|
The use of conformal antenna array in the treatment of superficial diseases can significantly increase patient comfort
while enhancing the local control of large treatment area with irregular shapes. Originally a regular square multi-fed slot
antenna (Dual Concentric Conductor - DCC) was proposed as basic unit cell of the array. The square DCC works well
when the outline of the treatment area is rectangular such as in the main chest or back area but is not suitable to outline
diseases spreading along the armpit and neck area. In addition as the area of the patch increases, the overall power
density decreases affecting the efficiency and thus the ability to deliver the necessary thermal dose with medium power
amplifier (<50W). A large number of small efficient antennas is preferable as the disease is more accurately contoured
and the lower power requirement for the amplifiers correlates with system reliability, durability, linearity and overall
reduced cost. For such reason we developed a set of design rules for multi-fed slot antennas with irregular contours and
we implemented a design that reduce the area while increasing the perimeter of the slot, thus increasing the antenna
efficiency and the power density. The simulation performed with several commercial packages (Ansoft HFSS, Imst
Empire, SemcadX and CST Microwave Studio) show that the size reducing method can be applied to several shapes and
for different frequencies. The SAR measurements of several DCCs are performed using an in-house high resolution
scanning system with tumor equivalent liquid phantom both at 915 MHz for superficial hyperthermia systems in US) and
433 MHz (Europe). The experimental results are compared with the expected theoretical predictions and both simulated
and measured patterns of single antennas of various size and shapes are then summed in various combinations using
Matlab to show possible treatment irregular contours of complex diseases. The local control is expected to significantly
improve while maintaining the patient comfort.
|
