Contrast-enhanced sonography of tumor neovascularity in a rabbit model

This project was designed to detect the development of tumor neovascularity and determine if intravenous microbubble contrast improves visualization of otherwise undetectable tumors in an animal model. VX-2 carcinoma was implanted into one thigh of 10 New Zealand white rabbits. Tumors were assessed without and with contrast at 1- to 4-day intervals from day 3-19 postimplantation, using gray scale, color flow, pulse Doppler and power Doppler imaging. Tumor vascularity was compared with the contralateral thigh muscle, so each animal was its own control. Contrast injection improved visualization of tumor neovascularity. Early tumors had homogeneous vasculature but, with time, the centers became less vascular, while the periphery increased. Following contrast injection, color gain was decreased by 40% without compromising color intensity. Neovascularity was detected by contrast injection before the tumor could be palpated or visualized by gray scale. Based on these data, we conclude that enhancement of neovascularity by intravenous contrast permits earlier detection and improved visualization of soft tissue tumors in rabbits.