Biomechanical Models for Soft Tissue Simulation

Information Technology is having an increasing influence on medicine. This can be readily observed by anybody visiting a hospital or consulting a doctor, or even by going to the chemist. A range of new medical instruments, new scanners, new on-line diagnostics as well as more effective distribution methods all increasingly contain IT elements that enable new more effective medical tools and services. But there is also a lot going on "behind the scenes", at the research and development level, that will greatly influence the medical tools and services of tomorrow. In this respect, Esprit, the European Commission's IT research program, has been supporting a range of research and development projects that are contributing to the opening of new avenues in the medical field. At the 1997 European IT Conference, a special exhibit has highlighted Esprit's contributions in the area, including, for example projects that have succeeded in developing: • a prototype visual prosthesis linked to the optic nerve (MIVIP) • implantable blood micro-pumps (IMALP) • new low-power pacemakers and defibrillators (HIPOCRA T) • new high-quality 3D ultrasound images (NICE) • realistic computer models of the human musculo-skeletal system (CHARM) CHARM, the last - but not least - of these, is further elaborated in this book.

Numerous experiments reported in the biomechanical literature have shown that soft tissues are highly nonlinear viscoelastic materials. Attempts to model their mechanical behaviour have led to different kinds of mathematical relationships depending on the approach adopted. The use of these models for the realistic simulation of skeletal soft tissues requires basic knowledge of the theory of nonlinear mechanics as well as knowledge of the associated incremental finite element methods. Although many documents have been published in these different areas, few of them give enough details to understand how the models are related to the underlying mechanical theory and how incremental methods are applied to achieve finite element simulations.
This report has been developed, as part of the European Esprit project CHARM, to provide an overview of the available models in light of theoretical mechanics and finite element methods, for the realistic simulation of the human muscles, tendons and skin.