Detection of the breast tumors by ultra-wideband radar based microwave method

Cancer disease is among the first causes of death today. Cancer cells divide and multiply by uncontrolled and form tumor-named tissues. The resulting tumors squeeze and damage normal tissues. In addition, cancer cells can spread to different parts of the body, preventing them from functioning. Lung and prostate cancer in males and breast and uterine cancer in females are among the most common types of cancer. In order to be able to perform cancer treatment, it must be known at what stage the disease is. It is about the stage of the disease, the size of the tumor and how far it has spread. For example, breast cancer is considered to consist of 4 cases. As the disease progresses, that is, as the fourth stage is approached, the success rate of treatment decreases. However, it has been scientifically proven that the success rate in treatment can be close to 100% if the disease is detected in the first stage. Accordingly, it can be said that the problems caused by breast cancer can be solved to a great extent by early diagnosis. Therefore, the early detection of small-sized tumors has always been a topic for researchers. In recent years, the need for new medical imaging technologies for breast cancer detection has increased. The researches for the improvement of the systems have been accelerated. The main conditions to be considered in breast screening methods for imaging purposes are; The accurate and successful detection of malignant and small-sized tumors, producing high resolution images, low cost and providing a comfortable environment for illness. Various methods are available for imaging the breast. According to the techniques used in the methods, imaging applications vary, but obtaining an image that determines the existence, location and size of the tumor is common aim tumor of all of them. X-ray mammography, one of the most commonly used methods, allows the diagnosis of breast cancer using X-rays. However, the use of ionizing radiation in x-ray mammography and the necessity of compressing the breast are seen as negative aspects of this method. An alternative method of X-ray mammography is magnetic resonance imaging, in which ionizing radiation is not used. However, there are disadvantages in this method, such as the occurrence of low significance which may lead to adverse diagnosis, discomfort of the procedure, long duration and high cost of the method. Another method, ultrasonography, which is harmless, is unsuccessful in finding intramuscular tumors in dense fat breast tissue. It is less effective than the mammography method. For this reason, it is usually used as a support to the mammography process. In addition to the mentioned methods, which are mainly used, there are many methods such as digital tomosynthesis, magnetic resonance spectroscopy, thermography, optical imaging, electrical impedance tomography, diffuse optical tomography and microwave imaging. Each methods has positive and negative specialities. In this thesis study, imaging methods that can be done using microwave techniques have been investigated. One of these methods, 'ultrawideband radar based microwave imaging', has been described in detail. The method of monostatic measurement, which is one of the measurement types used in this method, has been investigated experimentally and successful results have been obtained. Sensors acting as receiver and transmitter in microwave based breast cancer detection systems, ie antennas, must have certain characteristics. For this reason, these antennas to be used should be specially designed. First of all, it is desirable that the working frequency range, in other words the bandwidth of the antenna, should be as high as possible. Because, sampling the scattered area more freely is the most reasonable way to increase the data collected in the imaging systems. The second important aspect of the antenna design is that the ratio of the power level of the back-to-front lobe of the antenna is low. The 3 dB width of the radiation beam, that is, the half power beam width, must be narrow. It can be said that an antenna having these characteristics will have a high signal-to-noise ratio, in other words a high gain. The directivity of an efficient antenna will be at the same high levels as gain. In addition to being highly directional, it is also desirable that they are stable, that the main lobes in the radiation should be focused on directions that are close to each other throughout the entire operating frequency range. Finally, the dimensions of the antennas to be used should be designed as small as possible. Thanks to this compact design, it is aimed that the antennas should be used easily in the systems and the sampling rate of the scattered area should be as high as possible. In summary, it is desirable that the antennas to be used in the detection of breast cancer by microwave imaging system should have a high gain and efficiency in a wide frequency band, high and stability, and a compact design. In this thesis study, two different planar monopole antenna designs with rectangular patches and circular patches with all the above mentioned features were made by using various modification techniques and optimization methods included in the simulation program. According to the simulation results which are seen as successful, the fabrication of the antennas have been realized. The parameters of the produced antennas were measured and tested. Simulation results and practical measurement results were observed to be compatible with each other. In this context, the first contribution of the thesis work was to add new antennas to the literature. One of the purposes of the measurements was to see how the designed antenna would perform when used in a ultrawideband radar-based microwave imaging system. The proposed antenna was aimed to show better performance compared to similar works. Also measurements were aimed making in time domain. The time-dependent changes of the signals reflected from the breast phantom were aimed to observe in tumorous and non-tumorous situations. Another purpose is to create an image using the obtained data. The mentioned aims have been accomplished, it was found that the designed circular patch antenna with planar monopole is suitable for ultrawideband radar based microwave imaging. The presence of the 6 mm sized tumor-mimicking object embedded in the breast phantoms was determined by examining the results in the frequency and time domain. Then, conclusions were made about the position and size of the object. Also, the obtained data was colored to form an image. The position and dimension values of the object were determined with high accuracy rates. Detection of a tumor at this size will ensure that the cancer is diagnosed at an early stage and that the rate of success in treatment is increased. This important achievement is thought to be the second contribution of the thesis work and will benefit from ongoing research.