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 excellent lateral 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 hypothesized that 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 delay-and-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 within the brain. In simulations and in vitro , ATP-PAM had an improved resolution for all pulse lengths tested. In vivo , experiments in mice indicated that ATP-PAM could be used to target and monitor drug delivery into the brain. With acoustic wavelets and time of flight, ATP-PAM can locate acoustic sources with a vastly improved spatial resolution.

中文翻译：

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用治疗性小波成像–当到达时间与延迟和总和结合时，短脉冲可实现声波定位

无源声学映射（PAM）是一种使用接收器阵列重建声源位置的算法。此技术可以监视治疗性超声程序，以确认空间分布和诱导的微气泡活动量。当前的PAM算法具有出色的横向分辨率，但轴向分辨率却很差，因此很难区分超声束内的声源。最近的研究表明，短脉冲和低压脉冲（声波小波）具有治疗功能，我们假设准脉冲回波方法可以改善轴向分辨率，而分辨率的提高将取决于小波的脉冲长度。本文介绍了一种算法，该算法使用飞行时间轴向解析声源，并使用延迟和求和波束成形横向解析声源，我们将其称为轴向时间位置PAM（ATP-PAM）。该算法具有快速短脉冲（RaSP）序列，可以安全地跨血脑屏障输送药物。我们通过仿真（k波）和体外一周期，两周期和五周期脉冲的实验，将我们的分辨率与当前两种PAM算法的分辨率进行了比较。然后，我们测试了ATP-PAM体内并评估了重建的声源是否映射到大脑内的药物输送。在模拟和体外 对于所有测试的脉冲长度，ATP-PAM的分辨率都有所提高。 体内 小鼠实验表明，ATP-PAM可用于靶向和监测药物向大脑的递送。借助声波小波和飞行时间，ATP-PAM可以以大大提高的空间分辨率定位声源。