The 176th Meeting of the Acoustical Society of America (ASA) was held November 5–9, 2018, in Victoria, British Columbia, Canada. With an overall mission to generate, disseminate, and promote the knowledge and practical applications of acoustics, the meeting included several presentations of interest to the focused ultrasound community. Researchers from the Focused Ultrasound Foundation were invited to present their recent simulation study that developed and validated algorithms for how ultrasound propagates through the skull. Additional topics in the program included blood—spinal cord barrier opening, blood-brain barrier opening, droplet vaporization for mechanical brain tissue ablation, additional simulation work, and much more.
Blood–Spinal Cord Barrier (BSCB) Opening. Several papers from the University of Toronto/Sunnybrook Research Institute addressed BSCB opening. They described preclinical work, modeling, and the design of a transducer prototype for BSCB opening within human vertebrae. Their technique looks to be effective in preclinical experiments, and further technological development is ongoing to scale the transducers for human use.
Blood-Brain Barrier (BBB) Opening. Dr. Mark Borden (Boulder) presented data suggesting that the gas volume of injected microbubbles is the unifying parameter in microbubble dosing for BBB opening. O. Vince (PhD student with Dr. Eleanor Stride, Oxford, UK) presented preclinical work on the use of targeted magnetic nanodroplets for BBB opening. This is the first proof of concept study, and her preclinical study is ongoing.
Droplet Vaporization for Mechanical Brain Tissue Ablation. Drs. Tyrone Porter (Boston University) and Nathan McDannold (Harvard/Brigham and Women’s) are investigating mechanical (cavitation/non-thermal) ablation of brain tumors with phase-shift nanodroplets. This preclinical work is centered on developing safe and effective treatment regimens. It uses low frequency focused ultrasound that is close to the 220kHz range of the ExAblate system.
Simulation of Acoustic Propagation through Bone. L. Richards (PhD student with Dr. Robin Cleveland, Oxford, UK) presented neuromodulation simulations using k-waves to simulate propagation through human skull from a single element focused transducer. Experiments on volunteers are ongoing. Researchers at the University of Toronto presented a ray tracing method to simulate propagation through human vertebrae with phased array. The group from the Focused Ultrasound Foundation shared an invited presentation on their work simulating propagation through skull using experimental data to validate the algorithms.
Meeting report submitted by Frédéric Padilla, PhD, Foundation Research Fellow.
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1aBA10. Observation of acoustic fountain generation by diagnostic ultrasound shear wave elastography.
1pBA3. Dual-mode capacitive micromachined ultrasonic transducer arrays for high intensity focused ultrasound and imaging.
1pBA4. Various approaches for designing phased arrays for high intensity focused ultrasound therapies: From sparse to fully-populated configurations.
1pBA10. Development of a freely available simulator with graphical interface for modeling nonlinear focused ultrasound fields with shocks.
1pBA11. Nonlinear ultrasound fields generated by a 256-element spiral array for boiling histotripsy.
2aBAa8. Ultrasonic evaluation of anisotropic structure of swine skull.
2aBAa10. Simulation of ultrasound propagation through human skull: Experimental validation and application to treatment planning.
2aBAa11. Implementation of a dynamic ray tracing method in CIVA HealthCare HIFU simulation platform—Application to the propagation in inhomogeneous and heterogeneous tissues.
2aBAa12. A ray acoustics-based simulation for predicting trans-vertebral ultrasound propagation: Simulation accuracy.
2aBAb3. Cytomechanical perturbations induced by pulsed ultrasound and acoustic cavitation.
2pBAa2. Acoustic radiation force acting on a spherical scatterer in water: Measurements and simulation.
2pBAa3. Generation of guided waves during burst wave lithotripsy as a mechanism of stone fracture.
3aBAb1. Microbubble gas volume: A unifying dose parameter in blood-brain barrier disruption by focused ultrasound.
3aBAb2. Persistent Pests: The role of gas diffusion in histotripsy bubble longevity.
3aBAb3. Effect of high intensity focused ultrasound transducer F-number and waveform non-linearity on inertial cavitation activity.
3aBAb9. Non-linear acoustic emissions from therapeutically driven microbubbles.
3pBAa4. Real-time imaging-guided microbubble mediated high intensity focused ultrasound heating in an ex-vivo machine-perfused pig liver.
4aBA8. Influence of surfactant encapsulation on the acoustic droplet vaporization.
4aBA9. Phase shift nanoemulsions facilitated focused ultrasound nonthermal ablation in mice brain.
4pBA1. Focusing ultrasound into the kidney using 3D patient models.
4pBA3. Analysis of a dual aperture approach and standing wave suppression pulse sequences for controlled transvertebral focused ultrasound delivery in ex vivo human thoracic vertebrae.
4pBA4. Passive elastography monitoring of a high intensity ultrasound treatment: A study of feasibility in in vitro liver.