Most techniques for contrast-enhanced ultrasound imaging require linear propagation to detect nonlinear scattering of contrast agent microbubbles. Waveform distortion due to nonlinear propagation impairs their ability to distinguish microbubbles from tissue. As a result, tissue can be misclassified as microbubbles, and contrast agent concentration can be overestimated; therefore, these artifacts can significantly impair the quality of medical diagnoses. Contrary to biological tissue, lipid-coated gas microbubbles used as a contrast agent allow the interaction of two acoustic waves propagating in opposite directions (counter-propagation). Based on that principle, we describe a strategy to detect microbubbles that is free from nonlinear propagation artifacts. Invitro images were acquired with an ultrasound scanner in a phantom of tissue-mimicking material with a cavity containing a contrast agent. Unlike the default mode of the scanner using amplitude modulation to detect microbubbles, the pulse sequence exploiting counter-propagating wave interaction creates no pseudoenhancement behind the cavity in the contrast image.,
Physics in Medicine and Biology
Department of Cardio-Thoracic Surgery

Renaud, G., Bosch, H., Sijbrands, E., Shamdasani, V., Entrekin, R., de Jong, N., & van der Steen, T. (2012). Counter-propagating wave interaction for contrast-enhanced ultrasound imaging. Physics in Medicine and Biology, 57(21). doi:10.1088/0031-9155/57/21/L9