The progressive focusing correction technique for ultrasound beamforming

Abstract

Abstract-This work presents a novel method for digital ultrasound beamforming based on programmable table look-ups, in which vectors containing coded focusing information are efficiently stored, achieving an information density of a fraction of bit per acquired sample. Timing errors at the foci are within half the period of a master clock of arbitrarily high frequency to improve imaging quality with low resource requirements. The technique is applicable with conventional as well as with ∆Σ converters.The bit-width of the focusing code and the number of samples per focus can be defined to improve both memory size and F# with controlled timing errors. In the static mode, the number of samples per focus is fixed, and in the dynamic approach that figure grows progressively, taking advantage of the increasing depth of focus. Furthermore, the latter has the lowest memory requirements.The technique is well suited for research purposes as well as for real-world applications, offering a degree of freedom not available with other approaches. It allows, for example, modifying the sampling instants to phase aberration correction, beamforming in layered structures, etc. The described modular and scalable prototype has been built using low-cost field programmable gate arrays (FPGAs). Experimental measurements are in good agreement with the theoretically expected errors.

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“…The final square root calculation of the given binary number x requires multiplication of 2 m/2 at the final stage as given in (7). It requires left shifting the output of previous approximation with m/2 bits if m is even; and multiplication with 2 √ along with the left shifting if m is odd.…”

New ultrasound imaging techniques with phase coherence processing

“…2a, Section 2 starts at sample 118, Section 3 at sample 134 and so on. The breaking points are defined by the global range as [8],…”