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Integration of Interstitial High Intensity Therapeutic Ultrasound Applicators On a Clinical MRI-Guided High Intensity Focused Ultrasound Treatment Planning Software Platform

N Ellens

N Ellens1*, A Partanen2 , G Ghoshal3 , E Burdette3 , K Farahani4 , (1) Johns Hopkins University, Baltimore, Maryland, (2) Philips Healthcare, Andover, Massachusets, (3) Acoustic MedSystems Inc., Savoy, IL, (4) National Cancer Institute, Bethesda, MD


SU-E-J-4 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Interstitial high intensity therapeutic ultrasound (HITU) applicators can be used to ablate tissue percutaneously, allowing for minimally-invasive treatment without ionizing radiation [1,2]. The purpose of this study was to evaluate the feasibility and usability of combining multi-element interstitial HITU applicators with a clinical magnetic resonance imaging (MRI)-guided focused ultrasound software platform.

Methods: The Sonalleve software platform (Philips Healthcare, Vantaa, Finland) combines anatomical MRI for target selection and multi-planar MRI thermometry to provide real-time temperature information. The MRI-compatible interstitial US applicators (Acoustic MedSystems, Savoy, IL, USA) had 1-4 cylindrical US elements, each 1 cm long with either 180° or 360° of active surface. Each applicator (4 Fr diameter, enclosed within a 13 Fr flexible catheter) was inserted into a tissue-mimicking agar-silica phantom. Degassed water was circulated around the transducers for cooling and coupling. Based on the location of the applicator, a virtual transducer overlay was added to the software to assist targeting and to allow automatic thermometry slice placement. The phantom was sonicated at 7 MHz for 5 minutes with 6-8 W of acoustic power for each element. MR thermometry data were collected during and after sonication.

Results: Preliminary testing indicated that the applicator location could be identified in the planning images and the transducer locations predicted within 1 mm accuracy using the overlay. Ablation zones (thermal dose ≥ 240 CEM43) for 2 active, adjacent US elements ranged from 18 mm x 24 mm (width x length) to 25 mm x 25 mm for the 6 W and 8 W sonications, respectively.

Conclusion: The combination of interstitial HITU applicators and this software platform holds promise for novel approaches in minimally-invasive MRI-guided therapy, especially when bony structures or air-filled cavities may preclude extracorporeal HIFU.

[1] Diederich et al. IEEE UFFFC 46.5 (1999): 1218.
[2] Chopra et al. PMB 50.21 (2005): 4957.

Funding Support, Disclosures, and Conflict of Interest: Funding support was provided by Philips Healthcare and in-kind support from Acoustic MedSystems Inc. Ari Partanen is a paid employee of Philips Healthcare. Goutam Ghoshal and Everette Clif Burdette are paid employees of Acoustic MedSystems Inc.

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