Ovine Model to Evaluate Ovarian Vascularization by Using Contrast-Enhanced Sonography

This project was designed to evaluate an ovine model for the use of contrast agent to visualize the microcirculation of normal ovaries. Intraovarian vascularization was investigated in eight ewes by using contrast-enhanced power Doppler after intravenous injection of Sonovue at five different times during each of ten normal estrous cycles. Sheep under general anesthesia underwent transvaginal B mode and power Doppler ultrasound examination of both ovaries, then received two successive doses of 5 ml of Sonovue, one dose for each ovary. Each ovary was monitored after the contrast injection, and a 3-min video clip was stored for each side. The video clip was used to derive time–intensity curves, which were then used to derive the contrast parameters. A total of 108 doses of contrast agent were used; 93% of the injections were available for contrast enhancement analysis. The optimal dose was determined on the first two sheep. Enhancement was strongest and longest with the 5-ml dose. In one sheep, enhancement of both ovaries remained weak irrespective of the period of the cycle. No adverse side effects of Sonovue were seen in the sheep. Contrast injection improved visualization of ovarian microcirculation by 248% (95% confidence interval [CI], 210 to 285%) for 74.2 sec (95% CI, 68.2 to 80.2 sec). Ovaries on the side of ovulation had a stronger enhancement compared with the ovary with no ovulation (368% versus 175%, P < 0.001), but the enhancement time was the same. We concluded that the sheep is an excellent animal model to illustrate microcirculation enhancement by using Sonovue to demonstrate ovarian vascular changes.