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PubMed1986

A new pulsatile flow visualization method using a photochromic dye with application to Doppler ultrasound.

A nonintrusive method for the visualization of pulsatile flow velocity profiles is described. The method is based on the use of a photochromic dye that is added to the fluid being studied and a nitrogen laser which excites the dye producing a marker "line" whose movement can be photographed. A microcomputer is used as a system controller, to coordinate the system timing and to manage the data transfer. The method used for analysis of the photographs to determine the velocity profiles is described. Examples are presented of instantaneous velocity profiles obtained from velocity waveforms that are similar to those of the femoral artery. In addition, application of the system for studying the relationship between Doppler ultrasound spectral recordings and flow velocity profiles is discussed.

Biomedical Engineering↗

PubMedDate not supplied

In vitro comparison of alternative methods for quantifying the severity of Doppler spectral broadening for the diagnosis of carotid arterial occlusive disease.

Quantitative analysis of continuous wave Doppler recordings is of clinical value in the noninvasive diagnosis of carotid arterial disease. Peak frequency measurements are useful and accurately detect severe stenoses but do not reliably diagnose minor or moderate stenoses because the measurement is dependent upon the probe to vessel angle, which cannot be measured accurately. Recent investigations have focused on efforts to overcome this limitation by quantifying the degree of spectral broadening that occurs as the result of flow disturbances downstream from a stenosis. In this study, an in vitro model was used to determine the optimum method for quantifying the instantaneous Doppler spectrum. The model generates blood flow velocity waveforms that are virtually identical to those found in the human internal carotid artery. Doppler recordings were made from normal tubes and distal to stenoses (39-87% cross-sectional area reduction). The spectra were quantified by the following angle-independent measurements: spectral broadening index and three standard statistical shape descriptors, namely the coefficients of variation, skewedness and kurtosis. Using this model, the results demonstrate an excellent relationship between the severity of the stenosis and each of spectral broadening index (r = 0.99), coefficient of variation (r = 0.96), and coefficient of skewedness (r = 0.99). The calculation of each of the measurements can be implemented quite easily, and a prospective trial is warranted to evaluate their clinical diagnostic accuracy.

Arterial Occlusive Diseases↗