Microwave for breast imaging?

When we hear the word microwave, we immediately think about the heating device we have in our kitchen. But the word microwave just means waves with wavelengths from ranging from 1 meter to 1 millimeter (corresponding frequencies are 300MHz to 300 GHz). Microwave technology has been used in several engineering fields, and biomedical engineering is no exception. Microwave technology is used in the Radio Frequency components for MRI, but it also can be used as an imaging modality of its own. Microwave Imaging is research in progress, but there have been a number of groups working on this, which makes me believe that this will be available soon.

What are the principles behind Microwave Imaging?
Living tissues have different electrical properties than those of air. Therefore, the setup usually involves a liquid around the object and where the antenna is also immersed, so that the interface is minimized. When microwave radiation interacts with living tissue, microwaves can be transmitted, reflected or dissipated (by heat). The penetration of the microwaves goes until about 10 cm. The transmitting antenna emits microwaves and other antennas receive the transmitted and reflected waves. (The transmitting antenna can also receive.) There are differences in the properties of healthy tissue and malignant tumors. The tumors cause the waves to suffer scatter and the waves have now different energy (frequency). With the information of the detected waves, an image can be obtained (through some complicated methods) or the signals can be analyzed.

Advantages of Microwave Imaging:
- Low Cost
- Non-ionizing radiation




The main clinical application of Microwave imaging is breast cancer. This is due to several reasons:
1. Breast tissues are usually above the 10 cm penetration limit.
2. Breast cancer screening will greatly benefit from a low cost and non-ionizing radiation, as well as less painful acquisition for the patients.
 



Image from here.

More about this technique can be read in:
Fear, E., Meaney, P., & Stuchly, M. (2003). Microwaves for breast cancer detection? IEEE Potentials, 22 (1), 12-18 DOI: 10.1109/MP.2003.1180933
Nikolova, N. (2011). Microwave Imaging for Breast Cancer IEEE Microwave Magazine, 12 (7), 78-94 DOI: 10.1109/MMM.2011.942702

Recent news about microwave imaging for breast cancer:
http://www.sciencedaily.com/releases/2013/04/130423211830.htm