The Impact of Loss on Ultrasound Propagation
A marked feature of ultrasound propagation in most biological tissues is the frequency-dependent loss suffered by the pulse. The measurement of this parameter is generally accepted to be an important tissue parameter, but many artefacts, in particular those due to diffraction effects, compromise such an approach towards tissue characterisation. This paper considers a particular wave equation, that is valid for a linear Maxwell viscoelastic medium, which can be solved in three spatial dimensions, so that the full diffractive nature of a propagating pulse can be explored. For simplicity, axial symmetry is assumed, but such an idealisation is not a prerequisite. Some complexities associated with the measurement of loss are examined and the (exact) solution is used to underpin an artefact-free method for loss measurement. The Maxwell model solution is shown to have some implications for the measurement of speed of sound, even for linear propagation.
KeywordsMaxwell Model Signal Velocity Main Pulse Ultrasound Propagation Bubbly Liquid
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