Hyperelastic Strain Elastography to Measure Subcutaneous Adipose Tissue and Muscle Thickness: a Simulation Study

Many different methods are available to find the overall body fat percentage. A-mode, as well as B-mode of ultrasound, have also been explored to measure Subcutaneous Adipose Tissue (SAT) thickness locally on different parts of the human body. These measurements are dependent on manual delineation of fat-muscle boundary and thus prone to error. It is known that there is a good contrast in elastic modulus of adipose tissue (1-5 kPa) and muscle tissue (6-150 kPa). This contrast can be useful for SAT thickness measurement using strain elastography. Also, in the current ultrasonic strain elastography technique, there is a limitation that tissue is considered linear elastic and hence limited to small strain deformations. This study advances the field by employing a Hyperelastic model theory and enabling us to perform quantitative measurements of shear modulus for large strains. We present results of a 1D simulation study to measure strain contrast between adipose tissue and muscle layer considering hyperelastic properties of the respective layers and local strains up to $40 %$. Hyperelastic Strain Elastography (HESE) can serve as an easy method to find localized SAT thickness and characterization of hyperelastic tissues. A portable device can be made using HESE in $1 D$ to measure localized SAT as well as muscle thicknesses.