Fast passive cavitation mapping with angular spectrum approach

Abstract

Several emerging focused ultrasound (FUS) therapies harness the effects produced by acoustic cavitation. Passive acoustic mapping (PAM) can be used to characterize and visualize the microbubble oscillations and guide these procedures. Here, we propose and demonstrate that angular spectrum approach (ASA) can be used to back-project the passively recorded, by an array of receivers, diverging pressure waves generated from oscillating microbubbles to perform rapid PAM reconstructions. In the present work, acoustic cavitation is studied transcranially in non-human primates using an integrated ultrasound and MRI-guided clinical FUS system. In addition, from CT datasets, we also extract the skull acoustic properties and use them as inputs to numerical simulations. Using both the simulated and experimental data we validate the use of ASA to perform PAM reconstructions and compare its performance to time domain PAM. The experimental data demonstrate that ASA can be used to reconstruct frequency-selective PAM. Numerical simulations suggest that ASA reconstructions have the same resolution with time domain PAM, while the reconstruction time was 72 times faster for the same image dimensions. These results suggest that ASA-based PAM reconstructions can provide real-time passive cavitation mapping and, by extension, control over FUS procedures.