Time exposure acoustics

Norton, Stephen J.; Won, I. J.

doi:10.1109/36.843027

Cited by 72 publications

(80 citation statements)

References 5 publications

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“…66 Images were formed using a modified version of the beamforming algorithm described in Ref. 48, known as "time exposure acoustics," which was adapted to include correction terms to account for the acoustic propagation through skull bone. 73 First, a grid of points are prescribed over which the image reconstruction will take place.…”

Section: E Image Formationmentioning

confidence: 99%

“…However, the information obtained from a single-element PCD is fundamentally limited due to the inherent trade-off between the volume of sensitivity and spatial specificity of the device. The use of multielement arrays, combined with passive beamforming algorithms borrowed from other fields, [45][46][47][48] has been shown to overcome this limitation and enable spatial mapping of cavitation activity during the application of FUS in both in vitro [49][50][51][52][53][54][55][56][57][58][59][60][61][62] and in vivo [63][64][65][66][67] settings. The integration of passive imaging during mechanicalbased FUS brain therapies would make the procedures practical, by providing a method for real-time treatment monitoring and control.…”

Section: Introductionmentioning

confidence: 99%

“…[69][70][71][72] One approach to utilizing passive imaging in the brain could be to image through these windows using a narrowaperture array. 64,65 However, due to the superior resolution afforded by large apertures while employing passive imaging techniques, 48 an implementation with an array covering the entire skull surface would be optimal.…”

Section: Introductionmentioning

confidence: 99%

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Experimental demonstration of passive acoustic imaging in the human skull cavity using CT‐based aberration corrections

Jones

O’Reilly

Hynynen³

2015

Medical Physics

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Purpose: Experimentally verify a previously described technique for performing passive acoustic imaging through an intact human skull using noninvasive, computed tomography (CT)-based aberration corrections Jones et al. [Phys. Med. Biol. 58, 4981-5005 (2013)]. Methods: A sparse hemispherical receiver array (30 cm diameter) consisting of 128 piezoceramic discs (2.5 mm diameter, 612 kHz center frequency) was used to passively listen through ex vivo human skullcaps (n = 4) to acoustic emissions from a narrow-band fixed source (1 mm diameter, 516 kHz center frequency) and from ultrasound-stimulated (5 cycle bursts, 1 Hz pulse repetition frequency, estimated in situ peak negative pressure 0.11-0.33 MPa, 306 kHz driving frequency) Definity™ microbubbles flowing through a thin-walled tube phantom. Initial in vivo feasibility testing of the method was performed. The performance of the method was assessed through comparisons to images generated without skull corrections, with invasive source-based corrections, and with water-path control images. Results: For source locations at least 25 mm from the inner skull surface, the modified reconstruction algorithm successfully restored a single focus within the skull cavity at a location within 1.25 mm from the true position of the narrow-band source. The results obtained from imaging single bubbles are in good agreement with numerical simulations of point source emitters and the authors' previous experimental measurements using source-based skull corrections O'Reilly et al. [IEEE Trans. Biomed. Eng. 61, 1285-1294]. In a rat model, microbubble activity was mapped through an intact human skull at pressure levels below and above the threshold for focused ultrasound-induced blood-brain barrier opening. During bursts that led to coherent bubble activity, the location of maximum intensity in images generated with CT-based skull corrections was found to deviate by less than 1 mm, on average, from the position obtained using source-based corrections. Conclusions: Taken together, these results demonstrate the feasibility of using the method to guide bubble-mediated ultrasound therapies in the brain. The technique may also have application in ultrasound-based cerebral angiography. C 2015 American Association of Physicists in Medicine.

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Section: E Image Formationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental demonstration of passive acoustic imaging in the human skull cavity using CT‐based aberration corrections

Jones

O’Reilly

Hynynen³

2015

Medical Physics

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“…However, since axial resolution for pulse-echo sonography depends on pulse length, which increases with decreasing frequency, this approach sacrifices resolution and has limited the use of ultrasound to imaging major vessels. 10,11 Here, we use a passive technique similar to those previously used in acoustics 12 and seismic imaging, 13 modifications of which have more recently been investigated to map cavitation activity during ultrasound therapy. 14,15 With passive beamforming techniques both the phase and amplitude information of the received signals are considered and axial resolution primarily depends on frequency and array aperture, and not on pulse length.…”

Section: Introductionmentioning

confidence: 99%

“…16 Additionally, the intensity of the scatter response can be integrated over time to hugely improve the signal to noise ratio (SNR). 13 Finally, to overcome the skull attenuation we use a low frequency transmit array, and to increase the resolution we use a full hemispherical sparse receiver array. Large aperture transmit arrays are standard place in transcranial ultrasound therapy research, 17,18 but have not been used for brain imaging.…”

Section: Introductionmentioning

confidence: 99%

A super‐resolution ultrasound method for brain vascular mapping

2013

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Purpose: High-resolution vascular imaging has not been achieved in the brain due to limitations of current clinical imaging modalities. The authors present a method for transcranial ultrasound imaging of single micrometer-size bubbles within a tube phantom. Methods: Emissions from single bubbles within a tube phantom were mapped through an ex vivo human skull using a sparse hemispherical receiver array and a passive beamforming algorithm. Noninvasive phase and amplitude correction techniques were applied to compensate for the aberrating effects of the skull bone. The positions of the individual bubbles were estimated beyond the diffraction limit of ultrasound to produce a super-resolution image of the tube phantom, which was compared with microcomputed tomography (micro-CT). Results:The resulting super-resolution ultrasound image is comparable to results obtained via the micro-CT for small tissue specimen imaging. Conclusions: This method provides superior resolution to deep-tissue contrast ultrasound and has the potential to be extended to provide complete vascular network imaging in the brain.

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Delay multiply and sum beamforming method applied to enhance linear‐array passive acoustic mapping of ultrasound cavitation

et al. 2019

Medical Physics

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Purpose Passive acoustic mapping (PAM) has been proposed as a means of monitoring ultrasound therapy, particularly nonthermal cavitation‐mediated applications. In PAM, the most common beamforming algorithm is a delay, sum, and integrate (DSAI) approach. However, using DSAI leads to low‐quality images for the case where a narrow‐aperture receiving array such as a standard B‐mode linear array is used. This study aims to propose an enhanced linear‐array PAM algorithm based on delay, multiply, sum, and integrate (DMSAI). Methods In the proposed algorithm, before summation, the delayed signals are combinatorially coupled and multiplied, which means that the beamformed output of the proposed algorithm is the spatial coherence of received acoustic emissions. We tested the performance of the proposed DMSAI using both simulated and experimental data and compared it with DSAI. The reconstructed cavitation images were evaluated quantitatively by using source location errors between the two algorithms, full width at half maximum (FWHM), size of point spread function (A50 area), signal‐to‐noise ratio (SNR), and computational time. Results The results of simulations and experiments for single cavitation source show that, by introducing DMSAI, the FWHM and the A50 area are reduced and the SNR is improved compared with those obtained by DSAI. The simulation results for two symmetric or nonsymmetric cavitation sources and multiple cavitation sources show that DMSAI can significantly reduce the A50 area and improve the SNR, therefore improving the detectability of multiple cavitation sources. Conclusions The results indicate that the proposed DMSAI algorithm outperforms the conventionally used DSAI algorithm. This work may have the potential of providing an appropriate method for ultrasound therapy monitoring.

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Time exposure acoustics

Cited by 72 publications

References 5 publications

Experimental demonstration of passive acoustic imaging in the human skull cavity using CT‐based aberration corrections

Experimental demonstration of passive acoustic imaging in the human skull cavity using CT‐based aberration corrections

A super‐resolution ultrasound method for brain vascular mapping

Delay multiply and sum beamforming method applied to enhance linear‐array passive acoustic mapping of ultrasound cavitation

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