Electronic Beam Steering Used with a Toroidal HIFU Transducer Substantially Increases the Coagulated Volume

Vincenot, Jérémy; Melodelima, David; Chavrier, F.; Vignot, Alexandre; Kocot, Anthony; Chapelon, Jean‐Yves

doi:10.1016/j.ultrasmedbio.2013.01.019

Cited by 27 publications

(20 citation statements)

References 54 publications

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“…Moreover, the ultrasound does not form secondary foci similarly to a toroidal transducer. 28) In this study, this method with the vortex mode number m of 5 was applied to a 128-channel array transducer (Japan Probe). A schematic of the 128-channel array transducer with a phase delay and a normalized pressure field, and numerically simulated by linear approximation by Rayleigh-Sommerfeld integral is shown in Fig.…”

Section: Sector Vortex Array Methodsmentioning

confidence: 99%

Effect of annular focusing of ultrasound on rate of stone erosion using cavitation bubbles

Yura

Lafond

Yoshizawa

et al. 2018

Jpn. J. Appl. Phys.

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Shock wave lithotripsy has been one of the first-line treatments to fragment kidney stones. One disadvantage of this method is that some residual stone fragments can be too large to pass through the ureters. Stone fragments can be made small enough by ultrasonically induced cavitation erosion, but the erosion rate, with conventional single-spot focusing, tends to be low owing to ultrasound attenuation by excessively generated cavitation bubbles upstream of the stone surface. Sector vortex annular focusing can generate cavitation bubbles widely and thinly. We propose exposure sequences utilizing this focusing scheme and investigated their effect on erosion rate using a stone model. Sector vortex annular focusing showed an erosion rate significantly higher than that of single-spot focusing. Among them, switching between the two focusing schemes provided the highest rate, higher than the mathematical sum of those of the two schemes, and even higher than that of sector vortex focusing at the same pulse repetition.

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Section: Sector Vortex Array Methodsmentioning

confidence: 99%

Effect of annular focusing of ultrasound on rate of stone erosion using cavitation bubbles

Yura

Lafond

Yoshizawa

et al. 2018

Jpn. J. Appl. Phys.

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“…For example, in RFA (Refs. 1 and 12) or bulk ultrasound ablation, 68,69 which thermal lesioning occurs over a relatively broad region, determined by the geometry and other properties of the ablation probes employed. Appropriate probes and exposure conditions are chosen based on the targeted size of the ablation zone, which typically ranges between 1 and 5 cm in diameter.…”

Section: B Effect Of Correlation Window Sizementioning

confidence: 99%

Analysis of tissue changes, measurement system effects, and motion artifacts in echo decorrelation imaging

Hooi

Nagle

Subramanian

et al. 2015

The Journal of the Acoustical Society of America

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Echo decorrelation imaging, a method for mapping ablation-induced ultrasound echo changes, is analyzed. Local echo decorrelation is shown to approximate the decoherence spectrum of tissue reflectivity. Effects of the ultrasound measurement system, echo signal windowing, electronic noise, and tissue motion on echo decorrelation images are determined theoretically, leading to a method for reduction of motion and noise artifacts. Theoretical analysis is validated by simulations and experiments. Simulated decoherence of the scattering medium was recovered with root-mean-square error less than 10% with accuracy dependent on the correlation window size. Motion-induced decorrelation measured in an ex vivo pubovisceral muscle model showed similar trends to theoretical motion-induced decorrelation for a 2.1 MHz curvilinear array with decorrelation approaching unity for 3-4 mm elevational displacement or 1-1.6 mm range displacement. For in vivo imaging of porcine liver by a 7 MHz linear array, theoretical decorrelation computed using image-based motion estimates correlated significantly with measured decorrelation (r = 0.931, N = 10). Echo decorrelation artifacts incurred during in vivo radiofrequency ablation in the same porcine liver were effectively compensated based on the theoretical echo decorrelation model and measured pre-treatment decorrelation. These results demonstrate the potential of echo decorrelation imaging for quantification of heat-induced changes to the scattering tissue medium during thermal ablation.

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“…While changes in Q with f have been considered previously, to the authors' knowledge, this study presents a novel attempt to include the effects of the changing focal volume. Moreover, this study includes targets as far as 150 mm deep in tissue which is significantly deeper than what has been explored in most other studies, 40,47,53 though not inordinately deep if one considers the target and the increasing prevalence of obesity. 68 When focus volume is considered and deeper targets are sought, it appears that the optimal frequency from an efficiency perspective is between 500 and 750 kHz: lower for greater depths and higher attenuation coefficients and higher for lesser depths and lower attenuation environments.…”

Section: Discussionmentioning

confidence: 99%

“…Nonspherically curved transducers have been proposed: a toroidal transducer has been shown to produce an enlarged focal volume. 40 However, for largevolume ablations, this is insufficient and either the transducer must be steered manually to focus at many points, 38 or an electronically steered phased array can be employed. The ExAblate 2000 and 2100 and Philips Sonalleve systems use a hybrid solution to enlarge the treatment volume: numerous phased array elements [ExAblate: 208; 13 Sonalleve: 256 (Ref.…”

Section: Introductionmentioning

confidence: 99%

Frequency considerations for deep ablation with high‐intensity focused ultrasound: A simulation study

Ellens

Hynynen

2015

Medical Physics

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Electronic Beam Steering Used with a Toroidal HIFU Transducer Substantially Increases the Coagulated Volume

Cited by 27 publications

References 54 publications

Effect of annular focusing of ultrasound on rate of stone erosion using cavitation bubbles

Effect of annular focusing of ultrasound on rate of stone erosion using cavitation bubbles

Analysis of tissue changes, measurement system effects, and motion artifacts in echo decorrelation imaging

Frequency considerations for deep ablation with high‐intensity focused ultrasound: A simulation study

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