Static mechanical assessment of elastic Young's modulus of tissue mimicking materials used for medical imaging.

Emerging medical imaging techniques usually provide quantitative diagnostic parameters. Since the description of a method for quantitative imaging of strain and elastic modulus distributions in soft tissues by Ophir et al. in 1991, research in elastography is progressing and experimental in vitro validation of new displacement estimators appears crucial for clinical applications. Materials mimicking biological tissues appear very useful to reach this goal. Nevertheless, correct validation necessitates knowledge of mechanical properties of the investigated material, which are often difficult to obtain. This study describes a simple method for mechanical characterization of gels used in elastography. We demonstrated the possibility to assess elasticity modulus with a reasonable reproducibility using simple tools and methods. For validation, the described method was further tested with 5 samples of Polyvinyl alcohol (PVA) cryogel having different values of elasticity. Young's moduli, from 24 to 135 kPa according to the number of freeze-thaw cycles (from 1 to 5) have been measured with a reproducibility varying from 2 to 7%, in the respect of strict measurements conditions. The method demonstrates good feasibility and acceptable reproducibility to mechanically characterize phantoms.