A speckle target adaptive imaging technique in the presence of distributed aberrations

Abstract

Acoustic velocity inhomogeneities in tissue result in aberration of ultrasound images. These aberrations can be modeled as a near field thin phase screen or as a distributed aberrator. The effect of a near field thin phase screen is to time shift the received echo at each element, while distributed aberrators result in both pulse distortions and time shifts from element to element. Most current techniques for the correction of distributed aberrators are limited to application on point targets. A new technique is proposed which uses multiple transmits from spatially shifted transmit apertures (the translating transmit aperture algorithm), in conjunction with phase conjugate filters, to correct for distributed aberrations in the presence of speckle targets. The performance of the translating transmit aperture algorithm in improving the correlation between signals received by elements of different spatial separations is measured, and factors affecting the performance of this technique are investigated in simulation and experiment.

The application of k-space in pulse echo ultrasound

“…The echo coherence predicted in k s -space is in reasonable agreement with that found in simulation [24], [25] and in experiments [26], [29]. Simulations and experiments both showed correlations slightly lower than those predicted in k s -space.…”

“…The decorrelation predicted in k s -space is in excellent agreement with that previously found theoretically [23], in simulations [24], [25] and in experiments [23], [25], [26]. The RF decorrelation curve closely resembles the triangle function originally predicted by Mallart and Fink [23]; however, the k s -space prediction has a slight kink near its peak that was not present in previous theoretical analysis.…”

Ultrasonically-Induced Vaporization of Perfluorocarbon Droplets for Occlusion Therapy of Breast Cancer

“…Phase-and other beam-aberration corrections have been investigated by various groups (Karaman et al 1993;Ng et al 1997;Walker and Trahey 1996). Possible solutions include imaging of known and naturally existing structures (e.g., speckle, Ng et al 1997) and point targets in or near the volume of interest (VOI) (Walker and Trahey 1996;O'Donnell and Flax 1988). The backscatter of those structures is used to adjust the beam forming for that specific site, according to some model of the target structure and the propagation medium.…”

“…For example, deviations from that distribution can be used to correct for phase aberrations. Recent investigations include complex algorithms based on near field signal redundancy and shifted multi transmit subapertures [26]- [30].…”

Distributed aberrators for emulation of ultrasonic pulse distortion by abdominal wall

“…[7][8][9][10] Experimental demonstrations of these techniques were frequently limited in scope by explicit inclusion of the phase screen model in the apparatus, often in the form of a silicone rubber layer with nonuniform thickness. 4,[8][9][10] Furthermore, the phase screen models were sometimes restricted to arrival time variations along the lateral dimension of the aperture and thus neglected the effects of wavefront distortion along the out-of-plane dimension. A threedimensional distributed aberration phantom is desirable to avoid these compromises and facilitate realistic, controlled experiments without the complications introduced by handling and storage of tissue specimens.…”