Transcranial acoustic imaging for real-time control of ultrasound-mediated blood-brain barrier opening using a clinical-scale prototype system

Abstract

Multichannel beamforming of passively detected ultrasound (US)-stimulated acoustic emissions is a promising method for guiding cavitation-mediated therapies. In the context of brain applications, our group and others have previously demonstrated the use of conventional beamforming techniques to transcranially map cavitation activity during microbubble (MB)-mediated blood-brain barrier (BBB) opening. MB activity can be mapped at pressure levels below the BBB opening threshold, allowing target confirmation prior to therapy delivery. By including skull-specific phase and amplitude corrections in the reconstruction process, the aberrating effects of the cranial bone can be compensated for to improve image quality. Recently, we have designed, fabricated, and characterized multi-frequency, transmit/receive, sparse hemispherical phased arrays for MB-mediated brain therapy and simultaneous cavitation mapping [Deng et al. , Phys. Med. Biol. 61, 8476-8501 (2016)]. This talk will review our progress to date in using these prototype systems to exploit the spatial information obtained from receive beamforming to actively modulate the therapeutic exposures during US-induced BBB opening, following our previously developed single-element internal calibration approach [O’Reilly & Hynynen, Radiology 263, 96-106 (2012)]. We anticipate that this technique will improve the safety and efficacy of MB-mediated BBB opening, as well as other future non-thermal US brain treatments such as cavitation-enhanced ablation, sonothrombolysis, and histotripsy.