Intravoxel Incoherent Motion (IVIM) and Diffusion Tensor Imaging (DTI) in Healthy Kidney: Influence of Renal Flow Challenge
Eric Edward Sigmund¹, Pierre Hughes Vivier¹, Nicole Lamparello¹, Dabang Sui¹, Artem Mikheev¹, Henry Rusinek¹, Vivian S. Lee¹, Lei Zhang¹, Hersh Chandarana^1
1Radiology, New York University Langone Medical Center, New York, NY, United States

Renal fluid transport is a superposition of flow, resorption, and diffusion, and diffusion-weighted imaging (DWI) in the kidney is correspondingly complex.  Advanced DWI protocols have emerged, such as intravoxel incoherent motion (IVIM) for flow/diffusion separation, and diffusion tensor imaging (DTI) for measurement of flow or structural anisotropy.  We employed these two approaches in a cohort of  normal volunteers undergoing MRI at baseline and following two flow challenges (hydration and furosemide).  Six diffusion metrics (apparent diffusion coefficient ADC, tissue diffusivity Dt, perfusion fraction fp, pseudodiffusivity Dp, mean diffusivity MD, fractional anisotropy FA) were evaluated for reproducibility, tissue contrast, and challenge response.

Determination of Glomerular Filtration Rate in Cirrhotic Patients by MR Renography: Pilot Study
Pierre-Hugues Vivier^1,2, Pippa Storey¹, Jeff L. Zhang¹, Akira Yamamoto¹, Kristopher Tantillo¹, Ruth P. Lim¹, James S. Babb¹, Henry Rusinek¹, Devon John³, Lewis W. Teperman³, Kent Friedman⁴, Judith Benstein⁵, Edward Skolnik⁵, Vivian S. Lee^1
1Radiology, NYU Langone Medical Center, New York, New-York, United States; ²LITIS Laboratory EA4108, School of Medicine and Pharmacy, Rouen, France; ³Transplant Clinic, NYU Langone Medical Center, New York, New-York, United States; ⁴Nuclear Medicine, NYU Langone Medical Center, New York, New-York, United States; ⁵Nephrology, NYU Langone Medical Center, New York, New-York, United States

Glomerular filtration rate (GFR) assessment based on creatinine formulas is highly inaccurate in cirrhotic patients, despite its utmost importance. We prospectively investigated the feasibility, accuracy, precision and reproducibility of MR-GFR measurements in 20 cirrhotic patients undergoing routine liver MRI, using a protocol that added less than 10 additional minutes and 3 mL gadoteridol. Urinary clearance of 99mTc-DTPA served as reference GFR. MR-GFR values were more accurate and precise than creatinine-based GFR values. Reproducibility was comparable to the reference method.

Accurate and Precise Measurement of Renal Filtration and Vascular Parameters Using DCE-MRI and a 3-Compartment Model
Paul S. Tofts¹, Marica Cutajar^1,2, Iosif Mendichovszky³, Isky Gordon^2
1Imaging Physics, Brighton & Sussex Medical School, Brighton, East Sussex, United Kingdom; ²Radiology and Physics, UCL Institute of Child Health, London, United Kingdom; ³University of Manchester, Manchester, United Kingdom

The precision and accuracy of a recent compartmental model of renal DCE-MRI is investigated. Precision is assessed by repeated examination of 15 normal volunteers; accuracy is assessed by comparison with published values (where available). Local filtration (Ktrans) is reproducible (instrumental sd 15%) and accurate (0.25 min-1), giving GFR 115 mL min-1. Mean Transit Time (5.9 s) is reproducible (sd 6%) and a candidate biomarker. Blood flow is reproducible to 12%, although absolute values are high. Filtration fraction is more reproducible (8%) although lower than published values. Normal kidney volume was measured as 214 mL/1.73m2.

Multiphase True-FISP ASL in the Kidney
Caroline L. Hoad¹, Eleanor F. Cox¹, Alexander G. Gardener¹, Devasuda Anblagan¹, Susan T. Francis^1
1School of Physics and Astronomy, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom

Multiphase True-FISP ASL is implemented in the kidney. This technique provides a robust method to map the transit time, perfusion rate and longitudinal relaxation time of the kidney in a total acquisition time of less than 5 minutes. Maps of these parameters are shown, with transit time maps depicting a clear increase in transit time from feeder vessels to the outer edge of the renal cortex, and perfusion maps displaying significant differences between renal cortex, medulla, and feeder vessels. The mean transit time to the renal cortex was 368±52 ms, mean perfusion rate 246±21 ml/100g/min and mean T₁ 1132±63 ms.

Effect of Iodixanol, a Iso-Osmolar Radio-Contrast Agent on Intra-Renal Oxygenation by BOLD MRI - not available
Lu-Ping Li¹, JoAnn Carbray¹, Maria Papadopulou-Rosenzweig², Richard Solomon³, Pottumarthi V. Prasad^1
1Radiology, Northshore University Healthsystem, Evanston, IL, United States; ²Radiation Medicine, Northshore University Healthsystem, Evanston, IL, United States; ³Nephrology, University of Vermont, Burlington, Burlington, VT, United States

Radiocontrast nephropathy (RCN) is the 3rd common cause of in-hospital mortality in patients with pre-existing kidney insufficiency. Although low- and iso-osmolal radiocontrast are in general believed to be safer than older ionic and high-osmolal agents, the issue remains controversial. Renal hypoxia plays a role in the pathophysiology of RCN and  BOLD MRI was previously shown to be useful in monitoring the changes in intra-renal oxygenation with iothalamate, a 1st generation ionic high osmolality agent.  Here, we report our preliminary findings using iodixanol, a 3rd generation nonionic iso-osmolality agent, that suggest similar trends as reported earlier with iothalamate.

Optimisation of Oxygen-Enhanced Imaging in the Kidney
Katherine Frances Holliday^1,2, Josephine H. Naish^1,2, Jean Tessier³, Geoffrey J M Parker^1,2
1Imaging Sciences, The University of Manchester, Manchester, United Kingdom; ²Biomedical Imaging Institute, Manchester, United Kingdom; ³Early Clinical Development, AstraZeneca, Macclesfield, United Kingdom

In this work we have optimised two sequences commonly used in Oxygen-Enhanced MRI (OE-MRI), Inversion-prepared Half Fourier Turbo Spin Echo (IR-HASTE) and Spoiled Gradient Echo (SPGR), for use in the kidneys. We then compared their abilities in vivo in a single subject. Finally we carried out a dynamic OE-MRI study in the kidneys of a small group of healthy volunteers. We showed that through the parameterisation of the dynamic signal curve obtained during gas switch-over, it is possible to create maps which distinguish between regions in the kidney with differing oxygen delivery.

An Arterial Spin Labeling Approach to Kidney Perfusion:  Assessing Reproducibility in Native and Transplanted Kidneys
Nathan S. Artz¹, Elizabeth A. Sadowski², Andrew L. Wentland¹, Songwon Seo³, Arjang Djamali⁴, Sean B. Fain^1,2
1Medical Physics, University of Wisconsin-Madison, Madison, WI, United States; ²Radiology, University of Wisconsin-Madison, Madison, WI, United States; ³Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, WI, United States; ⁴Nephrology, University of Wisconsin-Madison, Madison, WI, United States

An ASL-FAIR approach was used to measure kidney perfusion in the cortex of 10 native kidneys and 15 transplanted kidneys in subjects with a wide range of kidney function. Exams were repeated within each visit and on two separate days and evaluated for reproducibility. The average within day Interclass Correlation Coefficient (ICC) was 0.93 with a Coefficient of Variation (CV) of 7.6% and the average between day ICC was 0.91 with a CV of 10.6%.  This ASL method is reproducible in the cortex of the kidney. The data also provides guidelines for differentiating normal and abnormal perfusion variation during longitudinal assessment.

Early Detection of Transplant Rejection by In Vivo ¹⁹F MRI
Ulrich Flögel¹, Su Song², Inga Kreideweiß¹, Zhaoping Ding¹, Oliver Witzke², Jürgen Schrader^1
1Institut für Herz- und Kreislaufphysiologie, Heinrich-Heine-Universität, Düsseldorf, NRW, Germany; ²Klinik für Nephrologie, Universitätsklinikum Essen, Germany

This study was aimed at developing an approach for the early in vivo detection of organ rejection in a murine heterotopic abdominal heart transplantation model. As contrast agent emulsified perfluorocarbons (PFCs) were used, which are biochemically inert and are known to be phagocytized by monocytes/macrophages. ¹H/¹⁹F MRI enabled us to detect the initial immune response not later than 3 days after surgery, when conventional parameters did not reveal any signs of rejection. The results show that intravenously applied PFCs accumulate in areas affected by rejection and can be sensitively detected by ¹H/¹⁹F MRI at a field strength of 9.4 T.