This project was designed to detect the development of tumor neovascul
arity and determine if intravenous microbubble contrast improves visua
lization of otherwise undetectable tumors in an animal model. VX-2 car
cinoma was implanted into one thigh of 10 New Zealand white rabbits. T
umors were assessed without and with contrast at 1- to 4-day intervals
from day 3-19 postimplantation, using gray scale, color flow, pulse D
oppler and power Doppler imaging. Tumor vascularity was compared with
the contralateral thigh muscle, so each animal was its own control. Co
ntrast 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 inje
ction, color gain was decreased by 40% without compromising color inte
nsity. Neovascularity was detected by contrast injection before the tu
mor could be palpated or visualized by gray scale. Based on these data
, we conclude that enhancement of neovascularity by intravenous contra
st permits earlier detection and improved visualization of soft tissue
tumors in rabbits. (C) 1998 World Federation for Ultrasound in Medici
ne & Biology.