  In this paper, we would like to quantitatively measure the tumor volume
contained in the breast imaged by the Digital Breast Tomosynthesis (DBT), a
reconstructed 3D image. The estimated volume will add to the prognostic value
of risk classification of breast cancer. We develop an algorithm that offers an
alternative way of estimating the volume of the tumor in a breast. We segment
the region of interest by expressing the ratio of tumor region to normal region
as a function of the threshold value in the image. Next, we determine the
volume of the tumor region as a function of the threshold. We then find the
optimal threshold value that yields the volume of the tumor contained in the
breast with the rate of growth of the tumor volume function.
