Detectability of small tumor vessels using color Doppler sonography in an experimental setting

Purpose. We present an experimental, statistical approach to estimate the s ize required for small vessels to become detectable with color Doppler sono graphy. Materials and methods. A murine experimental tumor was examined with color Doppler sonography after injection of 1.5 ml of the contrast medium Levovis t. Histologically, we measured vessel diameters inside the tumor as well as other, clearly identifiable locations. Results. With color Doppler at a transmit frequency of 7 MHz, vessels were only detected in the tumor's environment, but not inside. From the 95% quan tiles of the vessel diameter distribution found histologically, we estimate that vessels 80-140 mum in diameter or above may be detectable with color Doppler sonography, while vessels 40 mum in diameter or smaller are indetec table. Conclusions. Although a direct sonographic - histologic correlation is impo ssible for small vessels, a systematic assessment of the size distribution in clearly identifiable regions permits to estimate the sensitivity of colo r Doppler to detect blood flow in small vessels. According to our results, capillary blood flow is indetectable,and precapillary vessels may be detect ed only under optimal conditions.