In vivo imaging of the skin in the 100 MHz region using the synthetic aperture concept

A major design problem concerning medical high frequency broadband imaging systems is caused by the strong attenuation of the tissue, which limits the maximum depth of penetration and the achieveable signal-to-noise-ratio (SNR). To address this problem, strongly focused transducers with a high energy density in a narrow focal region are utilized. To achieve images of high quality and resolution over a large depth range despite the short depth of field of those devices, the Synthetic Aperture Focusing Technique (SAFT) is employed. For SAFT-processing, the focus area is considered as a virtual source of approximately spherical waves. This hypothesis is supported by a simulation of the point-spread-function of a focused transducer, which is based on the Rayleigh-Sommerfeld-integral in the time domain.