3-D Microvascular Imaging Using High Frame Rate Ultrasound and ASAP Without Contrast Agents: Development and Initial In Vivo Evaluation on Nontumor and Tumor Models

Abstract

Three-dimensional imaging is valuable to noninvasively assess angiogenesis given the complex 3D architecture of vascular networks. The emergence of high frame rate (HFR) ultrasound, which can produce thousands of images per second, has inspired novel signal processing techniques and their applications in structural and functional imaging of blood vessels. Although highly sensitive vascular mapping has been demonstrated using ultrafast Doppler, the detectability of microvasculature from the background noise may be hindered by the low signal to noise ratio (SNR) particularly in deeper region and without the use of contrast agents. We have recently demonstrated a coherence based technique, acoustic sub-aperture imaging (ASAP), for supercontrast vascular imaging and illustrated the contrast improvement using HFR contrast-enhanced ultrasound. In this work, we provide a feasibility study for microvascular imaging using ASAP without contrast agents, and extend its capability from 2D to volumetric vascular mapping. Using an ultrasound research system and a pre-clinical probe, we demonstrated the improved visibility of microvascular mapping using ASAP in comparison to ultrafast Power Doppler (PD) on a mouse kidney, liver and tumour without contrast agent injection. The SNR of ASAP images improves in average by 10dB when compared to PD. Besides, directional velocity mappings were also demonstrated by combining ASAP with the phase information extracted from lag-1 autocorrelation. Threedimensional vascular and velocity mapping of the mouse kidney, liver and tumour were demonstrated by stacking the ASAP images acquired using 2D ultrasound imaging and a trigger-controlled linear translation stage. The 3D results depicted clear micro-vasculature morphologies and functional information in terms of flow direction and velocity in two nontumour models and a tumour model. In conclusion, we have

Investigating CXCR4 expression of tumor cells and the vascular compartment: A multimodal approach

“…High frequency, low intensity US was used to image both tumor models before and during perfusion with T140-MB and NT-MB through the tumor’s vasculature. Fig 3A shows representative US images after clutter-filtering for rejection of tissue signal with exceptional spatial resolution, allowing identification of microvessel [ 56 ].…”

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“…DMAS beamforming with CST technique depends on DMAS signals from two subsets of PW transmit angles. The idea of complementary subset is similar to that in [ 27 , 28 , 29 ] but is defined in the dimension of PW transmit angle instead of receiving channel. Specifically, DMAS beamforming is performed using the available PW transmit angles in each transmit subset and the beamforming output is denoted as and , respectively, for subset 1 and subset 2: where the weighting vector for subset 1 is related to the weighting vector for subset 2 by to ensure the complementary property.…”

Current Concepts in Multi-Modality Imaging of Solid Tumor Angiogenesis

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