Mechanical models for soft human organs are necessary for a variety of medical applications, such as surgical planning, virtual reality surgery simulators, and for diagnostic purposes. An adequate quantitative description of the mechanical behaviour of human organs requires high quality experimental data to be acquired and analyzed. We present a novel technique for the acquisition of such data from soft tissues and its post processing to determine some parameters of the tissue's mechanical properties. A small tube is applied to the target organ and a weak vacuum is generated inside the tube according to a predefined pressure history. A video camera grabs images of the deformation profile of the aspirated tissue, and a pressure sensor measures the correspondent vacuum level. The images are processed and used to inform the fitting of uniaxial and continuum mechanics models. Whilst the aspiration test device has been designed to fulfill the requirements for in-vivo applications, for measurements obtained during open surgery, initial experiments performed on human cadaveric tissues demonstrate the ability to both differentiate between different organs and also between normal and diseased organs on the basis of the derived mechanical properties.
Abstract. Constitutive models for soft biological tissues and in particular for human organs are required for medical applications such as surgery simulation, surgery planning, diagnosis. In the literature the mechanical properties of biosolids are generally presented in "preconditioned" state, i.e. the stabilized conditions reached after several loading-unloading cycles. We hereby present experiments on soft tissues showing the evolution of the mechanical response in a series of loading and unloading cycles. The experimental procedure applied in this study is based on the so called "aspiration experiment" and is suitable for in-vivo applications under sterile conditions during open surgery. In the present study this technique is applied ex-vivo on bovine liver. A small tube is contacted to the target organ and a weak vacuum is generated inside the tube according to a predefined pressure history. Several identical loading and unloading cycles are applied in order to characterize the evolutive behaviour of the tissue. The experimental data are used to inform the fitting of uniaxial and threedimensional continuum mechanics models. This analysis demonstrates that a quasi-linear viscoelastic model fails in describing the observed evolution from the "virgin" to the preconditioned state. Good agreement between simulation and measurement are obtained by introducing an internal variable changing according to an evolution equation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.