The Use of Magnetic Resonance to Monitor Water Redistribution in Tendon Under Static Load

Christopher H. Sotak, Professor of Biomedical Engineering, Chemistry and Biochemistry, Biomedical Engineering Department, Worcester Polytechnic Institute

Friday, January 11, 2008

Spanos Auditorium

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This seminar is part of the Jones Seminars on Science, Technology, and Society series

Hydration is known to be an important factor in determining the static and viscoelastic properties of soft tissues. In the case of tendon, the role of water in determining the material properties under tensile load is not well understood. Gaining further understanding of how water is mobilized in tensile-loaded soft tissues may facilitate further development of micromechanical models of soft-tissue behavior. Magnetic resonance imaging (MRI) and spectroscopy (MRS) are particularly useful for non-invasive characterization of soft-tissue properties such as structure, permeability, or anisotropy. In rabbit Achilles tendon, the MR-derived apparent diffusion coefficient (ADC) of water is quite sensitive to changes in tissue structure/anisotropy as a function of tensile load. The change in ADC values of tendon water under tensile load may be due, in part, to the extrusion of water from the more restricted tendon core to a relatively unrestricted bulk phase at the periphery of the tendon. Tensile loading may also influence water ADC values by changing the spatial separation of restricting barriers (e.g., changes in tendon fibril packing density). We have employed both MRI and MRS to monitor changes in the MR properties of water (T1 and T2 relaxation times, proton density, and ADC) in rabbit Achilles tendon caused by variations in mechanical load. Porous-media theory has been used as a framework to explain the experimental changes in tendon-water ADC in response to mechanical perturbation.

About the Speaker

Christopher H. Sotak, PhD, holds the rank of Professor in the Biomedical Engineering (BME) Department at Worcester Polytechnic Institute (WPI). In almost 20 years at WPI, he has served as a faculty member as well as Department Head from 1999-2007. Prof. Sotak directs the NMR research laboratory, which is internationally known for applications of magnetic resonance imaging (MRI) and spectroscopy (MRS) methods in the evaluation of therapeutic interventions in cancer and stroke. Research also focuses on characterizing structural information in fluid-saturated porous media using diffusion-weighted MRI and MRS. The laboratory is part of the Conjoint MRS/MRI research program between the WPI BME Department and the Department of Radiology at the University of Massachusetts Medical School (UMMS) in Worcester. Prof. Sotak is on the editorial boards of a number of leading scientific journals in his field and is an Elected Fellow of the American Institute for Medical and Biological Engineering (AIMBE) and the International Society of Magnetic Resonance in Medicine (ISMRM).