In-Vivo Soft Tissues Mechanical Characterization: Volume-Based Aspiration Method Validated on Silicones

Abstract

Simulating the deformations of soft tissues has gained importance in recent years due to the development of 3D patient-specific biomechanical models in the context of Computer Assisted Medical Interventions. To design such models, the mechanical behavior of each soft tissue has to be characterized in-vivo. In this paper, a volume-based aspiration method for in-vivo mechanical characterization of soft tissues was validated on synthetic materials. For this purpose, two silicones with slightly different stiffnesses were made. Samples were characterized using (1) aspiration, and, as references, two classical tests such as (2) uniaxial and (3) equibiaxial extension tests. Performing a Finite Element (FE) inverse identification on the experimental results provided Young's moduli similar to classical tests with about 7% maximum overestimation for the two silicones. This highlighted a significant improvement of the measurement method accuracy compared to the literature (about 30% relative overestimation).

Bilayer Stiffness Identification of Soft Tissues by Suction

“…The results of these two circuits are combined to provide the global pressurevolume curve (∆P tissue test − ∆V syringe test ). The general idea is that this curve can be transformed into the tissue pressure-volume curve (∆P tissue test − ∆V tissue i ) [20,38,39], where ∆V tissue i is the volume of tissue aspirated into the cup of suction diameter D i (figure 2 a and b).…”

“…Several attempts have been proposed to non-invasively identify mechanical properties of soft tissues in vivo [12,[16][17][18][19][20][21]. Suction-based set-ups, in particular, have received a lot of attention for the characterisation of the quasi-static mechanical response of the superficial soft in vivo [22].…”

“…Such a change in the method enables the elimination of camera, mirror, prism, and all the electronic parts from the system suction head that was basically reduced to a simple tube with an aperture. The corresponding family of devices, called VLASTIC, enables the evaluation of silicone stiffness with a maximum error of about 10% compared to uniaxial tensile tests [20]. It was also used in a clinical study to evaluate tongue stiffness in ten patients for two conditions: at rest and under general anesthesia [39].…”

In vivo measurement of breast tissues stiffness using a light aspiration device

“…This was done using homogenous silicone phantoms. Results obtained showed that errors in stiffness estimations remained below 7% (Elahi et al, 2019). The method has been used in a clinical pilot study to measure the tongue stiffness assuming an isotropic homogeneous material for tongue tissue (Kappert et al, 2021).…”

“…Because of the vacuum pressure, the portion of the tissue under the aperture is partially aspirated, with an amount of aspiration related to tissue stiffness. Our group recently proposed to use a light disposable aspiration system reduced to a simple tube 80 with a customisable (in size, shape and material) head aperture, able to meet any required severe sterilisation process (Elahi et al (2018); Elahi et al (2019); Connesson et al (2022) under review). This method, called VLASTIC, has been validated by comparing its estimations of synthetic material stiffness with the ones measured with classical experimental tensile tests.…”