A new coded-excitation ultrasound imaging system. I. Basicprinciples

摘要

A new approach to ultrasound imaging with coded-excitation isnpresented. The imaging is performed by reconstruction of the scatterernstrength on an assumed grid covering the region of interest (ROI). Ournformulation is based on an assumed discretized signal model whichnrepresents the received sampled data vector as a superposition ofnimpulse responses of all scatterers in the ROI. The reconstructionnoperator is derived from the pseudo-inverse of the linear operatorn(system matrix) that produces the received data vector. The singularnvalue decomposition (SVD) method with appropriate regularizationntechniques is used for obtaining a robust realization of thenpseudo-inverse. Under simplifying (but realistic) assumptions, thenpseudo-inverse operator (PIO) can be implemented using a bank ofntransversal filters with each filter designed to extract echoes from anspecified image line. This approach allows for the simultaneousnacquisition of a large number of image lines. This could be useful innincreasing frame rates for two-dimensional imaging systems or allowingnfor real-time implementation of three-dimensional imaging systems. Whenncompared to the matched filtering approach to similar coded-excitationnsystems, our approach eliminates correlation artifacts that are known tonplague such systems. Furthermore, the lateral resolution of the newnsystem can exceed the diffraction limit imposed on conventional imagingnsystems utilizing delay-and-sum beamformers. The range resolution isncompared to that of conventional pulse-echo systems with resolutionnenhancement (our PIO behaves as a pseudo-inverse Wiener filter in thenrange direction). Both simulation and experimental verification of thesenstatements are given