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Design of a Low-Power, Minimally Invasive High Intensity Focused Ultrasound Device for Ablative Applications in Neuro-Oncology: A Simulation Study

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X Zhang

X Zhang1*, N Ellens2 , M Belzberg3 , P Miller3 , A Cohen3 , H Brem3,J Siewerdsen1,3 , A Manbachi1,3 , (1) Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, (2) Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, (3) Department of Neurosurgery, Johns Hopkins University School of Medicine


TU-D-708-3 (Tuesday, August 1, 2017) 11:00 AM - 12:15 PM Room: 708

Purpose: We propose an innovative high intensity focused ultrasound (HIFU) device that can be inserted into a brain ventricle via a common, minimally-invasive neurosurgical procedure, thereby circumventing the skull. Transcranial HIFU is a promising technique for treating brain tumors via precise thermal ablation but its noninvasive characteristic requires ultrasound propagation through highly attenuating skull bone. Our alternative design permits higher energy efficiency than transcranial applications while remaining precision, further expanding the reach of HIFU therapy for neuro-oncology applications.

Methods: A simulation study was conducted to evaluate the achievable lesioning efficiency and power usage of a flexible transducer phased array with a surface area of 20 mm x 8 mm. A heterogeneous medium volume containing cerebrospinal fluid and brain tissue was simulated, wherein the target was 3 cm away from the transducer surface. The array was modelled at frequencies of 1.5 to 3 MHz and focused electronically and mechanically (radii of curvature of 1.25, 2.5, 5 cm and flat). Corresponding temperature maps were generated using Penne’s bioheat transfer equation. Lesion dimensions and required power levels were derived based on Sapareto and Dewey’s thermal dose function for reaching peak temperature of 65 °C with sonication time of 15 s and a cooling period of 90 s.

Results: The lesion can possess a depth of field of ~1 cm and a width of ~0.15 cm with a curvature of 5 cm and a frequency of 3 MHz. This is achievable with a power of 11.8 W, which is two orders of magnitude lower than the power used for transcranial approach.

Conclusion: The proposed intracranial HIFU device overcomes the attenuation challenge associated with the transcranial therapy by leveraging a common neurosurgical intervention approach and has the potential to provide fine ablation volume control at low power through combination of acoustic frequency and transducer curvature.

Funding Support, Disclosures, and Conflict of Interest: Johns Hopkins Translational Coulter Funding, "Minimally Invasive, Focused Ultrasound for Brain Surgeries" (account No: 90069768)

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