Acoustic streaming in ovarian cysts

Objective. The purpose of this study was to investigate the hypothesis that endometriomas do not show acoustic streaming and then to quantify the streaming velocity of the particles within ovarian cysts that do show acoustic streaming. Methods. Ovarian cysts greater than 2 cm in diameter, with internal echoes seen on B-mode sonography, were prospectively evaluated for the presence of acoustic streaming. If acoustic streaming was present, a 2-mm pulsed Doppler sample volume was then placed within the distal portion of the cyst, and the streaming velocity was recorded. Follow-up included review of subsequent sonographic examinations, surgical notes, and histopathologic reports, with the latter being considered the final results if available. Results. Acoustic streaming was detected in 10 (38%) of 26 ovarian cysts, but of the 10 endometriomas, none (0%) showed acoustic streaming (P = .002). Acoustic streaming was detected in 86% (n = 6) of cystadenomas. Four of these were serous cystadenomas, which all showed acoustic streaming, with a velocity range of 1.5 to 3.6 cm/s. Two mucinous cystadenomas showed acoustic streaming with velocities of 0.8 and 2.0 cm/s. Conclusions. Endometriomas appear as cysts containing homogeneous, low-level, 'ground glass' echoes on gray scale sonography. Other types of ovarian cysts can also have these appearances. Endometriomas do not show acoustic streaming. Cystadenomas may have streaming velocities within a defined range. Acoustic streaming assessment may therefore prove to be an additional useful tool in assessing ovarian cysts and in completely excluding endometrioma as a diagnosis if a cyst shows acoustic streaming