Elastic moduli of breast and prostate tissues under compression

To evaluate the dynamic range of tissue imaged by elastography, the mechani cal behavior of breast and prostate tissue samples subject to compression l oading has been investigated. A model for the loading was validated and use d to guide the experimental design for data collection. The model allowed t he use of small samples that could be considered homogeneous; this assumpti on was confirmed by histological analysis. The samples were tested at three strain rates to evaluate the viscoelastic nature of the material and deter mine the validity of modeling the tissue as an elastic material for the str ain rates of interest. For loading frequencies above 1 Hz, the storage modu lus accounted for over 93 percent of the complex modulus. The data show tha t breast fat tissue has a constant modulus over the strain range tested whi le the other tissues have a modulus that is dependent on the strain level. The fibrous tissue samples from the breast were found to be 1 to 2 orders o f magnitude stiffer than fat tissue. Normal glandular breast tissue was fou nd to have an elastic modulus similar to that of fat at low strain levels, but the modulus of the glandular tissue increased by an order of magnitude above fat at high strain levels. Carcinomas from the breast were stiffer th an the other tissues at the higher strain level; intraductal in situ carcin omas were like fat at the low strain level and much stiffer than glandular tissue at the high strain level. Infiltrating ductal carcinomas were much s tiffer than any of the other breast tissues. Normal prostate tissue has a m odulus that is lower than the modulus of the prostate cancers tested. Tissu e from prostate with benign prostatic hyperplasia (BPH) had modulus values significantly lower than normal tissue. There was a constant but not signif icant difference in the modulus of tissues taken from the anterior and post erior portions of the gland.