Quasi-linear Viscoelastic Characterization of Soft Tissue-mimicking Materials

We present a novel method based on quasi-linear viscoelasticity (QLV) to describe the time-dependent behavior of soft materials. Unlike previous methods for deriving QLV parameters, we characterize the elastic and viscous behavior of materials separately by using two different sets of experiments. To model the nonlinear elastic behavior, we fit the elastic stress response with a one-term Ogden model. Then, we model the relaxation behavior with a Prony series to compare the stress relaxation of the material at different timescales. This new method allows us to uniquely characterize materials with narrow confidence intervals (high accuracy), independently from the loading conditions. We validate our model using samples made of phantom materials that mimic normal and cancerous prostate tissues in terms of Young's modulus. Drawing a precise distinction between the phantoms, this method demonstrates the potential for prostate cancer diagnosis. Our model is also shown to distinguish materials with the same elastic (viscous) properties but different viscous (elastic) properties. We believe the proposed method provides the foundation for early diagnosis of prostate cancer in the future.

The experiments were performed by the mechanical tester Mach-1 V500CS (Biomomentum Inc., Laval, QC, Canada).