title: Iteration of transmit-beam aberration correction in medical ultrasound imaging.
abstract: Simulations of iterative transmit-beam aberration correction using a time-delay and amplitude filter have been performed to study the convergence of such a process. Aberration in medical ultrasonic imaging is usually modeled by arrival-time and amplitude fluctuations concentrated on the transducer array. This is an approximation of the physical aberration process, and may be applied to correct the transmitted signal using a time-delay and amplitude filter. Estimation of such a filter has proven difficult in the presence of severe aberration. Presented here is an iterative approach, whereby a filter estimate is applied to correct the transmit-beam. This beam induces acoustic backscatter better suited for arrival-time and amplitude estimation, thus facilitating an improved filter estimate. Two correlation-based methods for estimating arrival-time and amplitude fluctuations in received echoes from random scatterers were employed. Aberration was introduced using eight models emulating aberration produced by the human abdominal wall. Results show that only a few iterations are needed to obtain corrected transmit-beam profiles comparable to those of an ideal aberration correction filter. Furthermore, a previously developed focusing criterion is found to quantify the convergence accurately.
authors.affiliation: Department of Circulation and Imaging, Norwegian University of Science and Technology, Trondheim, 7489 Norway.
authors.forename: Svein-Erik
authors.initials: SE
authors.lastname: Måsøy
authors.forename: Trond
authors.initials: T
authors.lastname: Varslot
authors.forename: Bjørn
authors.initials: B
authors.lastname: Angelsen
mesh_terms: D006801:Humans; D008962:Models, Theoretical; D014463:Ultrasonography