A theoretical investigation of ultrasonic transducer design for measurement of skin

Despite significant advances in ultrasonic instrumentation, accurate and repeatable measurements of skin structure and dimensions remain problematic. Skin structure is complicated and structural boundaries are non-planar and may be diffuse, inhibiting the application of inversion methods for skin thickness measurement. Coupling a transducer to the skin surface with water or aqueous gel can produce significant artefacts in thickness measurement, which may be prevented by using a rubber dry contact. This work describes a theoretical investigation of these problems, using the PZFlex finite element code as a virtual prototyping tool. Simulations show that non-planar and diffuse boundaries have significant effect on the output backscattered signals; and using of low loss rubber dry contact is possible but further work is required to determine the properties and optimum shape of the rubber interface.