Adaptive 150 MHz ultrasound imaging of the skin and the eye using an optimal combination of short pulse mode and pulse compression mode

A major design problem concerning medical broadband imaging systems is caused by the strong dispersive attenuation of the tissue, which results in inhomogeneous images with poor signal to noise ratio (SNR). To address the noise problem, strongly focused transducers with a high energy density in a narrow focal region are utilized, which also provide more isotropic images due to improved lateral resolution. To account for the short depth of the focal area a suitable imaging conception, the B/Z-scan concept (alternatively: B/D-Scan, B=/spl and/Brightness, D=/spl and/Depth) is used. To avoid the inhomogeneity of the images, different transmitter signals for each depth are applied, which are pseudoinversely prefiltered according to the transfer function of the covering tissue. To gain signal energy required for inverse filtering, a pulse compression technique with nonlinearly frequency modulated chirp signals is utilized.