Acoustic Angiography: A New Imaging Modality for Assessing Microvasculature Architecture

Abstract

The purpose of this paper is to provide the biomedical imaging community with details of a new high resolution contrast imaging approach referred to as “acoustic angiography.” Through the use of dual-frequency ultrasound transducer technology, images acquired with this approach possess both high resolution and a high contrast-to-tissue ratio, which enables the visualization of microvascular architecture without significant contribution from background tissues. Additionally, volumetric vessel-tissue integration can be visualized by using b-mode overlays acquired with the same probe. We present a brief technical overview of how the images are acquired, followed by several examples of images of both healthy and diseased tissue volumes. 3D images from alternate modalities often used in preclinical imaging, contrast-enhanced micro-CT and photoacoustics, are also included to provide a perspective on how acoustic angiography has qualitatively similar capabilities to these other techniques. These preliminary images provide visually compelling evidence to suggest that acoustic angiography may serve as a powerful new tool in preclinical and future clinical imaging.

In-vivo quantitative analysis of the angiogenic microvasculature in tumor-bearing rats using multiple scattering

“…Previous work by our group suggests that characterization of angiogenesis can be an effective tool in distinguishing the tumor. (Gessner et al, 2013;Rao et al, 2016;Shelton et al, 2016) The smallest of these vessels have diameters on the order of a few microns (Tsuji et al, 2002). Conventional ultrasonic imaging methods do not allow for the resolution of single micro-vessels, although new "super-resolution" methods have recently been developed allowing…”

Development of transmitters in dual-frequency transducers for interventional contrast enhanced imaging and acoustic angiography

“…Using conventional ultrasound for imaging blood flow in micro vessels is challenging due to weak ultrasound scattering from blood [1]. Thus, superharmonic imaging, also referred to as acoustic angiography when using a high frequency receiver, was developed because of its capability of producing high resolution images of blood vessels [1,2].…”

“…Thus, superharmonic imaging, also referred to as acoustic angiography when using a high frequency receiver, was developed because of its capability of producing high resolution images of blood vessels [1,2]. In this technique, microbubbles are usually excited by low frequency acoustic waves (1-4 MHz) with moderate peak negative pressure and short pulse length near the resonant frequency of microbubbles; the high frequency (> 15 MHz) nonlinear echoes from microbubbles are received by a high frequency receiver [3,4].…”

“…Proper frequency combinations that produces high contrast-to-tissue ratio in super harmonic imaging, and high resolution have been reported [2,3,5,6]. However, the main challenge of this imaging method to date has been the lack of dual-frequency transducers that can transmit energy at a selected low frequency and simultaneous confocal detection of high frequency scattered echoes [1]. Dual-frequency transducers for interventional ultrasound imaging applications such as transrectal ultrasound and intravascular ultrasound (IVUS) need to be designed considering the spatial limitation.…”

“…However, the design concept and important design parameters for dualfrequency super-harmonic imaging transducers have not been extensively reported so far. The 4/30 MHz dual frequency transducer design was introduced with highfrequency 3-D contrast imaging of in vivo microvasculature [1,5], but the transducer size was not practical for interventional applications. Recently, the sandwich design of a small-aperture 6.5/30 MHz transducer made of PMN-PT crystals for the application of the contrast enhanced intravascular ultrasound (CE-IVUS) has been reported [7].…”