AN IN SILICO STUDY OF LOW-INTENSITY FOCUSED ULTRASOUND DISPLACEMENT MAPPING WITH A 220 KHZ CLINICAL PHASED-ARRAY...

This study aimed to numerically investigate spatio-temporal displacement and pressure-field characteristics during blood-brain barrier (BBB) opening procedures. Magnetic resonance acoustic radiation force impulse (MR-ARFI) imaging use with a clinical 220 kHz system for microbubble-mediated BBB opening is unreported. A simulation environment was developed to determine the feasibility of MR-ARFI imaging for targeted treatment. A clinical focused ultrasound transducer system was modeled, using a virtual tissue-segmented skull model. Acoustic power was adjusted to determine the changes in pressure and displacement within the skull cavity. The focal shape was adjusted with holography to observe the changes in displacement. Calculations and simulations suggested displacement imaging might be feasible for pretreatment targeting without microbubbles at a mechanical index near 1.9. Computations showed at a constant mechanical index, displacement increased with focal spot diameter, focal spot length, higher frequency, and in white matter compared to gray matter.