Post-processing enhancement of reverberation-noise suppression in dual-frequency SURF imaging

Abstract

A post-processing adjustment technique to enhance dual-frequency second-order ultrasound field (SURF) reverberation-noise suppression imaging in medical ultrasound is analyzed. Two variant methods are investigated through numerical simulations. They both solely involve post-processing of the propagated high-frequency (HF) imaging wave fields, which in real-time imaging corresponds to post-processing of the beamformed receive radio-frequency signals. Hence, the transmit pulse complexes are the same as for the previously published SURF reverberation-suppression imaging method. The adjustment technique is tested on simulated data from propagation of SURF pulse complexes consisting of a 3.5-MHz HF imaging pulse added to a 0.5-MHz low-frequency soundspeed manipulation pulse. Imaging transmit beams are constructed with and without adjustment. The post-processing involves filtering, e.g., by a time-shift, to equalize the two SURF HF pulses at a chosen depth. This depth is typically chosen to coincide with the depth where the first scattering or reflection occurs for the reverberation noise one intends to suppress. The beams realized with post-processing show energy decrease at the chosen depth, especially for shallow depths where, in a medical imaging situation, a body-wall is often located. This indicates that the post-processing may further enhance the reverberation- suppression abilities of SURF imaging. Moreover, it is shown that the methods might be utilized to reduce the accumulated near-field energy of the SURF transmit-beam relative to its imaging region energy. The adjustments presented may therefore potentially be utilized to attain a slightly better general suppression of multiple scattering and multiple reflection noise compared with non-adjusted SURF reverberation-suppression imaging.

SURF imaging beams in an aberrative medium: Generation and postprocessing enhancement

“…Beams, from left to right within each za pane group: hSH, τ SH, hSI, and τ SI. beams and the fundamental beams align well with what was found for the same 2-D axisymmetric simulations in [2]. The filter-adjusted SURF beams do however show worse and more unstable Q za in the present 3-D simulations than in the referred work.…”

“…The post-processing suppression depth adjustment methods, as previously implemented in [2] for a homogeneous medium, are here shown to be feasible on the simulated aberrated fields also within an inhomogeneous medium.…”

“…This approach is chosen to in some extent better emulate how anà priori determination of h za could be performed by experimental field characterization. The averaging over the region S, which was not performed in [2], is introduced to take a finite hydrophone width into account. The determination of h za in a real medical imaging setup may be more cumbersome, as further discussed in [2].…”

“…This work concerns dual-frequency transmit-beams that are utilized for reverberation noise suppression in ultrasound image reconstruction by use of methods analyzed in [1,2]. The developments of the current paper regard the feasibility of such beam generation within an inhomogeneous medium that generates sound-speed variations that aberrate the beam.…”

A model and regularization scheme for ultrasonic beamforming clutter reduction

“…There are also several new methods that suppress multipath clutter. One new method is second-order ultrasound field (SURF) imaging, which takes advantage of nonlinear wave propagation by directly manipulating nonlinear propagation in a way that specifically targets the multipath scattering problem [19], [23–25]. SURF imaging is promising, but it may be some time before the necessary high-bandwidth transducers and arbitrary transmitters are readily available [19].…”