principles involved and the implementation and various applications that investigators around the world have pursued to date.