Displacement spectra under isometric muscle contraction: spectral Doppler study and theoretical models of ultrasound response and muscle contraction.

Objectives: The purposes of this work were to detect the microscopic displacements accompanying isometric muscle tissue contraction under different external loads, to explore their spectral characteristics, and to develop physical models capable of explaining the experimental data obtained.

Methods: By means of a spectral Doppler musculoskeletal ultrasound method, spectral characteristics of local isometric skeletal muscle tissue contraction were studied. In this method, the phased fluctuation (Doppler) algorithm is used to estimate tissue displacements within the given sample volume in real time, and the spectral characteristics of recorded displacements are determined.

Correlation functions and power spectra of Doppler response signals in ultrasonic medical applications.

Ultrasound Doppler methods are widely used in clinical practice as prospective investigational tool to study the vascular system and soft biological tissues. Meanwhile, the most general relationship between the power Doppler spectra, spectral characteristics of the scattering fluctuations and the probing ultrasound field parameters for some clinical implementations are still unexplored. Based upon the continuum model of scattering inhomogeneities, a set of the closed-form expressions for the correlation functions and the spectra of Doppler response of soft tissues and blood have been derived.