In vivo measurement of solid organ visco-elastic properties

To support the ongoing development of software-based surgical simulation systems, work is underway to acquire the mechanical properties of living tissue. When such simulations include force feedback, visco-elastic properties must be evaluated over a range of frequencies relevant to human perception and motor control. A minimally invasive instrument has been developed which can perform normal indentation on solid organs, and apply and measure deformations over a frequency range from DC to approximately 100Hz. Measurement performance was validated on a series of objects and materials with known properties, and the device was subsequently used in in vivo tests on porcine liver. Results of these validation tests as well as the data extracted from the in vivo experiments are presented. Testing in ongoing, and will be expanded to more completely characterize liver, as well as porcine spleen and other solid organ tissues. While these animal tissue property tests are valuable in and of themselves, they pave the way for the development of instruments and experimental protocols suitable for the measurement of human tissue properties.