Quantitative estimation of spectral broadening for the diagnosis of carotid arterial disease: method and in vitro results.

For the quantitative assessment of carotid arterial disease using continuous wave Doppler ultrasound, the choice of an index to describe the degree of spectral broadening is important. It is shown that a spectral broadening index (SBI) given by 100(1 - fmean/fmax) and evaluated over a 25 msec period around peak systole is relatively insensitive to artifacts and has potential for achieving good clinical sensitivity. Furthermore, it can be implemented very simply on a microcomputer for on-line display. A description of a microcomputer based system, together with the results obtained using an in vitro flow model that closely approximates the carotid flow velocity waveform, are presented. Results relating the SBI to the degree of stenosis, recording site, and angle of insonation, are given. In addition, the results obtained with a commercial system that computes SBI based on the power spectrum, are presented for comparison.