Displacements under applied loading with MRI for the estimation of high-precision strains in soft tissues

Deva D Chan, Purdue University

Abstract

The human body experiences both internal and external forces on a daily basis. External forces range from ground reaction forces to traumatic events like head impacts, while internal forces are exerted on various tissues of the body by actions such as the constriction of muscle tissue, the passive stretch of connective tissues, and fluid pressurization in internal organs. The mechanical behavior of the numerous tissues of the body and their native mechanical environment are therefore tremendously important to understanding the structure and function of tissues that experience both internal and external forces. Noninvasive imaging techniques like magnetic resonance imaging (MRI) allow for high-contrast visualization of the morphology of most soft tissues. Additionally, various quantitative MRI techniques permit the characterization of tissues beyond just a qualitative evaluation of structure, including correlation with biochemical content and direct measurement of mechanical behavior. Among these, displacement encoding with stimulated echoes (DENSE) and similar techniques permit the measurement of displacements at each pixel of interest. This dissertation centers on the measurement of displacements under applied loading with MRI, or dualMRI. First, motivation is established for the development of a noninvasive imaging tool for the assessment of mechanical behavior of soft tissues, especially articular cartilage. Quantitative MRI techniques are discussed in the light of detecting cartilage damage, including assessment of its mechanical behavior. The dualMRI technique is then validated and demonstrated on a high-field research MRI system. Then, dualMRI is applied to characterize the changes in mechanical behavior after cartilage defect and with a tissue engineering implant within animal joints. Finally, the dualMRI technique is translated to use on a clinical MRI system, where it is validated and demonstrated in an ex vivo intervertebral disc section. The dissertation concludes with a discussion of the in vivo applications of dualMRI and, in particular, towards the measurement of displacements and strains within the tibiofemoral articular cartilage of a living human subjects.

Degree

Ph.D.

Advisors

Neu, Purdue University.

Subject Area

Biomedical engineering|Medical imaging|Biomechanics

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