Renal MRI

Monday 22 April 2013

Nur Farhayu Omar¹, Eleanor F. Cox¹, Tobias Breidthardt², Iain B. Squire³, Aghogho Odudu⁴, Mohamed Tarek Eldehni⁴, Chris McIntyre⁴, and Susan T. Francis^1
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, f_pD*, renal artery flux and cortical perfusion with eGFR. We find that flow (f_pD*) contributes to the changes in ADC, but structural changes indicated by a change in T₁ are not reflected in D alone.

Luke Xie^1,2, Russell Dibb^1,2, Wei Li³, Chunlei Liu^2,3, and G. Allan Johnson^1,2
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.

Mingshu Yang¹, Min Ji¹, Bin Yang¹, Li Wang¹, Chunmei Xia², Lixia Yang³, Zhongwei Qiao¹, and Ed X. Wu^4
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.

Andreas Pohlmann¹, Karen Arakelyan^1,2, Kathleen Cantow², Jan Hentschel¹, Bert Flemming², Mechthild Ladwig², Erdmann Seeliger², and Thoralf Niendorf^1,3
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.

Yuan-Cheng Wang¹, Shenghong Ju¹, and Gao-Jun Teng^1
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.

Guillaume Duhamel¹, Valentin Prevost¹, Olivier M. Girard¹, Virginie Callot¹, and Patrick J. Cozzone^1
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.

Andreas Pohlmann¹, Jan Hentschel¹, Mandy Fechner², Uwe Hoff², Gordana Bubalo², Karen Arakelyan^1,3, Kathleen Cantow³, Erdmann Seeliger³, Bert Flemming³, Lajos Marko⁴, Helmar Waiczies^1,5, Sonia Waiczies^1,5, Wolf Hagen Schunck⁴, Dominik N. Mueller^4,6, Duska Dragun², and Thoralf Niendorf^1,5
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.

Jan Hentschel¹, Kathleen Cantow², Andreas Pohlmann¹, Karen Arakelyan^1,2, Bert Flemming², Mechthild Ladwig², Erdmann Seeliger², Uwe Hoff³, Pontus B. Persson², and Thoralf Niendorf^1,4
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.

Xiufeng Li¹, Carl Snyder¹, Pierre-Francois Van de Moortele¹, Kamil Ugurbil¹, and Gregory J. Metzger^1
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.

Katja Hueper¹, Marcel Gutberlet¹, Dagmar Hartung¹, Song Rong², Hermann Haller², Martin Meier³, Frank Wacker¹, and Faikah Gueler^2
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.