Estimation of tissue stiffness using a prototype of air-float stiffness probe

This paper presents a novel technique for estimating stiffness distribution of a soft tissue using a prototype of air-float stiffness probe. The air-float stiffness probe uses an indentation technique to estimate tissue stiffness. It consists of a spherical indenter and an indentation depth sensing mechanism that operates under a supply of compressed air. The probe has the ability to estimate tissue stiffness in non-planner tissue profiles. A novel technique to estimate indentation force, using supply air pressure is described and validated using both experimental procedures and finite element analysis (FEA) techniques. FEA package, ANSYS CFX was used for analyzing in 2D the solid-fluid interactions within the probe to estimate force available at the indenter at different supply air pressure settings. Both the experimental results and numerical simulations suggest that there is a very strong linear correlation between the indentation force and the supply air pressure. This relationship is used to estimate the indentation force in real time during an indentation test. Verification tests carried out on simulated silicon samples showed that the probe is capable of estimating tissue stiffness values with high accuracy and repeatability.