Using UWB hyperthermia systems has the potential to improve the heat delivery to deep seated tumours. In this paper, we present a novel self-grounded Bow-Tie antenna design which is to serve as the basis element in a phased-array applicator. The UWB operation in the frequency range of 0.43-1 GHz is achieved by immersing the antenna in a water bolus. The radiation characteristics are improved by appropriate shaping the water bolus and by inclusion of dielectric layers on the top of the radiating arms of the antenna. In order to find the most appropriate design, we use a combination of performance indicators representing the most important attributes of the antenna. These are the UWB impedance matching, the transmission capability and the effective field size. The antenna was constructed and experimentally validated on muscle-like phantom. The measured reflection and transmission coefficients as well as radiation characteristics are in excellent agreement with the simulated results. MR image acquisitions with antenna located inside MR bore indicate a negligible distortion of the images by the antenna itself, which indicates MR compatibility.
Abstract-In hyperthermia treatment planning (HTP) the goal is to find the amplitudes and phases of antennas in the applicator to efficiently heat the tumor. To do this prior information regarding tumor characteristics such as the size, position and geometry, in addition to an exact model of the hyperthermia applicator is needed. Based on this information, the optimal frequency of operation can be determined. In this paper the optimum frequency for hyperthermia treatment based on the tumor and applicator characteristics, using time reversal as the focusing technique, is studied. As prior information, we consider tumor size and position, the number of the antennas in the applicator and the frequency characteristics. The obtained optimal frequency range is found using hyperthermia quality indicator values calculated from simulations. We also determine the optimum position of the virtual source in the initial step of the time reversal method to increase the quality of the treatment.
A comparative study of acceleration methods for computing the infinite series summation arising in parallelplate Green's functions is performed. The spectral summation, the application of the Shanks-transformed spatial summation, and the Ewald method are examined. Results are presented which show that, although the convergence rates of Ewald's method and the spectral summation are generally largest (i.e. less number of terms), the total series evaluation time for reaching a certain specified accuracy -which is ultimately of more practical importance -is shortest for the Shanks accelerated spatial summation for most of the cases we considered.
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