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Gilles Thomas

Research Scientist/Engineer - Senior

Email

gthomas@apl.washington.edu

Phone

206-221-4590

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

Advancing boiling histotripsy dose in ex vivo and in vivo renal tissues via quantitative histological analysis and shear wave elastography

Ponomarchuk, E., G. Thomas, M. Song, Y.-N. Wang, S. Totten, G. Schade, J. Thiel, M. Bruce, V. Khokhlova, and T. Khokhlova, "Advancing boiling histotripsy dose in ex vivo and in vivo renal tissues via quantitative histological analysis and shear wave elastography," Ultrasound Med. Biol., 50, 1936-1944, doi:10.1016/j.ultrasmedbio.2024.08.022, 2024.

More Info

1 Dec 2024

Objective
In the context of developing boiling histotripsy (BH) as a potential clinical approach for non-invasive mechanical ablation of kidney tumors, the concept of BH dose (BHD) was quantitatively investigated in porcine and canine kidney models in vivo and ex vivo.

Methods
Volumetric lesions were produced in renal tissue using a 1.5-MHz 256-element HIFU-array with various pulsing protocols: pulse duration tp = 1–10 ms, number of pulses per point ppp = 1–15. Two BHD metrics were evaluated: BHD1 = ppp, BHD2 = tp × ppp. Quantitative assessment of lesion completeness was performed by their histological analysis and assignment of damage score to different renal compartments (i.e., cortex, medulla, and sinus). Shear wave elastography (SWE) was used to measure the Young's modulus of renal compartments in vivo vs ex vivo, and before vs after BH treatments.

Results
In vivo tissue required lower BH doses to achieve identical degree of fractionation as compared to ex vivo. Renal cortex (homogeneous, low in collagen) was equal or higher in stiffness than medulla (anisotropic, collagenous), 5.8–12.2 kPa vs 4.7–9.6 kPa, but required lower BH doses to be fully fractionated. Renal sinus (fatty, irregular, with abundant collagenous structures) was significantly softer ex vivo vs in vivo, 4.9–5.1 kPa vs 9.7–15.2 kPa, but was barely damaged in either case with any tested BH protocols. BHD1 was shown to be relevant for planning the treatment of renal cortex (sufficient BHD1 = 5 pulses in vivo and 10 pulses ex vivo), while none of the tested doses resulted in complete fractionation of medulla or sinus. Post-treatment SWE imaging revealed reduction of tissue stiffness ex vivo by 27–58%, increasing with the applied dose, and complete absence of shear waves within in vivo lesions, both indicative of tissue liquefaction.

Conclusion
The results imply that tissue resistance to mechanical fractionation, and hence required BH dose, are not solely determined by tissue stiffness but also depend on its composition and structural arrangement, as well as presence of perfusion. The SWE-derived reduction of tissue stiffness with increasing BH doses correlated with tissue damage score, indicating potential of SWE for post-treatment confirmation of BH lesion completeness.

Histotripsy-induced bactericidal activity correlates to size of cavitation cloud in vitro

Ambekar, P.A., Y.-N. Wang, T.D. Khokhlova, G.P.L. Thomas, P.B. Rosnitskiy, K. Contreras, D.F. Leotta, A.D. Maxwell, M. Bruce, S. Pierson, S. Totten, Y.N. Kumar, J. Thiel, K.T. Chan, W.C. Liles, E.P. Dellinger, A. Adedipe, W.L. Monsky, and T.J. Matula, "Histotripsy-induced bactericidal activity correlates to size of cavitation cloud in vitro," IEEE Trans. Ultrason. Ferroelectr. Freq. Control, 71, 1868-1878, doi:10.1109/TUFFC.2024.3476438, 2024.

More Info

9 Oct 2024

Large abscesses are walled-off collections of pus and bacteria that often do not respond to antibiotic therapy. Standard of care involves percutaneous placement of indwelling catheter(s) for drainage, a long and uncomfortable process with high rehospitalization rates. The long-term goal of this work is to develop therapeutic ultrasound approaches to eradicate bacteria within abscesses as a noninvasive therapeutic alternative. Inertial cavitation induced by short pulses of focused ultrasound (histotripsy) is known to generate lethal mechanical damage in bacteria. Prior studies with Escherichia coli (E. coli) in suspension demonstrated that bactericidal effects increase with increasing peak negative amplitude, treatment time, and duty cycle. The current study investigated correlates of bactericidal activity with histotripsy cavitation cloud size. Histotripsy was applied to E. coli suspensions in 10-mL sample vials at 810 kHz, 1.2 MHz, or 3.25 MHz for 40 min. The cavitation activity in the sample vials was separately observed with high-speed photography. The cavitation cloud area was quantified from those images. A linear relationship was observed between bacterial inactivation and cavitation cloud size ( R2 = 0.98 ), regardless of the acoustic parameters (specifically frequency, pulse duration, and power) used to produce the cloud.

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.

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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.

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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