2009
DOI: 10.1109/tuffc.2009.1327
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Energy-based adaptive focusing of waves: application to noninvasive aberration correction of ultrasonic wavefields

Abstract: An aberration correction method based on the maximization of the wave intensity at the focus of an emitting array is presented. The potential of this new adaptive focusing technique is investigated for ultrasonic focusing in biological tissues. The acoustic intensity is maximized noninvasively through direct measurement or indirect estimation of the beam energy at the focus for a series of spatially coded emissions. For ultrasonic waves, the acoustic energy at the desired focus can be indirectly estimated from… Show more

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Cited by 39 publications
(47 citation statements)
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“…It perfectly fits with the use of a phase-only SLM and it also maximizes the measured intensity and consequently improves the experimental signal to noise ratio (SNR) [21]. For all Hadamard basis vectors, the intensity is measured on the canonical basis of the pixels on the CCD camera and an observed transmission matrix K obs is acquired, which is related to the real one K by K obs ¼ K Â S ref , where S ref is a diagonal matrix representing the static reference.…”
mentioning
confidence: 68%
“…It perfectly fits with the use of a phase-only SLM and it also maximizes the measured intensity and consequently improves the experimental signal to noise ratio (SNR) [21]. For all Hadamard basis vectors, the intensity is measured on the canonical basis of the pixels on the CCD camera and an observed transmission matrix K obs is acquired, which is related to the real one K by K obs ¼ K Â S ref , where S ref is a diagonal matrix representing the static reference.…”
mentioning
confidence: 68%
“…MR-ARFI based phase aberration correction techniques [3][4] consider the measured displacement phase as an estimate of the beam's intensity pattern. These techniques measure the change in displacement magnitude at the focus due to each element's phase and derive the optimum phase correction for all elements analytically [3][4][5] using transducer groupings derived from basis functions or iteratively [6]. Many displacementmeasurements per element are required to recover the focal intensity (4 x number of transducer elements [3], resulting in about 2000-4000 pretreatment ultrasound pulses for different transcranial MRgFUS systems).…”
Section: Introductionmentioning
confidence: 99%
“…The intensity is then measured at the intended focal point. This can be done directly in measuring the pressure field with a hydrophone or, in the case of a soft elastic medium, in measuring the displacement induced at the focal point by the radiation force, which is proportional to the acoustic intensity [157]. Then the phase of the first transducer is cycled between 0 and 2π while the intensity is recorded.…”
Section: Phase One: Spatial Focusingmentioning
confidence: 99%
“…Narrowband optimization by the Hadamard method. Instead of using such an optimization scheme element by element, we perform a basis transformation to construct virtual transmittersÊ j , defined as linear combinations of real ones, which greatly improves the sensitivity of the method and reduces the number or iterations [157]. The coefficients of the combination are taken as the columns H n (1 < n < N ) of an N by N Hadamard matrix H, with elements H jn {−1; 1}.…”
Section: Optimal Spatiotemporal Focusing Through Random Mediamentioning
confidence: 99%
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