Andreas Pohlmann¹, Karen Arakelyan¹, Till Huelnhagen¹, Kathleen Cantow², Stefanie Kox¹, Yvonne Balke¹, Bert Flemming², Erdmann Seeliger², and Thoralf Niendorf^1,3
1Berlin Ultrahigh Field Facility, Max Delbrueck Center for Molecular Medicine, Berlin, Germany, ²Institute of Physiology and Center for Cardiovascular Research, Charite-Universitaetsmedizin Berlin, Berlin, Germany, ³Experimental and Clinical Research Center, Charite-Universitaetsmedizin Berlin, Berlin, Germany

Acute kidney injuries are often characterized by tissue oxygen hypoxia. T2*-mapping permits probing renal oxygenation but provides a surrogate rather than a quantitative measure of oxygen saturation. The link between tissue pO2 and T2* is influenced by changes in vascular volume fraction. Use of ferumoxytol could permit RBV assessment, which may be essential for unambiguous interpretation of renal T2*. To determine a suitable ferumoxytol dose we combined simulation-based error estimation with in vivo data for doses of 0-10mg Fe/kg during baseline and venous occlusion. Ferumoxytol dose finding was based on the relation of the noise-induced T2*-error to the occlusion-induced T2*-change.

B G Hammond¹, J C Montejano², J M Poth², K M Huber², M Stukova², D Golovko³, and N J Serkova^2
1University of Arizona College of Medicine - Phoenix, Phoenix, Arizona, United States, ²University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States, ³Good Samaritan Medical Center, Massachusetts, United States

Following renal ischemia, reperfusion injuries occur, mediated by a macrophage inflammatory response. Due to the role of macrophages in iron metabolism it is possible to image inflammation using iron oxide nano particles (SPIONs) and T2w-MRI. In this study, acute kidney injury was induced in 10 female C57 mice by clamping the renal artery. Clodronate (CLD) driven macrophage depletion was attempted. In developing this protocol, we have shown that CLD is not an appropriate agent to deplete macrophages in the kidney and that 24hours is not an appropriate time point to assess macrophages using SPION T2-MRI due to their disturbed kinetics.

Andreas Pohlmann¹, Karen Arakelyan^1,2, Dirk Grosenick³, Kathleen Cantow², Heidrun Wabnitz³, Bert Flemming², Rainer Macdonald³, Erdmann Seeliger², and Thoralf Niendorf^1,4
1Berlin Ultrahigh Field Facility, Max Delbrueck Center for Molecular Medicine, Berlin, Germany, ²Institute of Physiology and Center for Cardiovascular Research, Charite-Universitaetsmedizin Berlin, Berlin, Germany, ³Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany, ⁴Experimental and Clinical Research Center, Charite-Universitaetsmedizin Berlin, Berlin, Germany

Renal tissue hypoxia is a key element in the pathophysiology of x-ray contrast media (CM) induced acute kidney injury. T2* mapping permits non-invasive probing of renal oxygenation. There is some discrepancy between reported CM effects on T2* and tissue pO2. Bridging the gap between tissue pO2 measured by invasive physiological methods (PHYSIOL) and T2*, near-infrared spectroscopy (NIRS) provides access to Hb concentration per tissue volume and oxygen saturation of Hb – crucial parameters for interpretation of renal T2*. We studied the effects of intra-arterial injection of iodixanol, a high viscosity x-ray CM, by combining data obtained from MRI, NIRS and PHYSIOL.

Edwin J Baldelomar¹, Jennifer Charlton², and Kevin M. Bennett^3
1Physics, University of Hawaii at Manoa, Honolulu, Hawaii, United States, ²University of Virginia, Virginia, United States, ³Biology, University of Hawaii at Manoa, Hawaii, United States

Here we investigated the use of two MRI contrast agents, cationic ferritin (CF) and gd-DTPA, to measure local macromolecular filtration and glomerular filtration rates in 3D MRI at voxel resolution in isolated, perfused rat kidneys under physiological conditions. CF is a glomerulus-specific, superparamagentic targeted nanoparticle (*ref), and gd-DTPA is eliminated through the tubule. CF uptake rate was thus measured dynamically as a marker for macromolecular filtration, and Gd-DTPA passage was used as a marker for local (voxel) glomerular filtration.

Luke Xie¹, Russell Dibb^1,2, Susan B. Gurley³, Chunlei Liu^1,4, and G. Allan Johnson^1,2
1Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina, United States, ²Biomedical Engineering, Duke University, Durham, North Carolina, United States, ³Division of Nephrology, Department of Medicine, Duke University and Durham VA Medical Centers, Durham, North Carolina, United States, ⁴Brain Imaging Analysis Center, Duke University Medical Center, Durham, North Carolina, United States

In normal kidneys, DTI and susceptibility tensor imaging (STI) can detect and track tubules in the inner medulla. We investigated whether STI can be more sensitive than DTI in models of renal nephropathy (angiotensin receptor knockout and diabetic nephropathy). We found that DTI fractional anisotropy and tractography exhibited some changes in the inner medulla of diseased kidneys. STI, on the other hand, had significantly reduced anisotropy and virtually did not track any tubules in the inner medulla. STI therefore was more sensitive to injury in renal tubules.

Glen Morrell¹, Josh Kaggie¹, and Vivian S. Lee^1
1Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, United States

BOLD MRI has the potential to depict renal hypoxia, but published data are contradictory, likely secondary to limitations in the underlying MRI technique. We have successfully applied 2-dimensional volume selective excitation to reduce the scan time required for full 3D high-resolution renal BOLD imaging of a single kidney to just over 1.5 minutes. This clinically realistic scan time opens the door for the wider investigation of renal BOLD MRI and its ultimate application to assessment of chronic kidney disease progression and response to therapy.

Christopher C. Conlin¹, Jeff L. Zhang^1,2, Florian Rousset^3,4, Clement Vachet³, Yangyang Zhao⁵, Daniel Kim¹, Glen Morrell^1,2, Kathryn A. Morton², Guido Gerig³, and Vivian S. Lee^1,2
1Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, United States, ²Department of Radiology, University of Utah School of Medicine, Salt Lake City, Utah, United States, ³Scientific Computing and Imaging Institute, Salt Lake City, Utah, United States, ⁴CPE Lyon, Lyon, France,⁵Department of Bioengineering, University of Utah, Salt Lake City, Utah, United States

Free-breathing dynamic scans are required to measure renal function with MR renography. These scans suffer from respiratory motion artifacts that must be corrected to accurately estimate functional parameters such as GFR. In this study, we evaluated the efficiency and inter-reader variability of a freely-available image analysis tool that uses the generalized Hough transform to correct respiratory motion artifacts in dynamic renographic scans. We found that the Hough-transform technique is faster and more robust than a previously reported algorithm and leads to more accurate estimates of renal function.

Bastien Milani^1,2, Maciej Piskunowicz^1,3, Isabelle Bassi¹, Christiane Anex¹, Bruno Vogt^1,4, Matthias Stuber^2,5, Michel Burnier¹, and Menno Pruijm^1
1Department of Nephrology and Hypertension, CHUV, Lausanne, Switzerland, ²Center for Biomedical Imaging (CIBM), Lausanne, Switzerland, ³Department of Radiology, Medical University of Gdansk, Gdansk, Poland, ⁴Department of Nephrology and Hypertension, Bern University Hospital, Bern, Switzerland,⁵Department of Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland

Blood oxygenation level dependent MRI (BOLD MRI) is a mapping of R2* which is inversely correlated to the concentration of blood haemoglobin. This abstract presents two items: a new method for the post-processing of renal BOLD MRI and an analysis of a clinical study on the response of the R2* map to the diuretic furosemide using our new post-processing method. This method is based on the “radial R2* distribution”, which accounts for kidney’s anatomy and gives information on the spatial distribution of the R2* map in the cortex and medulla without using arbitrarily defined and operator-dependent regions of interest.

Nan Jiang¹, General Leung^2,3, Serge Jothy⁴, Darren A. Yuen^3,5, and Anish Kirpalani^2,3
1Faculty of Medicine, University of Toronto, Toronto, ON, Canada, ²Department of Medical Imaging, St. Michael's Hospital, University of Toronto, Toronto, ON, Canada, ³Keenan Research Centre, St. Michael's Hospital, Toronto, ON, Canada, ⁴Department of Pathology, St. Michael's Hospital, Toronto, ON, Canada,⁵Division of Nephrology, St. Michael's Hospital, Toronto, ON, Canada

Chronic allograft injury (CAI) is a devastating outcome affecting 60% of kidney transplant patients at 10 years. Fibrosis is the common pathway leading to CAI. We compared stiffness values measured by MR elastography (MRE) in renal allografts to fibrosis measured by biopsy, In our pilot study of 8 patients, we found significant increase in MRE-derived stiffness in allografts with severe fibrosis compared to no, minimal, mild fibrosis and moderate fibrosis. MRE may enable non-invasive quantitative assessment of renal allograft fibrosis and may be able to predict sites for targeted biopsy.

Stanislas Rapacchi^1,2, Robert X Smith³, Yi Wang³, Lirong Yan³, Victor Sigalov⁴, Elizabeth Hernandez⁵, Ajay Verma⁶, Nicolas Wisniacki⁷, Jaime Torrington⁶, Xiang He⁸, Peng Hu⁴, George Karpouzas⁵, Ping-Chun Chiao⁶, and Danny JJ Wang^3
1CRMBM, Aix-Marseille University, Marseille, France, ²Radiology, UCLA, Los Angeles, CA, United States, ³Neurology, UCLA, California, United States, ⁴Radiology, UCLA, California, United States, ⁵Rheumatology, Harbor-UCLA Medical Center, California, United States, ⁶Biogen Idec, Cambridge, MA, United States, ⁷Biogen Idec, MA, United States, ⁸University of Pittsburg, PA, United States

This study evaluates the test-retest repeatability and the sensitivity of a multi-modality renal functional MRI protocol including diffusion weighted imaging (DWI), blood oxygen level dependent (BOLD), T1rho MRI and arterial spin labeling (ASL) in a cohort of healthy subjects (NC) and lupus nephritis (LN) patients.