A microwave imaging chamber using bowtie antennas for biomedical applications

Two microwave imaging chambers for breast cancer imaging are presented in this paper. The idea was to construct an imaging chamber that can be applied on one side of the breast of the patient. For this purpose, we reduced the size of the chamber (half of previous chamber) as present in [1], while making sure any size and volume of the breast can fit in it. The same bowtie antenna was used as in [1] because of several advantages such as easy to manufacture, fairly inexpensive, and extremely low profile. The antennas resonate at 2.6 GHz with return loss less than -15 dB in the chamber. The small size did not affect the performance of the antenna, such as s-parameters and radiation pattern, etc.. This imaging chamber consists of the six sides. Eighteen antennas were installed on the walls of the chamber (three antennas on each side of the chamber). High frequency structure simulator (HFSS) software is used in designing antenna and system models, as well as simulation with breast phantoms. A good agreement between simulated and measured S-parameters was observed. In order to check the performance of the modified imaging chamber, a water bottle is placed in the center of the chamber. The height of the target is 10cm, and the radius is 3cm. The back propagation method is used as the imaging algorithm. From reconstructing the image it can be seen that this imaging chamber has the capability of detecting smaller objects. In the second imaging chamber, a bowtie patch antenna with two sets of slots on the each side of the asymmetrical triangle patch, is used. The antenna resonates on dual frequencies of 2.4 GHz and 5.8 GHz. The return losses of the slotted bowtie antenna have almost the same matching level lower than -12 dB at 2.4 GHz and 5.8 GHz frequencies. The size of the antenna is 10 x 14.25mm (width x length). The flexible Taconic CER-10 (tm) material with a dielectric constant of 10 and a thickness of 1.52mm is used as the substrate of the antenna. The small size of the antenna can to a maximize number of antennas in the imaging chamber. The configuration of these two chambers will be discussed. And the performance of the slotted bowtie patch antenna will be presented, including its s-parameters, gain, radiation pattern and etc. The results show that this antenna is well suited in the bra shaped imaging chamber for medical application.