Passive acoustic mapping using optimal beamforming for real-time monitoring of ultrasound therapy

In ultrasound therapy, passive acoustic mapping (PAM) has been shown to be an effective method for imaging the acoustic emissions generated during treatment providing the potential for real-time therapy monitoring. In both high intensity ultrasound (HIFU) ablative surgery and targeted drug delivery, imaging artefacts at higher amplitude exposure conditions have been observed which make the localization and dosimetry of therapeutically relevant cavitation activity a challenge. Due to these artefacts, correlating drug release or lesion volumes to the PAMs is hindered for many exposures. It is proposed that incorporating optimal beamforming techniques into the PAM framework can reduce and remove these artefacts allowing determination of the extent of cavitation activity during ultrasound therapy. Additionally, optimal beaforming is found to yield improved resolution, good interference suppression, and robustness against steering vector errors. A description of the origin of the artefacts as well as reduction of them by implementing optimal beamforming within PAM will be demonstrated in the context of targeted drug delivery.