X-Ray mammography currently misses an estimated 15 percent of breast cancer. It also has trouble imaging women with dense breasts and discriminating between benign and malignant masses. As an alternative, a characterization of benign and malignant breast tissues based on their reconstructed shape and permittivity profile has been presented by G. Bindu and K.T. Mathew from the Microwave Tomography and Materials Research Laboratory at Cochin University of Science and Technology.

Normal and benign breast tissues were collected from two patients. Normal and malignant breast tissues were then collected from two other patients. From each specimen, a thin, circular sample with a 6-mm diameter and 2-mm thickness was excised. To study each sample's water content, 10 g of every sample was subjected to a preheated oven at +70°C for 10 s. For microwave tomographic imaging, abnormal tissue of radius ~0.5 cm was inserted in the same person's normal tissue sample (which had a radius of ~1 cm).

The rectangular cavity perturbation model is used for an estimation of the tissues' dielectric properties. The cavity is made from S-band waveguide with both ends closed. The resonator's length determines the number of resonant frequencies. Bow-tie antennas with resonant frequencies of 2.985 GHz are used for transmission and reception. For data acquisition, the sample is illuminated by the bow-tie antenna at a frequency of 3 GHz. Two-dimensional (2D) tomographic images are reconstructed from the scattered fields using a distorted Born iterative algorithm. The imaging studies show that such tumors can be characterized at the industrial-scientific-medical (ISM) band. See "Characterization of Benign and Malignant Breast Tissues Using 2-D Microwave Tomo-graphic Imaging," Microwave and Optical Technology Letters, Oct. 2007, p. 2341.