Soft tissue characterization by dynamic impact analysis: Results on agar-based phantoms

The mechanical characterization of soft tissues is of great importance in different medical fields since a change of soft tissue properties may be of physio-pathologic nature. This study investigates the feasibility of using impact analysis to measure the mechanical properties of soft tissue mimicking phantoms made of agarose. The impact analysis is performed on agar-based specimens with various concentrations by applying small impacts on a beam in contact with the surface of the specimen. The time variation of the signal corresponding to the impact force is analyzed as a function of the agar concentration and the impact force amplitude. A temporal indicator τ is developed, corresponding to the time difference between the initial impact and the rebound of the beam on the hammer. The results show a decrease of τ when the agar concentration increases. The method appears to be sensitive to non-linear phenomena related to the material behavior and/or to contact phenomena between the beam and the specimen. The error on the estimation of the percentage of agar is of the same order of magnitude than the sensitivity obtained using elastography techniques. This study opens new perspective for fast, cheap, and non-invasive mechanical characterization of non-linear soft tissues.