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Magnetic Resonance-Guided High-Intensity Focused Ultrasound for Localized Ablation of Head and Neck Tissue Structures: A Feasibility Study in An Animal Model

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A Partanen

A Partanen1*, N Ellens2 , S Noureldine2 , E Burdette3 , R Tufano2 , K Farahani4 , (1) Philips Healthcare, Andover, Massachusets, (2) Johns Hopkins University School of Medicine, Baltimore, Maryland, (3) Acoustic MedSystems Inc., Savoy, IL, (4) National Cancer Institute, Bethesda, MD


WE-EF-BRA-12 (Wednesday, July 15, 2015) 1:45 PM - 3:45 PM Room: Ballroom A

Purpose: High-intensity focused ultrasound (HIFU) ablation is feasible in the head and neck [1]. This study aims to expand upon these findings to assess the feasibility of treatment planning and monitoring via magnetic resonance imaging (MRI) guidance using a clinical MR-guided HIFU platform.

Methods: Two 31 kg pigs were anaesthetized, shaved, and positioned prone on the HIFU table (Sonalleve, Philips Healthcare, Vantaa, Finland). The necks were acoustically coupled to the integrated transducer using gel pads and degassed water. MR imaging verified acoustic coupling and facilitated target selection in the thyroid and thymus. Targets were thermally ablated with 130-200 W of acoustic power over a period of 16 s at a frequency of 1.2 MHz while being monitored through real-time, multi-planar MR-thermometry. Contrast-enhanced MR imaging was used to assess treatment efficacy. Post-treatment, animals were euthanized and sonicated tissues were harvested for histology assessment.

Results: MR-thermometry, post-contrast-imaging, and gross pathology demonstrated that the system was capable of causing localized thermal ablation in both the thyroid and the thymus without damaging the aerodigestive tract. In one animal, superficial bruising was observed in the ultrasound beam path. Otherwise, there were no adverse events. Analysis of the tissue histology found regions of damage consistent with acute thermal injury at the targeted locations.

Conclusion: It is feasible to use a clinical MR-guided HIFU platform for extracorporeal ablation of porcine head and neck tissues. MR guidance and thermometry are sufficient to target and monitor treatment in the thyroid region, despite the presence of the inhomogeneous aerodigestive tract. Further study is necessary to assess efficacy and survival using a tumor model, and to examine what modifications should be made to the transducer positioning system and associated patient positioning aids to adapt it for clinical head and neck targets.

[1] Esnault et al. (2011). Thyroid, 21(9), 965–973.

Funding Support, Disclosures, and Conflict of Interest: Funding support provided by Philips Healthcare. Ari Partanen is a paid employee of Philips Healthcare.

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