4C-3 Limited-Angle Spatial Compound Imaging of Skin with High-Frequency Ultrasound (20 MHz)

Ultrasound spatial compounding has been proven to successfully improve the image contrast, to achieve a more isotropic resolution and to reduce imaging artifacts in comparison with conventional B-mode imaging. For high- frequency ultrasound (HFUS) imaging of skin, usually linear scans only are performed perpendicularly to the axial direction of sound propagation. In this paper the potential of HFUS limited- angle spatial compounding for skin imaging is evaluated. We have implemented a new 20 MHz ultrasound system for limited- angle (up to plusmn40deg) spatial compound imaging. A sophisticated scanner was designed for high-resolution imaging with a spherically focused single-element transducer. The influence of unknown parameters of the system is eliminated by calibration measurements on a wire phantom. The imaging properties of the implemented system were assessed by means of phantom and in vivo measurements. A ray-tracing method for the compensation of artifacts, which are caused by refraction at the skin surface, is proposed and evaluated.