Broadband pulses in shear wave elastography

Abstract

Usually pulses used for shear wave elastography and ARFI are considered to be monochromatic; however, there are advantages to using broadband pulses and including the absorption characteristics of the tissues. A new broadband formulation for volume acoustic radiation forces is presented that accounts for the pulse shape and the changes it encounters propagating through tissues with frequency power law absorption properties. This equation reduces to the well know formulation for the continuous wave case derived by W. Nyborg. Ideal tone bursts employed in elastography have the same time average intensity tissue as continuous wave intensities, irrespective of length. Tone bursts in viscous media have turn-on and turn-off transients called “precursors” and “postcursors,” which can increase pulse amplitudes at the ends of the pulses [Szabo, JASA 45(1): 124–130 (1969)]. By accounting for absorption across a broader bandwidth pulse spectrum, these transient effects can be reduced. Their effects and the potential for pulse shaping are discussed.