INSILICOSTUDYOFLOW-FREQUENCY TRANSCRANIAL ULTRASOUNDFIELDS IN ACUTE ISCHEMIC STROKE PATIENTS

Ultrasound in the sub-megahertz range enhances thrombolysis and may be applied transcranially to ischemic strokepatients.Theconsistencyoftranscranialinsonificationneedstobeevaluated.Acousticandthermal simulations based on computed-tomography (CT) scans of 20 patients were performed. An unfocused 120-kHz transducer allowed homogeneous insonification of the thrombus, and positioning based on external landmarks performed similarly to an optimized placement based on CT data. With a weakly focused 500-kHz transducer, the landmark-based positioning underperformed. The predicted inter-patient variation ofin situ acoustic pressure was similar withboththe 120 and 500-kHztransducers for the optimized placement (18.0-26.4% relative standard deviation). The simulated maximum acoustic pressure in intervening tissues was 2.6 ± 0.6 and 2.0 ± 0.7 times the pressure in the thrombus for the 120-kHz and 500-kHz transducers, respectively. A 1 W/cm 2 insonification of the thrombus caused a 3.8 ± 2.2 � C increase in the bone for the 120-kHz transducer, and a 13.4 ± 3.3 � C increase for the 500-kHz transducer. Contralateral local maxima up to 1.1 times the pressure amplitude in the targeted zone were predicted for the 120-kHz transducer. We established two transducer placement approaches,one based on analysis of a head CT and the other using simple external, visible landmarks. Both approaches allowed consistent insoni- fication of the thrombus. (E-mail: Christy.Holland@uc.edu) 2014 World Federation for Ultrasound in Med- icine & Biology.