Elastic Moduli of Breast and Prostate Tissues under Compression

Abstract

To evaluate the dynamic range of tissue imaged by elastography, the mechanical behavior of breast and prostate tissue samples subject to compression loading has been investigated. A model for the loading was validated and used to guide the experimental design for data collection. The model allowed the use of small samples that could be considered homogeneous; this assumption was confirmed by histological analysis. The samples were tested at three strain rates to evaluate the viscoelastic nature of the material and determine the validity of modeling the tissue as an elastic material for the strain rates of interest. For loading frequencies above 1 Hz, the storage modulus accounted for over 93 percent of the complex modulus. The data show that breast fat tissue has a constant modulus over the strain range tested while 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 of magnitude stiffer than fat tissue. Normal glandular breast tissue was found 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 than the other tissues at the higher strain level; intraductal in situ carcinomas were like fat at the low strain level and much stiffer than glandular tissue at the high strain level. Infiltrating ductal carcinomas were much stiffer than any of the other breast tissues. Normal prostate tissue has a modulus that is lower than the modulus of the prostate cancers tested. Tissue from prostate with benign prostatic hyperplasia (BPH) had modulus values significantly lower than normal tissue. There was a constant but not significant difference in the modulus of tissues taken from the anterior and posterior portions of the gland.

Anthropomorphic Phantoms for Assessment of Strain Imaging Methods Involving Saline-Infused Sonohysterography

“…The mean Young's storage modulus values for TM fibroid, TM myometrium/cervix, and TM fat given in Figure 7 and Figure 8 agree reasonably well with the values obtained by Kiss et al (2006), Krouskop et al (1998), andWellman (1999). The mean storage moduli of the TM fibroids, TM myometrium, and TM fat over the measurement time for the first phantom are 95, 30, and 7.4 kPa, respectively, and for the second phantom are 90 kPa, 44, and 8.1 kPa, respectively.…”

“…The mean value for the TM myometrium/cervix of the second uterine phantom is closer to the mean 40 kPa obtained by Kiss et al (2006) than that of the TM myometrium/cervix of the first uterine phantom. The mean TM fat storage moduli values for the first and second uterine phantoms are lower than the 18 ± 7 kPa obtained by Krouskop et al (1998), however they are closer to the human breast fat value of 5 kPa measured by Wellman (1999).…”

“…The values for the surrounding fat were chosen from Krouskop et al (1998) where the value of fat was from 18 ± 7 kPa. From Madsen et al (2006a), the mean Young's moduli of 10%, 30%, 50% and 70% (volume percents of safflower oil dispersed in gelatin) are 98, 65, 40, and 21 kPa, respectively.…”

“…Using the mean values of human breast fat provided by Krouskop et al (1998) and Wellman (1999) with the mean value provided by Kiss et al (2006) for the myometrium/cervix, the elastic contrast of fat is 0.45 and 0.125, respectively. The elastic contrast for the TM fat in the first and second uterine phantoms was 0.21 and 0.18, respectively.…”

A Hybrid Model of Tumor–Stromal Interactions in Breast Cancer

“…Furthermore, there will be little mechanical feedback on ECs and TECs from the surrounding tissue if the duct is not occluded, but after occlusion the surrounding tissue exerts a resistive force on the TECs that has been called the "reciprocal tissue resistance force" (Paszek and Weaver 2004). This force can have numerous effects, including an increase in the stiffness of the surrounding tissue (Krouskop et al 1998) and reorganization of the ECM (Paszek and Weaver 2004). Under normal conditions the biochemical and mechanical factors in the ECs and stroma are balanced and proliferation is controlled, but perturbations in this homeostatic state may initiate malignant transformation (Paszek and Weaver 2004).…”