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Session: Poster session 2 (Odd numbers)
Session starts: Friday 27 January, 10:00
Presentation starts: 10:00

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Zülal Kizilaslan (Eindhoven University of Technology)
Marcel Rutten (Eindhoven University of Technology)
Frans van de Vosse (Eindhoven University of Technology)
Richard Lopata (Eindhoven University of Technology)

Abstract:
Measuring the biomechanical change of skin can be used to detect skin diseases and monitor the development of skin problems such as pressure ulcers [1]. The objective of this study is to develop an experimental setup to estimate the mechanical properties of skin based on quasi-static ultrasound (US) elastography, a technique used to estimate biomechanical quantities and properties of tissue (such as strain and modulus), non-invasively [2]. For an in vitro feasibility test, phantoms were created using a 15 weight percent (wt%) polyvinylalcohol (PVA) solution subjected to 1 to 3 freeze-thaw cycles. For acoustic scattering, 3 weight percent silicon carbide was added to the PVA mixture. The skin mimicking phantoms were deformed while performing ultrasound imaging. To create a heterogeneous deformation field and measure the load exerted by the ultrasound probe, a water-filled, small diameter latex balloon (Cattex, Casalvieri, Italy) was used. This balloon was attached to a pressure sensor and positioned between a linear array probe (Esaote Europe, 10MHz) and the upper surface of the phantom. During compression, radio frequency data were recorded and exported to a PC. Data were processed for image reconstruction, and strain imaging was performed offline. Local strains were determined for each frame using a 2-D block matching technique, both implemented in MATLAB. The pressure inside the balloon was measured using a pressure sensor (P10EZ, BD, Vianen, the Netherlands). A Finite Element (FE) Model was developed to verify the US results. The 3D FE model consists of the PVA phantom, the water-filled balloon, and the probe as indenter, all implemented in ABAQUS (Dassault Systèmes, France). Displacement and strain fields were estimated throughout the compression experiments. The FEA shows similar deformation patterns as measured with ultrasound. However, the water pressure is currently still overestimated which might be caused by the current contact definition. In future work, the FEA model will be improved further, and the combination of measurement and model will be used to characterize the local mechanical properties of the phantom and eventually those of skin tissue.