Ultrasonic imaging methods for quantitative musculoskeletal tissue assessment and improved prosthetic interface design

Abstract

For persons living with lower extremity amputation, the prosthetic socket -- the cup-like interface connecting the residuum to prosthesis - is considered the most critical component. It must be custom-made and tailored to each individual user, and if not fit properly can significantly hinder quality of life. As an alternative to conventional fabrication practices that involve subjective input from a clinician, computational modeling-based socket design practices have emerged. Despite early success, its clinical implementation and potential for broad accessibility are limited since it relies on expensive imaging technologies and robotic indentation devices. Medical ultrasound imaging, a cost-effective modality that can be used at the bedside, is a promising and clinically-viable solution. In order for ultrasound to become a viable scanning method for this application, technological development was necessary that allows for three-dimensional acquisition of (1) limb geometry and (2) mechanical tissue properties. Toward this goal, we first present the design of a novel multi-modal imaging system for rapidly acquiring volumetric ultrasound imagery of human limbs. Second, we present results of two studies that evaluate the use of ultrasound indentation and shear wave elastography (SWE) to characterize tissue biomechanics: the former to investigate how SWE is affected by transducer force, and the latter presenting a novel approach for constitutive parameter identification using a combination of finite element analysis (FEA), indentation, and SWE. Finally, we demonstrate that SWE may be performed using a non-contact approach, allowing for human limb data to be collected under discrete transducer-independent loading conditions. The techniques and results presented in this thesis highlight the potential for ultrasound imaging for improved prosthesis design, as well as more broadly to quantitative musculoskeletal tissue assessment for a variety of clinical applications. Specifically, data may be directly incorporated into computational prosthetic socket design practices that are in development in the Biomechatronics Group.