Noninvasive Assessment of Liver Stiffness with Tagged MRI
Sohae Chung¹, Elodie Breton¹, Lorenzo Mannelli¹, Hersh Chandarana¹, Leon Axel^1
1Radiology, NYU Langone Medical Center, New York, NY, United States

A pathological hallmark of the progression to cirrhosis is the development of liver fibrosis, so that monitoring the appearance and progression of liver fibrosis can be used to guide therapy. Fibrosis of the liver is known to result in increased mechanical stiffness, so that the assessment of liver stiffness is a key feature. In this study, we describe a new MRI liver assessment method by using the pulsations of the heart as an intrinsic motion source and by using magnetization-tagged MRI (tMRI) as a noninvasive method to image the motion of the liver for the assessment of liver stiffness.

Magnetic Resonance Elastography: Feasibility of Liver Stiffness Measurements in Healthy Volunteers at 3Tesla
Lorenzo Mannelli¹, Martin J. Graves¹, Peter Beddy¹, Ilse Joubert¹, Andrew N. Priest², David J. Lomas^1
1Radiology, Addenbrooke's Hospital and University of Cambridge, Cambridge, England, United Kingdom; ²Medical Physics, Addenbrooke's Hospital and University of Cambridge, Cambridge, England, United Kingdom

In this study we evaluated liver stiffness in healthy volunteers using magnetic resonance elastography (MRE) at 3T with the same technique that has been successfully applied at 1.5T. This preliminary work demonstrates the feasibility of liver stiffness evaluation at 3T without modification of the approach used at 1.5T.

Influence of Perfusion on Tissue Stiffness Assessed with MR Elastography
Meng Yin¹, Kevin J. Glaser¹, Arunark Kolipaka¹, Lizette Warner², Jayant A. Talwalkar³, Armando Manduca¹, Richard L. Ehman^1
1Department of Radiology, Mayo Clinic, Rochester, MN, United States; ²Division of Nephrology & Hypertension, Mayo Clinic, Rochester, MN, United States; ³Division of Gastroenterology, Mayo Clinic, Rochester, MN, United States

This preliminary investigation provides evidence that MRE-assessed hepatic and renal stiffness in two controlled animal models has a dynamic component that can increase or decrease following a fluctuation in perfusion. The use of MRE to assess changes in tissue mechanics associated with the dynamic perfusion of tissue provides new insights into the natural history and pathophysiology of hepatic and renal diseases and may have significant diagnostic value. Diagnostic and longitudinal MRE studies should take into account potential dynamic perfusion effects as a potential cause of variability.

Automated T2* Estimation with Complex-Signal Based Weighted Least Squares Exponential Fitting
Shreyas S. Vasanawala¹, Huanzhou Yu², Ann Shimakawa², Michael Jeng³, Jean H. Brittain^4
1Department of Radiology, Stanford University, Stanford, CA, United States; ²Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States; ³Department of Pediatrics, Division of Hematology/Oncology, Stanford University, Stanford, CA, United States; ⁴Applied Science Laboratory, GE Healthcare, Madison, WI, United States

Patients who receive chronic red blood cell transfusion therapy are at risk for iron overload if not receiving appropriate iron chelation.  Quantification of iron deposition for therapeutic decision-making is vital.  We aim to evaluate a method of automated T2* mapping with a weighted least squares algorithm in pediatric patients with suspected hepatic iron deposition and to compare it with a conventional T2* mapping method. Twenty three patients ages 5 to 17 years were recruited. Good correlation was obtained between the methods with R2 of 0.97. It is noted that the simple exponential fitting technique likely over-estimates T2* at short T2*.

MRI of Liver Fibrosis by Fibrin-Fibronectin Targeted Contrast Agent
Darwin S. Gao^1,2, Mingqian Tan³, Jerry S. Cheung^1,2, April M. Chow^1,2, Shu Juan Fan^1,2, Kannie W.Y. Chan^1,2, Kwan Man⁴, Zheng-Rong Lu³, Ed X. Wu^1,2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; ²Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; ³Department of Biomedical Engineering, Case Western Reserve University, Cleveland, United States; ⁴Department of Surgery, The University of Hong Kong, Pokfulam, Hong Kong SAR, China

Liver fibrosis, associated with chronic liver injury, including hepatitis and alcohol intoxication, can progress to cirrhosis and hepatocellular carcinoma. It is characterized by an increased amount of extracellular matrix consisting of fibril-forming collagens and matrix glycoconjugates such as fibronectin The fibrin-fibronectin complexes in fibrotic liver, resulted from cross-linkage between fibrin/fibrinogen and fibronectin, may serve as a specific molecular target for contrast-enhanced MRI. Our preliminary results demonstrated that a fibrin-fibronectin targeted Gd contrast agent provided distinct contrast enhancement in fibrotic liver, as compared with a non-targeted Gd contrast agent, in an experimental model.

T2 Relaxation Time as a Surrogate Marker of Liver Fibrosis
Luiz Siqueira¹, Michael Chew¹, Peter F. Hahn¹, Giles Boland¹, Lawrence T. White², Deborah Gervais¹, Peter R. Mueller¹, Alexander R. Guimaraes^2,3
1Radiology, Massachusetts General Hospital/Division of Abdominal Imaging, Boston, MA, United States; ²Radiology, Massachusetts General Hospital/Martinos Center for Biomedical Imaging, Charlestown, MA, United States; ³Radiology, Division of Abdominal Imaging and Interventional Radiology, Boston, MA, United States

83 patients who underwent both liver MRI and liver biopsy for fibrosis staging within a 6 month period, between January 2004 and December 2008 were enrolled in this IRB approved retrospective study.   All biopsies were staged histologically (Ishak classification system (0-6)) and grouped into mild (stage (1-2) n=20), moderate (stage (3-4), n=17), severe (stage (5-6), n=46).   T2 relaxation time of liver parenchyma in patients was calculated by 2 point fit (mild 66.7 +/- 1.9msec; moderate 71.6 +/- 1.7msec; severe 72.4  +/- 1.4msec) with low standard error (~1.9msec), demonstrating statistically significant difference between degrees of mild vs. severe fibrosis (p<0.05).

Assessment of Liver Fibrosis: Comparison of Magnetic Resonance Elastography (MRE) and Diffusion-Weighted Imaging (DWI)
Frank H. Miller¹, Yi Wang², Robert McCarthy, Zongming Chen, Andrew Larson², Laura Sternick, Daniel Ganger, Richard Ehman³, Josh Levitsky, Reed Omary², Laura Merrick², Bradley D. Bolster, Jr⁴, Sven Zuehlsdorff⁴, Saurabh Shah⁴, Paul Nikolaidis², Vahid Yaghmai^2
1Radiology , Northwestern University Feinberg School of Medicine, Chicago, IL, United States; ²Radiology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States; ³Radiology, Mayo Clinic, Rochester, MN, United States; ⁴Siemens Healthcare

We prospectively compared and assessed the discriminatory capabilities of MRE and DWI in detecting and staging hepatic fibrosis in patients with suspected chronic liver diseases using histopathologic analysis as the reference standard. Our study demonstrated that the stiffness values on MRE had a positive linear correlation with degree of liver fibrosis and had greater capability for discriminating stages of fibrosis compared to ADCs on DWI. Furthermore, the absence of fibrosis, mild fibrosis, moderate fibrosis, and late-stage fibrosis (F3-4) can be distinguished from one to another by stiffness values; however, the individual stages of fibrosis could not be differentiated by ADCs.

Non-Invasive Imaging of Diffuse Liver Disease Using Water T2 and Fat Fractions Obtained from a Breath Hold Radial GRASE Method
Maria I. Altbach¹, Christian Graff², Chuang Huang³, V Abraham¹, Scott W. Squire¹, Denise Bruck⁴, K Ray⁴, T Boyer^4
1Radiology, University of Arizona, Tucson, AZ, United States; ²Division of Imaging and Applied Math, U.S. Food and Drug Administration, Silver Spring, MD, United States; ³Mathematics, University of Arizona, Tucson, AZ, United States; ⁴Medicine, University of Arizona, Tucson, AZ, United States

The diagnosis of inflammation, fibrosis, and steatosis is important in the characterization of diffuse liver disease such as Hepatitis C, non-alcoholic steatosis (NASH), and cirrhosis. Currently the diagnosis of these pathologies requires a liver biopsy which is an invasive procedure with associated morbidity and cost. Recently our group developed a novel radial gradient and spin-echo (GRASE) method which provides T2 and fat-water mapping with the advantage that the T2 estimation is independent of the presence of fat. The method is fast (data for T2 and fat-water mapping are acquired in a breath hold) and it provides high spatial resolution and motion insensitivity. In this work we provide the first results in patients with various liver conditions and compare T2 and fat-water information to biopsy results.

Field Strength Reproducibility of Hepatic Proton Density Fat Fraction Estimation  by a Complex-Data, T1-Independent, T2*-Corrected, Spectrum-Modeled MRI Technique
Benjamin Johnson¹, Michael Schroeder¹, Katie Hansen¹, Geraldine HyeWon Kang¹, Tanya Wolfson¹, Anthony Gamst¹, Scott B. Reeder², Claude B. Sirlin¹, Mark Bydder^1
1University of California-San Diego, San Diego, CA, United States; ²University of Wisconsin, Madison, WI, United States

With over ten million Americans affected by non-alcoholic fatty liver disease (NAFLD), there is a need for a non-invasive biomarker of liver fat content.  Because confounders lead to inaccurate estimates of liver fat when using conventional MRI, advanced MRI techniques are being developed and refined to address these problems and accurately and precisely predict hepatic fat content.   We demonstrate the reproducibility across field strength of an advanced complex-based MRI technique that corrects for confounders such as T1 bias, T2*, spectral complexity of liver fat, eddy currents and noise bias.

T1 Independent, T2* Corrected Chemical Shift Based Fat-Water Separation with Accurate Spectral Modeling Is an Accurate and Precise Measure of Liver Fat
Catherine D. G. Hines¹, Alex P. Frydrychowicz^2,3, Dana L. Tudorascu⁴, Gavin Hamilton⁵, Karl K. Vigen², Huanzhou Yu⁶, Charles A. McKenzie⁷, Claude B. Sirlin⁵, Jean H. Brittain⁸, Scott B. Reeder^1,2
1Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States; ²Radiology, University of Wisconsin-Madison, Madison, WI, United States; ³Diagnostic Radiology and Medical Physics, University Hospital Freiburg, Freiburg, Germany; ⁴Waisman Laboratory for Brain Imaging and Behavior, University of Wisconsin-Madison, Madison, WI, United States; ⁵Radiology, University of California-San Diego, San Diego, CA, United States; ⁶Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States; ⁷Medical Biophysics, University of Western Ontario, London, Ontario, Canada; ⁸Applied Science Laboratory, GE Healthcare, Madison, WI, United States

Accurate quantification of hepatic steatosis is essential for early detection of non-alcoholic fatty liver disease, which is increasingly common in Western societies. Quantitative IDEAL provides a means to measure hepatic steatosis in vivo, although its precision and accuracy are unknown.  40 patients were scanned twice using both quantitative IDEAL and MRS to assess accuracy and precision.  Analysis of Bland-Altman plots, concordance correlation coefficients, linear regression and confidence intervals indicate that quantitative IDEAL provides both highly accurate and precise fat-fractions using MRS as a reference and is a reliable method of in vivo fat quantification.