—Passive acoustic mapping (PAM) is an algorithm that reconstructs the location of acoustic sources
using an array of receivers. This technique can monitor therapeutic ultrasound procedures to confirm the spatial distribution and amount of microbubble activity induced. Current
PAM algorithms have an excellentlateral resolution but have
a poor axial resolution, making it difficult to distinguish
acoustic sources within the ultrasound beams. With recent
studies demonstrating that short-length and low-pressure
pulses—acoustic wavelets—have the therapeutic function,
we hypothesizedthat the axial resolution could be improved
with a quasi-pulse-echo approach and that the resolution
improvement would depend on the wavelet’s pulse length.
This article describes an algorithm that resolves acoustic
sources axially using time of flight and laterally using delayand-sum beamforming, which we named axial temporal
position PAM (ATP-PAM). The algorithm accommodates a
rapid short pulse (RaSP) sequence that can safely deliver
drugs across the blood–brain barrier. We developed our
algorithm with simulations (k-wave) and in vitro experiments for one-, two-, and five-cycle pulses, comparing
our resolution against that of two current PAM algorithms.
We then tested ATP-PAM in vivo and evaluated whether the
reconstructed acoustic sources mapped to drug delivery