title: In Situ Mechanical Characterization of Multilayer Soft Tissue Using Ultrasound Imaging.
abstract: In this paper, we report the development of a technique to characterize layer-specific nonlinear material properties of soft tissue in situ with the potential for in vivo testing. A soft tissue elastography robotic arm system comprising of a robotically manipulated 30 MHz high-resolution ultrasound probe, a custom designed compression head, and load cells has been developed to perform compression ultrasound imaging on the target tissue and measure reaction forces. A multilayer finite element model is iteratively optimized to identify the material coefficients of each layer. Validation has been performed using tissue mimicking agar-based phantoms with a low relative error of ∼7% for two-layer phantoms and ∼10% error for three layer phantoms when compared to known ground-truth values obtained using a commercial material testing system. The technique has then been used to successfully determine the in situ layer-specific mechanical properties of intact porcine stomach. The mean C10and C20for a second-order reduced polynomial material model were determined for the muscularis (6.41 ± 0.60, 4.29 ± 1.87 kPa), submucosal (5.21 ± 0.57, 3.68 ± 3.01 kPa), and mucosal layers (0.06 ± 0.02, 0.09 ± 0.24 kPa). Such a system can be utilized to perform in vivo mechanical characterization, which is left as future work.
authors.forename: Saurabh
authors.initials: S
authors.lastname: Dargar
authors.forename: Ali C
authors.initials: AC
authors.lastname: Akyildiz
authors.forename: Suvranu
authors.initials: S
authors.lastname: De
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology*; D054459:Elasticity Imaging Techniques / Q000295:instrumentation / Q000379:methods*; D004867:Equipment Design; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012371:Robotics / Q000295:instrumentation; D012815:Signal Processing, Computer-Assisted; D013270:Stomach / Q000000981:diagnostic imaging; D013552:Swine