Room 355 BC

16:00 - 18:00

Moderators:

Ronald A. Meyer, S. Sendhil Velan

Hanne Hakkarainen¹, Galina Dragneva¹, Petra Korpisalo-Pirinen¹, Seppo Ylä-Herttuala¹, Olli Gröhn², and Timo Liimatainen^1
1A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland, ²University of Eastern Finland, Kuopio, Finland

T₂ and rotating frame relaxation time constants were applied to estimate ischemic muscle viability in a mouse hind limb ischemia model with and without AdhVEGF-D gene therapy. On ischemic leg, percentages of pixels where relaxation times were at the same range as in intact leg were determined and correlated with normal areas determined from histology. High correlations were found with the relaxation times studied (T₂, T₁, T_RAFF2), indicating that they could be used to evaluate ischemic muscle state non-invasively and provide potential imaging marker for therapy outcome.

Khan Hekmatyar¹, Steven J. Foltz², Marisa J. Fortunato², and Aaron M. Beedle^2
1BioImaging Research Center/Complex Carbohydrate Research Center, University of Georgia, Athens, GA, United States, ²Department of Pharmaceutical and Biomedical Sciences, University of Georgia College of Pharmacy, Athens, GA, United States

Quantitative T₂ measured in our dystrophic mouse model has shown distinct dystrophic pathology that correlates with histological measurements at young, but not older ages. Here we explored the role of regenerating muscle fibers in altering T₂ measurements in muscle and sought to identify other parameters to provide complimentary information about the cascade of events occurring after muscle damage. We find that DTI and fiber tracking is a promising means to evaluate muscle fiber regeneration and dystrophic pathology.

Xingui Peng¹, Shenghong Ju¹, Judy Rose James², and Darya P. Shlapak^2
1Jiangsu Key Laboratory of Molecular and Functional Imaging, Department of Radiology, Zhongda Hospital, Medical School, Southeast University, Nanjing, Jiangsu Province, China, ²Department of Radiology, University of Mississippi Medical Center, Jackson, Mississippi, United States

This study aimed to use the diffusion tensor imaging (DTI) and T2 weighted MR imaging to assess the therapeutic effect of endothelia progenitor cell in a mouse model of hind limb ischemia. DTI can be used as a marker in vivo and as a diagnostic tool for assessment of ischemia-induced muscle damage and repair.

Prodromos Parasoglou¹, Ding Xia¹, Gregory Chang¹, Antonio Convit², and Ravinder R. Regatte^1
1Department of Radiology, New York University Langone Medical Center, New York, New York, United States, ²Departments of Psychiatry and Medicine, New York University Langone Medical Center, New York, New York, United States

In this study, we developed and implemented a novel three-dimensional 31P-MT imaging sequence that maps the kinetics of CK in the entire volume of the lower leg within acquisition times that can be tolerated by patients. We tested the sequence on five healthy and two clinically diagnosed type 2-diabetic patients. Overall, we obtained measurements that are in close agreement with measurements reported previously using spectroscopic methods. Importantly, our spatially-resolved method allowed us, in the case of diabetic patients, to detect variations of the CK rate of different calf muscles, which would not have been possible using unlocalized MRS methods.

Donghoon Lee¹, Shu Feng¹, Daniel Chen¹, and Martin Kushmerick^1
1University of Washington, Seattle, WA, United States

We analyzed the time course of changes in mouse hind-limb musculature following localized myotoxin injection by T1, T2, magnetization transfer (MT) and diffusion MRI. Diffusivity and edema increased within the first hours after toxin injection, and faster than the rates of rise of both T2 and MT ratio. Volume decreased faster than T2 and ADC during regeneration. MT returned to control the slowest. Histological analyses confirmed the underlying cellular changes. The kinetics of change in the MRI modalities can be distinguished during muscle damage and regeneration and provide a basis for specific MRI methods to distinguish the underlying cellular processes.

Peng Cao^1,2, Anna M. Wang^1,2, Victor B. Xie^1,2, Shu-Juan J. Fan^1,2, Zhongwei Qiao³, and Ed X. Wu^1,2
1The University of Hong Kong, Hong Kong, Hong Kong SAR, China, ²Department of Electrical and Electronic Engineering, Hong Kong, Hong Kong SAR, China,³Department of Radiology, Fudan University, Shanghai, Shanghai, China

Intramyocellular lipid (IMCL) serves as the principal reservoir for storing cellular energy in muscles. Mounting evidence indicates that elevated IMCL in skeletal muscle is closely associated with insulin resistance and type 2 diabetes. Our experimental results demonstrated that in vivo IMCL ADC can differentiate high fat diet induced obesity and STZ induced diabetes. In diabetic model, IMCL level increased but exhibited more restricted diffusion. In obesity model, the IMCL level increased but the droplet size didn¡¯t change. Diffusion measurements were largely in agreement with our histological observation. Such an MR approach may provide a new dimension in the study of intracellular lipogenesis and lipolysis, and lead to improved understanding and diagnosis in treatment and management of several prevalent metabolic disorders such as obesity and diabetes in both basic and clinical sciences.

Jie Zheng¹, Mary K. Hasting¹, Xiaodong Zhang², Andrew Coggan³, Hongyu An⁴, David Muccigrosso³, Darrah Snozek³, Adil Bashir³, Robert J. Gropler³, and Michael Mueller^5
1Washington University in St. Louis, Saint Louis, Missouri, United States, ²Peking University First Hospital, Beijing, Beijing, China, ³Washington University in St. Louis, Saint Louis, MO, United States, ⁴University of North Carolina, Chapel Hill, NC, United States, ⁵Physical Therapy, Washington University in St. Louis, Saint Louis, MO, United States

A newly developed non-contrast MRI oximetry method was applied to evaluate skeletal muscle perfusion and oxygenation in individuals with diabetes mellitus. The study was performed in 4 healthy volunteers and 4 age-matched diabetic patients, at rest and during sustained isometric exercise. Significant attenuations in muscle perfusion and oxygenation were clearly observed in diabetic patients.

Andreas Boss¹, Nicholas Thomas Broskey², Roland Kreis¹, Francesca Amati^1,2, and Chris Boesch^1
1Depts Clinical Research and Radiology, University Bern, Bern, Switzerland, ²Dept of Physiology, University of Lausanne, Lausanne, Switzerland

We assessed oxidative capacity using the rate k of phosphocreatine recovery in age-matched elderly (60-80y) endurance-trained (N=11) and sedentary subjects (N=13). Mitochondrial volume density (MitoVD) was determined from muscle biopsies using electron microscopy. k was significantly increased (p=0.01) in the trained, which was paralleled by a ~50% greater MitoVD (p=0.02). Furthermore, k was significantly correlated with MitoVD (r2=0.46, p<0.003), and the ratio k to MitoVD was similar between trained and sedentary. This indicates that in age-matched elderly subjects, the greater muscle oxidative capacity in trained is due to increased mitochondrial volume, but not necessarily enhanced function per mitochondrial volume.

Eric E. Sigmund¹, Dmitry S. Novikov¹, Steven Baete¹, Kecheng Liu², Jenny Bencardino³, and Els Fieremans^4
1Radiology, NYU Langone Medical Center, Bernard and Irene Schwartz Center for Biomedical Imaging, New York, NY, United States, ²Siemens Medical Systems, Cleveland, OH, United States, ³Radiology, NYU Langone Medical Center, New York, NY, United States, ⁴Radiology, New York University, New York, NY, United States

The microstructural sensitivity of diffusion tensor imaging (DTI) depends upon the experimental diffusion time. Combining time-dependent diffusion measurements with appropriate tissue modelling may enhance specificity by directly quantifying microstructure. We analyzed time-dependent stimulated echo DTI at 3 T in skeletal muscle of normal controls and suspected chronic exertional compartment syndrome (CECS) patients, before and after exercise, and used the random permeable barrier model to quantify free diffusion, fiber diameter, and membrane permeability. Overall, patients showed significantly larger free diffusion changes, smaller diameter changes, and larger permeability increases than controls. Results are considered in light of microscopic changes in CECS pathophysiology.

Usha Sinha¹, Ali Moghadasi², Ryuta Kinugasa³, and Shantanu Sinha^4
1Physics, San Diego State University, San Diego, CA, United States, ²University of California at San Diego, San Diego, CA, United States, ³Human Science, Kanagwa University, Kanagawa, Japan, ⁴Radiology, University of California at San Diego, San Diego, CA, United States

Strain rate describes the rate of regional deformation and does not require 3Dal tracking, or a reference state since strain rate is an instantaneous measure of kinematic properties. Further, measurement of strain rate in young and old subjects will help characterize and elucidate age related changes in muscle structure and function. The strain rate tensor orientation deviated significantly from the muscle fiber orientation in both young and old subjects and may be an index of structural integrity. The out-of-plane strain rate component was significantly increased in the older subjects indicating age related loss of structural integrity.