Targeting Accuracy of Transcranial Power Cavitation Imaging for Blood-Brain Barrier Opening Using a Theranostic Phased Array

Transcranial ultrasound-based monitoring of focused ultrasound (FUS)-mediated blood-brain barrier (BBB) opening is a challenge due to signal attenuation, phase aberration and focal distortion resulting from acoustic wave propagation through the skull. However, transcranial passive cavitation mapping is critical for ensuring noninvasive, safe, and consistent treatment. Power cavitation imaging using a diagnostic phased array synchronized with a FUS-induced BBB opening protocol poses one solution for transcranial cavitation mapping given the minimal focal shift resulting from transcranial ultrasound transmission. 1.94 mm and 1.01 mm average axial and lateral focal shifts, respectively, through primate skulls were observed during in vitro experiments and were recapitulated consistently by simulations. Average axial and lateral shifts in the apparent location of a microbubble flow channel detected via transcranial power cavitation imaging of 1.13 mm and 0.50 mm, respectively, agreed well with simulation results and results of other studies demonstrating registration errors after transcranial imaging of a microbubble flow channel.