Non-invasive imaging with UWB

Cancer is the main killing disease and breast cancer is the most common tumor among women. Compared to other cancers, the survival rate in case of breast cancer is high when detected early. Therefore intense screening programs are initiated. The standard for detection of breast cancer is mammography, which has several disadvantages such as ionizing radiation, high false-positive and false-negative rates. Ultrasound or magnetic resonance imaging can be applied to find tumors too, but both are not suited for large-scale screenings. Researchers at Dartmouth college have shown that ultra-wideband (UWB) can be a solution as a complementary method. However, the principles on which their prototype relies are not explicitly mentioned. Their applied frequency range of 300 MHz to 3 GHz is not the one ruled by the Federal Communications Commission (FCC) or European Telecommunications Standards Institute (ETSI). The FCC ruled that UWB has to operate roughly in the band of 3.1 to 10.6 GHz, whereas the European regulation is somewhat more limited. The aim of this master thesis is to experimentally verify whether medical imaging is possible at the frequencies ruled by the FCC for UWB, whereas the power limitation was not taken into account. For imaging objects, such as human tissues, different means are needed. The permittiv-ity of a tissue depend on frequency and on the type of tissue. To measure the frequency dependence a means for illumination is needed. UWB is such a means that has several advantages. The large bandwidth of UWB provides good resolving of multipath and (partly) penetration of tissues is possible. Also lesions and noncalcified tumors can be detected by UWB because of their different nature. Regions that are dense and firm can be imaged, such as in the near of the chest wall or underarm. However, UWB has a trade-off between high resolution and maximum penetration depth. Because no equipment was available to use pulsed UWB signals, in this research a swept narrow-band approach is used to experimentally verify whether imaging at the frequencies of UWB is possible. Illuminating the tissue with UWB, scattered fields can be measured applying an array of antennas. These scattered fields can be mapped to an image, showing object shapes and their permittivities. Every tissue has a different amount of fluid content, by which their frequency behaviors differ. Using the parametrization given by Gabriel et al. [1]–[3], these theoretical iii curves can be compared to the measured ones. …