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. 1. Introduction Blood vessel structure and patency are known to be related to the state and progression of many diseases [1, 2]. Abnormal vessel and vessel network morphologies have been positively correlated to malignancy across species [3, 4]. In preclinical studies of the disease and drug research, there are several noninvasive imaging modalities that can be utilized to visualize blood vessel structure. These are magnetic resonance imaging (MRI), computed tomography (CT), ultrasound, and more recently—photoacoustic imaging. To select one of these imaging methods, researchers must compromise between the variables of system including study cost, data acquisition time, ionizing radiation dose, imaging depth, and image resolution. High-field MRI is the most expensive, requires the longest acquisition times, and requires a dedicated facility for shielding and maintenance. CT is also fairly expensive, bulky, and primarily limited by a high ionizing radiation dose. Ultrasound is the least expensive, the most portable, and provides the fastest image acquisition. Photoacoustic imaging has similar portability to ultrasound and can provide high resolution images of the microvasculature as well as additional functional information (such as blood oxygen saturation), but is the most limited in penetration depth among these modalities. In the past, the reputation of ultrasound has been as a modality with limited
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