Full experimental modelling of a liver tissue mimicking phantom for medical ultrasound studies employing different hydrogels |
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Authors: | Sergio Casciaro Francesco Conversano Stefano Musio Ernesto Casciaro Christian Demitri Alessandro Sannino |
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Affiliation: | (1) Institute of Clinical Physiology, National Council of Research (IFC-CNR), c/o Campus Ecotekne, via per Monteroni, 73100 Lecce, Italy;(2) Bioengineering Division, Euro Mediterranean Scientific Biomedical Institute, Brindisi, Italy;(3) Department of Engineering for Innovation, University of Salento, Lecce, Italy |
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Abstract: | Tissue mimicking phantoms have been widely reported to be an important tool for development, optimisation and performance
testing of ultrasound-based diagnostic techniques. In particular, modern applications of tissue mimicking phantoms often include
characterisation of the nonlinear behaviour of experimental ultrasound contrast agents. In such cases, the tissue-mimicking
materials should be chosen not only based on the values of their density, speed of sound and attenuation coefficient, but
also considering their effect on the appearance of “native harmonics” due to nonlinear distortion of ultrasound signal during
propagation. In a previous paper it was demonstrated that a cellulose-based hydrogel is suitable to simulate nonlinear acoustical
behaviour of liver tissue for thicknesses up to 8 cm. In this paper we present the experimental characterisation of the nonlinear
acoustical behaviour of a different polyethylene glycol diacrylate (PEGDA)-based hydrogel, in order to assess whether and
how it can improve the performances and overcome some limitations of the cellulose-based hydrogel as liver tissue-mimicking
material. Samples of pig liver tissue, cellulose-based hydrogel and PEGDA-based hydrogel were insonified in a through-transmission
set-up, employing 2.25-MHz pulses with different mechanical index (MI) values. Second harmonic and first harmonic amplitudes
were extracted from the spectra of received signals and their difference was then used to compare sample behaviours. Obtained
results show how a new more accurate and combined experimental model of linear and nonlinear acoustical behaviour of liver
tissue is feasible. In fact, a further confirmation of the cellulose-based hydrogel effectiveness to precisely simulate the
liver tissue for penetration depths up to 8 cm was provided, and it was also shown that the employment of the PEGDA-based
hydrogel can extend the range of useful tissue-mimicking material thicknesses up to 11 cm, moreover allowing a considerable
improvement of the time stability and behaviour reliability of the corresponding manufactured phantoms. |
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