Renal Function - BOLD
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Wednesday May 11th
Room 511A-C  16:00 - 18:00 Moderators: Hersh Chandarana and Pottumarthi V. Prasad

16:00 438.   Introduction
Diego R. Martin
16:12 439.   Assessment of rhabdomyolysis-induced acute kidney injury (AKI) in mice using Hemodynamic Response Imaging (HRI) 
Zohar Milman1, Jonathan Axelrod1, Samuel Heyman2, Nathalie Corchia1, and Rinat Abramovitch1
1The Goldyne Savad Institute for Gene Therapy, Hadassah Hebrew University Medical Center, Jerusalem, Israel, 2Medicine, Hadassah Hebrew University Medical Center, Jerusalem, Israel

The pathophysiology of rhabdomyolysis-induced AKI is complex and incompletely understood, however hypoxia is one of the factors thought to contribute. The use of MRI for the diagnosis and assessment of AKI is expanding; however, contrast-enhanced studies are limited. We studied the feasibility of HRI, an MRI method, based on BOLD fMRI, combined with hypercapnia and hyperoxia challenges, for monitoring changes in kidney perfusion and hemodynamics during AKI in mice. Our results indicate high correlation between kidney dysfunction and decreased perfusion as measured by HRI. This technique provides supplementary information regarding kidney perfusion, hemodynamics and blood vessels reactivity during evolving AKI.

16:24 440.   Intra-Renal Oxygenation in Radio-contrast Nephropathy Model by BOLD MRI: Effect of the Dose and Viscosity  -permission withheld
Lu-Ping Li1, Tammy Franklin1, Joann Carbray1, Maria Papadopulou-Rosenzweig2, Richard Solomon3, and Pottumarthi V Prasad1
1Radiology / Center for Advanced Imaging, Northshore University Healthsystem, Evanston, IL, United States, 2Radiation Medicine, Northshore University Healthsystem, Evanston, IL, United States, 3Nephrology, University of Vermont, Burlington, VT, United States

Radio-contrast induced nephropathy (CIN) is the 3rd common cause of in-hospital mortality in patients with pre-existing kidney insufficiency. Although iso-osmolal agents are believed to be safer than ionic and high-osmolal agents, the issue remains controversial. Other physical properties such as viscosity may play a significant role in determining risk. Renal hypoxia is known to play a role in the pathophysiology of CIN and BOLD MRI was previously shown to be useful in monitoring the changes in intra-renal oxygenation with iothalamate, an ionic high osmolality agent. Here, we report our preliminary direct comparison between iodixanol, a nonionic iso-osmolal agent and iothalamate.

16:36 441.   Renal BOLD-MRI does not reflect renal function: a prospective study in 368 patients  -permission withheld
Henrik J Michaely1, Linda Metzger1, Ulrike I Attenberger1, Stefan Haneder1, and Stefan O Schoenberg1
1University Medical Center Mannheim, Mannheim, BaWue, Germany

Static BOLD imaging at 1.5T and 3T in a broad patient collective of more than 300 patients did not reveal any correlations between the cortical or medullary R2* value and patients' age or renal function as assessed by the MDRD formula.

16:48 442.   Establishment of a renal oxygen transit model based on BOLD MRI 
Jeff Lei Zhang1, Lizette Warner2, Henry Rusinek1, Hersh Chandarana1, Pippa Storey1, Eric E Sigmund1, Qun Chen1, Lilach O Lerman3, and Vivian S Lee1
1Department of Radiology, New York University, New York, NY, United States, 2MR Development, Methods & Applications Software, Philips Healthcare, Highland Hts, OH, United States, 3Division of Nephrology & Hypertension, Mayo Clinic, Rochester, MN, United States

Renal functional BOLD imaging has shown to be capable of identifying diuretic-induced change in oxygen level in renal medulla. This study proposed an oxygen kinetic model to determine tissue pO2 from BOLD data. Using a subset of experimental BOLD and O2 probe measurements from pig kidneys we first fitted oxygen permeability and regional hematocrit. Using these fitted values, we then tested the performance of the model to predict cortical and medullary pO2 based on BOLD MRI measurements using a different set of experimental data which included direct probe measurements of tissue pO2.

17:00 443.   Measuring whole kidney nephron endowment using MRI 
Scott Charles Beeman1, Min Zhang2, Lina Gubhaju3, David Frakes1,2, John Bertram3, Teresa Wu2, and Kevin Bennett1
1School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona, United States, 2School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona, United States, 3Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia

We have developed and validated robust molecular imaging and image processing techniques that, together, produce an accurate count of individual nephrons. Our technique showed a strong aptitude for isolating nephrons labeled with the cationic form of the superparamagnetic protein ferritin from 3D MRI volumes. The algorithm counted 32,263±2,967 nephrons per kidney in whole kidneys. This compares well to the established histological acid maceration count of 30,585±2,053 per kidney. This work makes it possible to assess whole kidney nephron endowment to study susceptibility to systemic renal diseases in animals and humans.

17:12 444.   Follow-up of Living Kidney Donors After Transplantation by DWI reveals Compensatory Changes in the Remaining Kidney.  -permission withheld
Peter Vermathen1, Tobias Binser1, Harriet C Thoeny2, Chris Boesch1, Felix J Frey3, and Ute Eisenberger3
1Dept. of Clinical Research, University of Bern, Bern, Switzerland, 2Dept. of Radiology, University & Inselspital, Bern, Switzerland, 3Dept. of Nephrology, University & Inselspital, Bern, Switzerland

A prospective longitudinal diffusion weighted imaging (DWI) study was performed in living kidney donors before and after transplantation to examine effects of uninephrectomy in the remaining single kidney. ADC rose significantly in the remaining kidney at day 7 after explantation of the contralateral kidney and remained high three months after transplantation. After one year ADC declined again in cortex, while it remained significantly elevated in medulla. The corticomedullary difference of ADC, which is present pre-transplantation, persisted in the remaining kidney until three months post-transplant and then vanished after 1 year, similar to transplanted kidneys.

17:24 445.   Measurement of Single-Kidney Glomerular Filtration Rate (GFR) by Arterial Spin Labeling 
Xiang He1, and Kyongtae Ty Bae1
1Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States

Single kidney glomerular filtration rate (GFR) is an important clinical measurement of renal function. Conventional radioscintigraphy, CT and MR dynamic contrast-enhanced based imaging techniques require injection of exogenous agents and may not be appropriate for all patients. In this preliminary study, we used the arterial spin labeling (ASL) technique to label blood as an endogenous. Single kidney GFR was estimated from the glomerular water filtration fraction on the basis of the apparent T1ρ difference between the renal corpuscle and cortex parenchyma. The simultaneously measured RBF and GFR are within the range of measurements by other invasive techniques.

17:36 446.   Diffusion Tensor Imaging (DTI) and tractography for assessment of renal allograft dysfunction 
Katja Hueper1, Marcel Gutberlet1, Dagmar Hartung1, Frank Lehner2, Wilfried Gwinner3, Xiaoqi Ding4, and Michael Galanski5
1Radiology, Hannover Medical School, Hannover, Germany, 2General, Abdominal and Transplant Surgery, Hannover Medical School, 3Nephrology, Hannover Medical School,4Neuroradiology, Hannover Medical School, 5Radiology, Hannover Medical School

We investigated whether DTI allows for non-invasive detection of functional and structural changes of renal transplants. 15 kidney transplanted patients with different degrees of allograft dysfunction and 13 healthy volunteers were examined using a fat-saturated echo-planar DTI-sequence (1.5 T MAGNETOM Avanto, 6 diffusion directions, b=0,600 s/mm˛). FA- and ADC-values in the cortex and in the medulla were determined. In transplants FA and ADC were significantly lower in the medulla and in the cortex compared to healthy volunteers. The FA in the medulla correlated with the estimated GFR, thus demonstrating the potential value of DTI in early detecting allograft dysfunction.

17:48 447.   Renal Perfusion Measured Pre- and Post-transplantation with ASL MRI in Donor-Recipient Pairs 
Nathan S Artz1, Elizabeth A Sadowski2, David J Niles1, Karl K Vigen1, Andrew L Wentland1, Arjang Djamali3, Thomas M Grist1,2, and Sean B Fain1,2
1Medical Physics, University of Wisconsin, Madison, WI, United States, 2Radiology, University of Wisconsin, Madison, WI, United States, 3Nephrology, University of Wisconsin, Madison, WI, United States

Monitoring renal function safely and non-invasively is important in prolonging allograft function. This study measured and compared renal perfusion in thirteen donor-recipient (DR) pairs before and after kidney transplantation using a non-contrast, arterial spin labeling (ASL) MR perfusion technique. Mean cortical perfusion decreased from baseline in the donors (pre-transplantation) to 3 months post-transplantation in the recipients (p=0.003), possibly due to loss of function or use of anti-rejection medications in the recipients. There is also a trend of increased perfusion in these kidneys, as well as in the donors’ remaining kidneys, between 3 months and 1 year after transplantation.