Ultrasonic mechanical relaxation imaging and the material science of breast cancer

A time series of strain images is acquired while applying a ramp-and-hold compression to measure viscous creep from which viscoelastic properties of breast stroma can be measured. The literature on the ultrastructure of breast connective tissue suggests that profound changes occur during tumor formation that may generate contrast for viscoelastic properties. We review the continuum mechanics of uniaxial compressions of hydrated polymers to develop the feature space for our imaging approach. Two examples of clinical breast images show classic sonographic and elastographic features, and also suggest that viscoelastic properties, particularly the first strain retardance time constant T₁, may provide unique diagnostic opportunities.