Microwave and ultrasound imaging for biomedical tissue identification

Microwave tomography (MWT) and ultrasound tomography (UT) are two biomedical imaging modalities which are currently being investigated for applications such as breast cancer imaging. In MWT, the object of interest (OI) is surrounded by a number of antennas that are used to radiate the OI successively with electromagnetic waves in the microwave frequency range. The scattered electric fields are collected at receiver locations surrounding the OI. On the other hand, in UT the OI is surrounded by several ultrasound transducers illuminating the OI by acoustic waves and the scattered pressure from the OI is then collected at the receivers. In both MWT and UT, the scattered data is given to an inverse scattering algorithm to reconstruct specific properties of the object: in MWT the relative permittivity and conductivity (or complex permittivity) of the OI are reconstructed, whereas in UT the complex compressibility and inverse density are reconstructed. Both are quantitative imaging methods and thereby provide some insight into type of tissue corresponding to a pixel value in the image.