The theory of correlation functions and power spectra of doppler response signals in ultrasonic medical applications
Keywords:
Doppler ultrasound, Doppler spectrum, Doppler blood flow, power Doppler ultrasound, vibroelastography, spectral width, spectral broadening, pulsatile flow, tissue motionAbstract
Based upon the continuum model of scattering irregularities we have derived both a set of expressions for
the correlation functions and the spectra of Doppler response of soft tissues and blood flow-lines with an
allowance for different physical factors. The influence of the irregularity correlation radius magnitude and
the diffusion processes upon the spectra formed by stationary flows has been theoretically examined for
the Doppler technique for studying blood steams, which is widely used in cardiology. An increase in the
irregularity correlation radius and the accounting of their diffusion bring about an additional broadening
of the Doppler spectrum. The case of the non-stationary blood flow typical for the systolic cardiac phase
cycle has been examined and the condition for generating Doppler spectra are ascertained. We have
obtained analytical expressions for correlation functions and Doppler spectra for vibroelastography
technique to be used for diagnosing malignant tumors in soft tissues. In terms of the distinctive features of
the Doppler spectra thus obtained we have shown that it is possible to differentiate among the soft tissues
according to the magnitude of forced oscillations. The results obtained leads us to conclude that different
physical processes and characteristics of biological tissues affect the Doppler spectra and in this way are
indicative of improving the effectiveness of medical investigations.
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