Ultrasonic measurements of breast viscoelasticity

Mallika Sridhar, Michael F. Insana

Research output: Contribution to journalArticlepeer-review

Abstract

In vivo measurements of the viscoelastic properties of breast tissue are described. Ultrasonic echo frames were recorded from volunteers at 5 fps while applying a uniaxial compressive force (1-20 N) within a 1 s ramp time and holding the force constant for up to 200 s. A time series of strain images was formed from the echo data, spatially averaged viscous creep curves were computed, and viscoelastic strain parameters were estimated by fitting creep curves to a second-order Voigt model. The useful strain bandwidth from this quasi-static ramp stimulus was 10-2 ≤ω≤ 100 rads (0.0016-0.16 Hz). The stress-strain curves for normal glandular tissues are linear when the surface force applied is between 2 and 5 N. In this range, the creep response was characteristic of biphasic viscoelastic polymers, settling to a constant strain (arrheodictic) after 100 s. The average model-based retardance time constants for the viscoelastic response were 3.2±0.8 and 42.0±28 s. Also, the viscoelastic strain amplitude was approximately equal to that of the elastic strain. Above 5 N of applied force, however, the response of glandular tissue became increasingly nonlinear and rheodictic, i.e., tissue creep never reached a plateau. Contrasting in vivo breast measurements with those in gelatin hydrogels, preliminary ideas regarding the mechanisms for viscoelastic contrast are emerging.

Original languageEnglish (US)
Pages (from-to)4757-4767
Number of pages11
JournalMedical Physics
Volume34
Issue number12
DOIs
StatePublished - 2007

Keywords

  • Biomechanics
  • Breast cancer
  • Creep
  • Rheological models
  • Stroma

ASJC Scopus subject areas

  • Biophysics

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