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Session: Image Analysis - Cancer
Session starts: Friday 25 January, 13:00
Presentation starts: 13:00
Room: Lecture room 559

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Greet Baldewijns (Thomas More Kempen, MOBILAB, Kleinhoefstraat 4, B-2440 Geel, Belgium)
Maarten Strackx (KU Leuven, Dep. Elektrotechniek ESAT-MICAS, Kasteelpark Arenberg 10, B-3001 Leuven, Belgium)
Patrick Reynaert (KU Leuven, Dep. Elektrotechniek ESAT-MICAS, Kasteelpark Arenberg 10, B-3001 Leuven, Belgium)
Paul Leroux (KU Leuven, Dep. Elektrotechniek ESAT-MICAS, Kasteelpark Arenberg 10, B-3001 Leuven, Belgium)

Abstract:
UWB imaging used for breast cancer detection aims to be a low-cost, low-hazard alternative for the X-ray mammography which is currently the most frequently used method for breast cancer screening. It works in a similar way to that of ground penetrating radar. All elements of an antenna array successively direct a short UWB pulse into the breast. The reflected signals are then detected by one or more receiving antennas. This sweep results in a set of received signals. A 3D image of the breast can be constructed based on this received set of signals. Malignant breast tissue is visible on the resulting 3D image [1]. The antenna design is a critical part of this detection method. An antenna was developed based on [2]. In [2] the antenna is optimized to radiate into air. The presented antenna however has been optimized to work efficiently when in contact with a matching medium with dielectric properties similar to breast tissue. The antenna consists of 2 spiral elements of the same size printed on an FR4 substrate with a thickness of 1.6 mm. On the other side of the substrate a ground plane with two circular slots is printed. Both spirals and slots are symmetrically placed with respect to the microstrip line. To achieve the desired bandwidth, the number of turns, width and distance between the spiral structures were modeled using CST Microwave Studio©. In order to facilitate the placement of the antenna against the breast a FR4 substrate was added on top of the ground plane. A metallic backplane was added to reflect the otherwise lost backward radiation into the matching medium. The backplane was placed at 8 mm from the feeding substrate. At this distance the interference of the reflected waves with the non-reflected waves has a positive effect on the radiation pattern. The width of the top substrate and the ideal location of the metallic backplane were both determined using parameter sweeps. An SMA connector was used to feed the antenna. In order to characterize the antenna, the S11 bandwidth and radiation patterns were simulated and measured. The relative radiation pattern was found by measuring the transmission between two identical spiral antennas in the desired measurement plane. The S11 parameter was measured with the top of the antenna immersed in a matching medium. The simulated and measured S11 parameter shows a -10 dB bandwidth from 3.8 to 15 GHz. Both the near and far field confirm that the antenna radiates into the matching medium. The measurements confirmed the simulated characteristics of the antenna. Both simulations and measurements prove the usability of the antenna for UWB breast cancer detection.