PubMed · 3560314
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F W Kremkau. 1987. Doppler shift frequency data.. https://doi.org/10.7863/jum.1987.6.3.167
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Deviation from plane wave conditions within the ultrasound beam of a Doppler blood flow detector leads to a non-linear relationship between the phase angle of the back-scattered signal and the scatterer position. This in turn leads to frequency modulation of the Doppler signal and an increase in the Doppler spectrum width. The relationship between the ultrasound beam and the observed signal spectrum has been investigated by employing a computer-based model of the ultrasound field which enabled the calculation of: 1, pressure (amplitude and phase angle) field distributions from plane disc and focused transducers with unapodized and apodized aperture field distributions; 2, the Doppler signal from a scatterer moving through the field; and 3, the spectrum of this signal. The increase in spectral width resulting from deviations from plane wave conditions was calculated by comparing this spectrum with that of the signal from which frequency modulation had been removed.
The diagnosis of lower limb deep vein thrombosis can be made rapidly by compression ultrasound. This noninvasive test has almost completely replaced contrast phlebography in some major hospitals in North America. Compression ultrasound is well suited for making the diagnosis of deep vein thrombosis, measuring its extent, and monitoring the draining veins of the calf for evidence of spread of calf vein thrombosis. The nature of the deep vein thrombus, whether it is obstructing or nonobstructing, can be determined with the additional use of color Doppler mapping, a technique that displays flowing blood as a color overlay to the 2-dimensional real-time ultrasound image. Serial noninvasive determinations of the extent of thrombus in the lower-extremity deep veins is now possible with this combined sonographic imaging approach. Monitoring of possible changes in the extent of the thrombus burden can now be undertaken in patients enrolled in trials assessing the efficacy of different thrombolytic regimens.
Color Doppler sonography is a noninvasive, rapidly performed, and relatively inexpensive imaging technique for use in the diagnosis of scrotal pathology. Its major and proven role is in the evaluation of patients with acute scrotal pain, for which it is likely to become the primary imaging modality. Further work is needed to determine whether color Doppler is a useful diagnostic adjunct in evaluating patients with varicoceles and scrotal masses.