Automated quantitative analysis of the shift of frequency spectra generated by attenuated signals from contrast microbubbles.

The ultrasound-induced harmonic microbubble response spectrum is known to shift to lower frequencies with increasing tissue attenuation. We hypothesized that this shift could be reproducibly detected in received broadband radiofrequency spectra. We used an automatic Gaussian curve-fitting technique to measure the mean harmonic response generated by three different contrast agents at six incremental levels of attenuation.

Dual-spectra ultrasonography: an attenuation-compensating technique for myocardial perfusion analysis.

Objective: To validate the harmonic-fundamental frequency ratio peak for user-independent differentiation of myocardial perfusion under clinically relevant levels of signal attenuation.

Methods: Radio frequency data were obtained by using apical long-axis scans in 11 open-chest pigs during continuous infusion of a contrast agent after left anterior descending artery occlusion. Silicone pads were interposed between the transducer and the heart to simulate levels of thoracic wall attenuation.