ISMRM 21st Annual Meeting & Exhibition 20-26 April 2013 Salt Lake City, Utah, USA

Renal MRI
Monday 22 April 2013
Room 155 EF  10:45 - 12:45 Moderators: Andrew B. Rosenkrantz, Shreyas S. Vasanawala

10:45 0022.   
Renal Diffusion and Perfusion in Cardiorenal Syndrome.
Nur Farhayu Omar1, Eleanor F. Cox1, Tobias Breidthardt2, Iain B. Squire3, Aghogho Odudu4, Mohamed Tarek Eldehni4, Chris McIntyre4, and Susan T. Francis1
1Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom, 2Department of Nephrology, University Hospital Basel, Basel, Switzerland, 3Department of Cardiovascular Sciences, University of Leicester, Leicester, Leicestershire, United Kingdom, 4Department of Renal Medicine, Royal Derby Hospital, Derby, Derbyshire, United Kingdom

Diffusion and perfusion in the kidneys are assessed in cardiorenal syndrome (CRS) patients and healthy volunteers in order to determine whether renal dysfunction in CRS is due to changes in tissue structure (fibrosis) or haemodynamic changes. Strong correlations are found between ADC, fpD*, renal artery flux and cortical perfusion with eGFR. We find that flow (fpD*) contributes to the changes in ADC, but structural changes indicated by a change in T1 are not reflected in D alone.

10:57 0023.   
Susceptibility Tensor Imaging of the Renal Tubule
Luke Xie1,2, Russell Dibb1,2, Wei Li3, Chunlei Liu2,3, and G. Allan Johnson1,2
1Department of Biomedical Engineering, Duke University, Durham, North Carolina, United States, 2Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina, United States, 3Brain Imaging Analysis Center, Duke University Medical Center, Durham, North Carolina, United States

We applied susceptibility tensor imaging (STI) to study the complex nephron structure in a mouse kidney. When using DTI, we found that it was only able to track tubules in the inner medulla. STI, on the other hand, was able to overcome this limitation and tracked tubules beyond the inner medulla. The kidney was imaged with 17 orientations using a 3D multi-echo gradient echo sequence at 9.4T. Measures of anisotropy in tortuous and straight segments were consistent with the uriniferous tubule structure determined from microscopy. STI provides a particularly novel contrast mechanism to assess the tubule microstructure and composition.

11:09 0024.   Changes in Intrarenal Oxygenation as Evaluated by BOLD MRI in a Rat Biliary Obstruction Model
Mingshu Yang1, Min Ji1, Bin Yang1, Li Wang1, Chunmei Xia2, Lixia Yang3, Zhongwei Qiao1, and Ed X. Wu4
1Department of Radiology, Children Hospital of Fudan University, Shanghai, China, 2Department of Physiology and Pathophysiology, Fudan University, Shanghai, China,3Department of Radiology, Xuhui Center Hospital, Shanghai, China, 4Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, China

Blood oxygenation level-dependent (BOLD) MRI was shown to allow non-invasive observation of renal oxygenation. Experimental bile duct ligation has been widely used as an animal model to evaluate the renal molecular changes. This study aims to investigate the alteration of R2* in the kidney of rat induced by biliary duct ligation. We observed that the medullary R2* in model group is higher than that in controls, but the difference in cortical R2* was not significant between two groups. Our results implicated that acute biliary obstruction induced by bile duct ligation caused an alteration of renal medullar oxygenation.

11:21 0025.   Effects of an X-Ray Contrast Medium Administration on Renal T2* and T2
Andreas Pohlmann1, Karen Arakelyan1,2, Kathleen Cantow2, Jan Hentschel1, Bert Flemming2, Mechthild Ladwig2, Erdmann Seeliger2, and Thoralf Niendorf1,3
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck Center for Molecular Medicine, Berlin, Germany, 2Institute of Physiology, Center for Cardiovascular Research, Charité, Berlin, Germany, 3Experimental and Clinical Research Center, a cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine, Berlin, Germany

X-ray contrast media (CM) are usually well tolerated, but can cause acute kidney injury (AKI). Medullary hypoxia is pivotal in the pathophysiology of CM-induced AKI. BOLD-MRI is increasingly used to monitor kidney oxygenation. We studied the effects of injecting a CM into the thoracic aorta on renal T2*/T2 in rats. The CM effects were benchmarked against pathophysiologically relevant reversible interventions: brief periods of hypoxia and aortic occlusion. T2*/T2 mappings during hypoxia and aortic occlusion correspond qualitatively with previous data obtained by invasive tissue pO2 measurements. T2* mapping after CM corroborates invasively obtained data and demonstrates that CM affects medullary oxygenation.

11:33 0026.   Evaluation of Nephrotoxicity of Iso- Versus Low-Osmolar Iodine Contrast Media by BOLD and Diffusion-Weighted MR Imaging
Yuan-Cheng Wang1, Shenghong Ju1, and Gao-Jun Teng1
1Zhongda Hospital, Medical School, Southeast University, Nanjing, Jiangsu, China

Arguments on the nephrotoxicity of iodixanol (iso-osmolality) and iopromide (low-osmolality) have not stopped so far. We performed a study to evaluate the diffusion and oxygenation of the two kinds of contrast medias using diffusion-weighted MR imaging (DWI) and blood oxygen level dependent (BOLD) MRI. The results indicate that iodixanol resulted in a more significant decrease of renal diffusion and oxygenation than iopromide did in the setting of mild dehydration on rabbits. This suggests that iodixanol may not be as safe as people used to think and further study is still needed.

11:45 0027.   High Temporal Resolution Mouse Renal Blood Flow (RBF) Imaging with Pseudo-Continuous ASL (PCASL) at Very High Field
Guillaume Duhamel1, Valentin Prevost1, Olivier M. Girard1, Virginie Callot1, and Patrick J. Cozzone1
1CRMBM / CNRS 7339, Aix-Marseille University, Marseille, France

Assessment of the renal microvascular perfusion is a valuable tool for many diseases which have shown to be linked to damage or loss of renal microvessels. ASL had great potential for measuring renal blood flow in humans and animal models. Most of the reported animal studies were performed with the moderately sensitive FAIR EPI technique, moreover limited to transverse imaging only. In this study, we investigated mouse RBF measurements using pseudo-continuous ASL in combination with fast imaging, with the aim of determining the most adapted protocol relative to sensitivity, robustness to motion, reduced scan time, multislice acquisition and imaging orientation.

11:57 0028.   Assessment of Experimental Acute Kidney Injury by Fast Interleaved Monitoring of T2* and T2
Andreas Pohlmann1, Jan Hentschel1, Mandy Fechner2, Uwe Hoff2, Gordana Bubalo2, Karen Arakelyan1,3, Kathleen Cantow3, Erdmann Seeliger3, Bert Flemming3, Lajos Marko4, Helmar Waiczies1,5, Sonia Waiczies1,5, Wolf Hagen Schunck4, Dominik N. Mueller4,6, Duska Dragun2, and Thoralf Niendorf1,5
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck Center for Molecular Medicine, Berlin, Germany, 2Nephrology and Intensive Care Medicine, Center for Cardiovascular Research, Charité, Berlin, Germany, 3Institute of Physiology, Center for Cardiovascular Research, Charité, Berlin, Germany, 4Max Delbrück Center for Molecular Medicine, Berlin, Germany, 5Experimental and Clinical Research Center, a cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine, Berlin, Germany,6Nikolaus-Fiebiger-Center, Friedrich-Alexander-University, Erlangen-Nürnberg, Germany

Acute kidney injury (AKI) is commonly caused by renal hypoperfusion. This ischemia/reperfusion (I/R) injury is characterized by a mismatch of local tissue oxygen supply and demand. There is an unmet need to better understand the mechanisms of the initial phase of I/R injury in AKI. Mapping of T2*/T2, known to be sensitive to blood oxygenation, might elucidate spatio-temporal pathophysiological changes in the kidney. We demonstrate for the first time the feasibility of continuous, high temporal resolution parametric MRI monitoring of renal I/R in rats. Observations in the early reperfusion phase promise to offer new insights into the pathogenesis of AKI.

12:09 0029.   
Combination of Non-Invasive Parametric MRI and Invasive Physiological Measurements: Towards a Hybrid and Integrated Approach for Investigation of Acute Kidney Injury
Jan Hentschel1, Kathleen Cantow2, Andreas Pohlmann1, Karen Arakelyan1,2, Bert Flemming2, Mechthild Ladwig2, Erdmann Seeliger2, Uwe Hoff3, Pontus B. Persson2, and Thoralf Niendorf1,4
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrueck Center for Molecular Medicine, Berlin, Germany, 2Institut für Vegetative Physiologie, Charité Campus Mitte, Berlin, Germany, 3Nephrology and Intensive Care Medicine, Charité – Universitätsmedizin Berlin, Campus Virchow- Klinikum, Berlin, Germany, 4Experimental and Clinical Research Center a joint cooperation between the Charité Medical Faculty, and the Max-Delbrueck Center for Molecular Medicine, Berlin, Germany

Renal medullary hypoperfusion and hypoxia play a pivotal role in acute kidney injury. Invasive but quantitative physiological methods are used for targeted probing of kidney perfusion as well as regional perfusion and oxygenation in animals in vivo. We set out to combine invasive techniques and non-invasive MRI in an integrated hybrid setup with the ultimate goal to monitor and interpret parametric MR and physiological parameters by means of standardized interventions. Our preliminary results demonstrate that simultaneous measurement of tissue pO2, flux, renal blood flow, arterial blood pressure and MRI is feasible.

12:21 0030.   Feasibility of Single Breath-Hold Renal Perfusion Imaging at 7T
Xiufeng Li1, Carl Snyder1, Pierre-Francois Van de Moortele1, Kamil Ugurbil1, and Gregory J. Metzger1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

Due to the intrinsically low signal noise ratio nature of ASL imaging, lengthy signal averaging and correspondingly long imaging acquisition times are usually needed in renal perfusion imaging at lower fields, which not only makes imaging sensitive to physiological motion but also imposes critical limitations on its application in patients. The increased SNR, prolonged longitudinal relaxation times, and better parallel imaging performance of ultra high field provide the potential to reduce imaging acquisition time and motion-associated artifacts. The feasibility of single breath-hold renal ASL perfusion imaging at 7T was evaluated and reported in this abstract.

12:33 0031.   
Arterial Spin Labeling for Quantification and Monitoring of Renal Blood Flow Changes After Acute Kidney Injury in Mice – Comparison with Histopathology and Renal Function
Katja Hueper1, Marcel Gutberlet1, Dagmar Hartung1, Song Rong2, Hermann Haller2, Martin Meier3, Frank Wacker1, and Faikah Gueler2
1Radiology, Hannover Medical School, Hannover, Germany, 2Nephrology, Hannover Medical School, Hannover, Germany, 3Institute of Animal Science, Hannover Medical School, Hannover, Germany

We investigated whether arterial spin labeling (ASL) allows monitoring renal perfusion impairment after acute kidney injury (AKI) in mice. Moderate and severe AKI were induced and renal blood flow (RBF) was measured by ASL using a 7T scanner. At day 7, RBF was significantly reduced after moderate and severe AKI. RBF returned to baseline at d28 after moderate, whereas it remained significantly reduced after severe AKI. RBF-changes correlated with impairment of renal function, renal fibrosis and kidney volume loss. Thus, ASL may help to non-invasively detect renal perfusion impairment and presence and severity of AKI at an early time point.