Quantitative Frequency-Domain Passive Cavitation Imaging

Abstract

Passive cavitation detection has been an instrumental technique for measuring cavitation dynamics, elucidating concomitant bioeffects, and guiding ultrasound therapies. Recently, techniques have been developed to create images of cavitation activity to provide investigators with a more complete set of information. These techniques use arrays to record and subsequently beamform received cavitation emissions, rather than processing emissions received on a single-element transducer. In this paper, the methods for performing frequency-domain delay, sum, and integrate passive imaging are outlined. The method can be applied to any passively acquired acoustic scattering or emissions, including cavitation emissions. In order to compare data across different systems, techniques for normalizing Fourier transformed data and converting the data to the acoustic energy received by the array are described. A discussion of hardware requirements and alternative imaging approaches are additionally outlined. Examples are provided in MATLAB.

Delay multiply and sum beamforming method applied to enhance linear‐array passive acoustic mapping of ultrasound cavitation

“…All images are displayed over a 30 dB dynamic range, with 0 dB corresponding to the maximum pixel value in each image. As seen, the PSF size of 60‐mm source depth is larger than that of 40‐mm source depth, which is expected because the PAM resolution performance is limited by the diffraction pattern of the array . It can be seen in Fig.…”

“…When using a receiving array with large aperture and low f‐number, TEA algorithm can provide a good performance. However, it will result in poor resolution performance for the case where a narrow‐aperture array such as a standard B‐mode linear array is employed due to the limited diffraction pattern of the array . This study mainly focused on the performance improvement of linear‐array PAM.…”

“…This technique can offer satisfactory image quality in the narrowband case for stable cavitation, but the phase estimation is less efficient for the case of broadband or high‐frequency band . The frequency‐domain implementation of PAM can be achieved by beamforming the frequency band of interest, such as subharmonic and ultraharmonic (for stable cavitation) and broadband noise (for inertial cavitation), where the time delays are converted into the phase shifts for each of the frequency components . Compared with time‐domain PAM, frequency‐domain operation makes the frequency selection of different cavitation types simpler and easier, and can eliminate temporal quantization error due to the discrete temporal sampling .…”

MRI‐guided transurethral insonation of silica‐shell phase‐shift emulsions in the prostate with an advanced navigation platform

“…Previous studies have found that bubble activity from droplets or microbubbles can provide controlled heating and can be monitored with passive ultrasound imaging techniques . In order to reduce the inconsistencies in the experimental treatment arms observed in this study, the acoustic output should be modulated based on feedback of cavitation activity via passive cavitation imaging, plane wave B‐mode imaging, or color Doppler imaging …”

Dissolved oxygen scavenging by acoustic droplet vaporization using intravascular ultrasound

“…ADV was monitored using both B-mode imaging and passive cavitation imaging with an L7-4 linear array (Philips, Bothell, USA) connected to a Vantage 256 ultrasound research scanner (Verasonics, Kirkland, USA). Passive cavitation images were formed using a delay, sum, and integrate algorithm [9]. Summation was performed over the frequency band of 2–6 MHz to identify the location of IVUS emissions.…”