Stimulated acoustic emission: Pseudo-Doppler shifts seen during the destruction of nonmoving microbubbles

The purpose of this study was to evaluate the appearance and the characteri stics of stimulated acoustic emission (SAE) as an echo contrast-specific co lor Doppler phenomenon with impact on myocardial contrast echocardiography (MCE), Stationary microbubbles of the new contrast agent SH-U 563A (Scherin g AG) were embedded within a tissue-mimicking gel material, Harmonic power Doppler imaging (H-PDI), color Doppler and pulse-wave Doppler data were acq uired using an HDI-5000 equipped with a phased-array transducer (1.67/3.3 M Hz), In color Doppler mode, bubble destruction resulted in random noise lik e Doppler signals. PW-Doppler revealed short "pseudo-Doppler" shifts with a broadband frequency spectrum. Quantification of SAE events by H-PDI demons trated an exponential decay of signal intensities over successive frames, A strong linear relationship was found between bubble concentration and the square root of the linearized H-PDI signal for a range of concentrations of more than two orders of magnitude (R = 0.993, p < 0.0001), Intensity of th e H-PDI signals correlated well with emission power (R = 0.96, p = 0.0014), SAE results from disintegration of microbubbles and can be demonstrated by all Doppler imaging modalities, including H-PDI, Intensity of SAE signals is influenced by the applied acoustic power and correlates highly with the concentration of microbubbles, Because intensity of SAE signals correlates highly with echo contrast concentrations, analysis of SAE signals might be used for quantitative MCE. (C) 2000 World Federation for Ultrasound in Medi cine & Biology.