Reseach And Design On Conformal Antenna For Non-invasive Breast Cancer Microwave Hyperthermia

Nowadays, breast cancer has became one of the most deadly threat to women’s health. With the development of technology, more and more means of treatment appear. As one of the more effective methods, microwave heat therapy is developing rapidly. Microwave hyperthermia artificially increases tumour temperature to a peak value between 42℃ and 45℃ for a period of time without overheating the surrounding normal tissues. On one hand, it’s because dielectric parameters and conductivity in tumor tissue are much larger than that in normal tissue, on the other hand, blood flow volume in the tumor region is very small and heat dissipation is poor. These two reasons result in the accumulation of energy in the tumor region, which makes microwave technology used for breast cancer hyperthermia possible.Hyperthermia antenna, which is the most important part of the microwave hyperthermia system is also developing rapidly. In this paper, numerical simulation for treating breast cancer by near filed of conformal microstrip antenna is proposed along with theoretical interpretation and validation, the possibility of using this method is also explored.First of all, physical model of human breast and dielectric model at 2.45 GHz are designed, which provides a directly available simulation target. The organizations of the breast will be added gradually in the next work to make it look more like a real one.Then, planar, cylindrical and spherical microstrip antenna are introduced along with improved spherical microstrip antenna. After simulation and comparison, the best breast conformal spherical microstrip antenna has the best specific absorption rate(SAR) distribution, So spherical antenna is detailed studied. Only reflection coefficient S11 and SAR distribution in the model are concerned. Whether adding medium oil, changing the thickness of the substrate, changing the shape of the antenna patch(from circular patch to a toroidal one) as well as changing the size of ground and substrate are discussed to find the best SAR distribution in the model. Finally, when medium oil is absent, Substrate thickness is 2mm, cutted radius of small round ‘W’ is 15 mm, and size parameter of the ground and substrate ‘m’ is 150 mm, the best SAR distribution is obtained. Because microwave attenuates greatly in human tissue, microwave energy has already been totally attenuated or absorbed before arrving the cardiac and muscle layers, heartland don’t suffer a great microwave radiation. In order to improve speed, heart area after the breast can be removed in the later simulation.Moreover, by analyzing SAR distribution and Poynting vector distribution in the model and analogizing the gap radiation theory of planar microstrip antenna, the gap radiation theory of conformal circular microstrip antenna is explained. The pointing area of Poynting vector is the energy convergence point, so it’s pointing distribution helps us find the most concentrated area of the antenna radiation energy, which makes it easy to find the antenna energy convergence region.Finally, the breast model is refined and the simulation with skin added in the model is done. In order to obtain the best SAR distribution, the tumor should be put in the energy convergence area of antenna, which can be found by analysizing the pointing distribution of Poynting vector.This article is exploratory research, which must have some deficiencies, but it provides preliminary preparation, research foundation and theoretical explaination for the treatment of breast cancer using near-field conformal antenna.