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Gilles Thomas

Postdoctoral Scholar

Email

gthomas@apl.washington.edu

Phone

206-221-5703

Education

M.S. General Engineering, Ecole Centrale de Nantes, 2014

M.S. Mechatronic Engineering, Universidade de Sao Paulo, 2014

M.S. Mechatronic Engineering, Universidade de Sao Paulo, 2015

Ph.D. Biomedical Engineering, Universite Lyon, 2019

Publications

2000-present and while at APL-UW

Development of an automated ultrasound signal indicator of lung interstitial syndrome

Khokhlova, T.D., G.P. Thomas, J. Hall, K. Steinbock, J. Thiel, B.W. Cunitz, M.R. Bailey, L. Anderson, R. Kessler, M.K. Hall, and A.A. Adedipe, "Development of an automated ultrasound signal indicator of lung interstitial syndrome," J. Ultrasound Med., EOR, doi:10.1002/jum.16383, 2023.

More Info

5 Dec 2023

The number and distribution of lung ultrasound (LUS) imaging artifacts termed B-lines correlate with the presence of acute lung disease such as infection, acute respiratory distress syndrome (ARDS), and pulmonary edema. Detection and interpretation of B-lines require dedicated training and is machine and operator-dependent. The goal of this study was to identify radio frequency (RF) signal features associated with B-lines in a cohort of patients with cardiogenic pulmonary edema. A quantitative signal indicator could then be used in a single-element, non-imaging, wearable, automated lung ultrasound sensor (LUSS) for continuous hands-free monitoring of lung fluid.

Enhancement of boiling histotripsy by steering the focus axially during the pulse delivery

Thomas, G.P.L., T.D. Khokhlova, O.A. Sapozhnikov, and V.A. Khokhlova, "Enhancement of boiling histotripsy by steering the focus axially during the pulse delivery," IEEE Trans. Ultrason. Ferroelectr. Freq. Control, 70, 865-875, doi:10.1109/TUFFC.2023.3286759, 2023.

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1 Aug 2023

Boiling histotripsy (BH) is a pulsed high-intensity focused ultrasound (HIFU) method relying on the generation of high-amplitude shocks at the focus, localized enhanced shock-wave heating, and bubble activity driven by shocks to induce tissue liquefaction. BH uses sequences of 1–20 ms long pulses with shock fronts of over 60 MPa amplitude, initiates boiling at the focus of the HIFU transducer within each pulse, and the remainder shocks of the pulse then interact with the boiling vapor cavities. One effect of this interaction is the creation of a prefocal bubble cloud due to reflection of shocks from the initially generated mm-sized cavities: the shocks are inverted when reflected from a pressure-release cavity wall resulting in sufficient negative pressure to reach intrinsic cavitation threshold in front of the cavity. Secondary clouds then form due to shock-wave scattering from the first one. Formation of such prefocal bubble clouds has been known as one of the mechanisms of tissue liquefaction in BH. Here, a methodology is proposed to enlarge the axial dimension of this bubble cloud by steering the HIFU focus toward the transducer after the initiation of boiling until the end of each BH pulse and thus to accelerate treatment. A BH system comprising a 1.5 MHz 256-element phased array connected to a Verasonics V1 system was used. High-speed photography of BH sonications in transparent gels was performed to observe the extension of the bubble cloud resulting from shock reflections and scattering. Volumetric BH lesions were then generated in ex vivo tissue using the proposed approach. Results showed up to almost threefold increase of the tissue ablation rate with axial focus steering during the BH pulse delivery compared to standard BH.

Quantitative assessment of boiling histotripsy progression based on color Doppler measurements

Song, M.H., G.P.L. Thomas, V.A. Khokhlova, O.A. Sapozhnikov, M.R. Bailey, A.D. Maxwell, P.V. Yuldashev, and T.D. Khokhlova, "Quantitative assessment of boiling histotripsy progression based on color Doppler measurements," IEEE Trans. Ultrason. Ferroelectr. Freq. Control, 69, 3255-3269, doi:10.1109/TUFFC.2022.3212266, 2022.

More Info

1 Dec 2022

Boiling histotripsy (BH) is a mechanical tissue liquefaction method that uses sequences of millisecond-long high intensity focused ultrasound (HIFU) pulses with shock fronts. The BH treatment generates bubbles that move within the sonicated volume due to acoustic radiation force. Since the velocity of the bubbles and tissue debris is expected to depend on the lesion size and liquefaction completeness, it could provide a quantitative metric of the treatment progression. In this study, the motion of bubble remnants and tissue debris immediately following BH pulses was investigated using high-pulse repetition frequency (PRF) plane-wave color Doppler ultrasound in ex vivo myocardium tissue. A 256-element 1.5 MHz spiral HIFU array with a coaxially integrated ultrasound imaging probe (ATL P4-2) produced 10 ms BH pulses to form volumetric lesions with electronic beam steering. Prior to performing volumetric BH treatments, the motion of intact myocardium tissue and anticoagulated bovine blood following isolated BH pulses was assessed as two limiting cases. In the liquid blood the velocity of BH-induced streaming at the focus reached over 200 cm/s, whereas the intact tissue was observed to move toward the HIFU array consistent with elastic rebound of tissue. Over the course of volumetric BH treatments tissue motion at the focus locations was dependent on the axial size of the forming lesion relative to the corresponding size of the HIFU focal area. For axially small lesions, the maximum velocity after the BH pulse was directed toward the HIFU transducer and monotonically increased over time from about 20–100 cm/s as liquefaction progressed, then saturated when tissue was fully liquefied. For larger lesions obtained by merging multiple smaller lesions in the axial direction, the high-speed streaming away from the HIFU transducer was observed at the point of full liquefaction. Based on these observations, the maximum directional velocity and its location along the HIFU propagation axis were proposed and evaluated as candidate metrics of BH treatment completeness.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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