Combining Freehand Ultrasound-Based Indentation and Inverse Finite Element Modeling for the Identification of Hyperelastic Material Properties of Thigh Soft Tissues

Abstract

Finite element analysis (FEA) is a numerical modeling tool vastly employed in research facilities to analyze and predict load transmission between the human body and a medical device, such as a prosthesis or an exoskeleton. Yet, the use of finite element modeling (FEM) in a framework compatible with clinical constraints is hindered by, among others, heavy and time-consuming assessments of material properties. Ultrasound (U.S.) imaging opens new and unique opportunities for the assessment of in vivo material properties of soft tissues. Confident of these advances, a method combining a freehand U.S. probe and a force sensor was developed in order to compute the hyperelastic constitutive parameters of the soft tissues of the thigh in both relaxed (R) and contracted (C) muscles' configurations. Seven asymptomatic subjects were included for the experiment. Two operators in each configuration performed the acquisitions. Inverse FEM allowed for the optimization of an Ogden's hyperelastic constitutive model of soft tissues of the thigh in large displacement. The mean shear modulus identified for configurations R and C was, respectively, 3.2 ± 1.3 kPa and 13.7 ± 6.5 kPa. The mean alpha parameter identified for configurations R and C was, respectively, 10 ± 1 and 9 ± 4. An analysis of variance showed that the configuration had an effect on constitutive parameters but not on the operator.

In vivo quantification of 3D displacement in sacral soft tissues under compression: Relevance of 2D US-based measurements for pressure ulcer risk assessment

“…However, if confirmed in larger sample, the implications of our results could go far beyond the scope of the PU prevention. While not providing the information about the out-of-plane tissue movement and anisotropy, US imaging and associated correlation techniques are indeed used to investigate biomechanical properties of various soft tissues including fascia (Langevin et al 2011), the intervertebral disc (Vergari et al 2014) and thigh (Fougeron et al 2020). Results of the current study suggest that the 2D US should be used with caution for the evaluation of tissue motion.…”

Calibration of the fat and muscle hyperelastic material parameters for the assessment of the internal tissue deformation in relation to pressure ulcer prevention

“…An ultrasound acquisition of the subdermal tissue in the region above the superior process of median sacral crest was performed using a commercial device (Aixplorer, SuperSonic Imagine, France) with a linear ultrasound (US) probe of 8 MHz central frequency (SuperLinear SL 15-4). Custom made load sensor was attached to the ultrasound probe (Fougeron et al 2020). Several cycles of the indentation with the probe were performed and the one with the clearest video frames in the beginning and the end of the indentation cycle was chosen as a basis to build a 2D finite element (FE) model in Ansys 19.2 software.…”

Tools for computational analysis of moving boundary problems in cellular mechanobiology

“…Larger deformations require nonlinear hyperelastic models such as the neo‐Hookean solid (Arefi, Tsvirkun, Verdier, & Feng, 2020). A major drawback of these more realistic models, however, is the difficulty of parameterizing them based on experimental data (Fougeron et al, 2020; Mihai & Goriely, 2017; Valero, Navarro, Navajas, & García‐Aznar, 2016).…”