Quantification of intravenous contrast-enhanced Doppler power spectrum in the rabbit carotid artery

In vivo evaluation of Doppler contrast agent (DCA) enhancement has been principally qualitative. To quantitate the enhancement of the Doppler signal by perflubron emulsion, an investigational DCA, the audio-Doppler signal from the rabbit carotid artery was recorded during 0.5-ml/kg incremental doses to a total dose of 2.5 ml/kg. A representation of the recorded signal intensity, the Doppler power spectrum (DPS), was determined using a personal computer and commercially available software package. The dose related enhancement from perflubron emulsion was linear (r = 0.986, p = 0.0124) with a 710% (8.5 dB) overall enhancement at 2.5 ml/kg (p = 0.0001). Significant differences in enhancement could be detected with doses as low as 1.0 ml/kg and compared favorably with observer assessment of dose-related enhancement. This relatively simple method of computer analysis can quantify in vivo Doppler signal intensity and enhancement by perflubron emulsion and may enable quantitative comparisons between different DCAs.