• Sagi Harnof, Arik Hananel, Zion Zilby, Iris Kulbatski, Moshe Hadani, and Neal Kassell.
• Department of Neurosurgery, Sheba Medical Center, Tel-Hashomer, Israel.
• Int J Stroke. 2014 Jan 1;9(1):40-7.

BackgroundIntracranial hemorrhage has a mortality rate of up to 40-60% due to the lack of effective treatment. Magnetic resonance-guided focused ultrasound may offer a breakthrough noninvasive technology, by allowing accurate delivery of focused ultrasound, under the guidance of real-time magnetic resonance imaging.AimThe purpose of the current study was to optimize the acoustic parameters of magnetic resonance-guided focused ultrasound for effective clot liquefaction, in order to evaluate the feasibility of magnetic resonance-guided focused ultrasound for thrombolysis.MethodsBody (1·1 MHz) and brain (220 kHz) magnetic resonance-guided focused ultrasound systems (InSightec Ltd, Tirat Carmel, Israel) were used to treat tube-like (4 cc), round (10 cc), and bulk (300 cc) porcine blood clots in vitro, using burst sonications of one-second to five-seconds, a duty cycle of 5-50%, and peak acoustic powers between 600 and 1200 W. Liquefied volumes were measured as hyperintense regions on T2-weighted magnetic resonance images for body unit sonications (duration of one-second, duty cycle of 10%, and power of 500-1200 W). Liquefaction efficiency was calculated for brain unit sonications (duration of one-second, duty cycle of 10%, power of 600 W, and burst length between 0·1 ms and 100 ms).ResultsLiquified lesion volume increased as power was raised, without a thermal rise. For brain unit sonications, a power setting of 600 W and ultrashort sonications (burst length between 0·1 and 1·0 ms) resulted in liquefaction efficacy above 50%, while longer burst duration yielded lower efficacy.ConclusionsThese results demonstrate the feasibility of obtaining reproducible, rapid, efficient, and accurate blood clot lysis using the magnetic resonance-guided focused ultrasound system. Further in vivo studies are needed to validate the feasibility of magnetic resonance-guided focused ultrasound as a treatment modality for intracranial hemorrhage.© 2013 The Authors. International Journal of Stroke © 2013 World Stroke Organization.

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