Miniaturized 434 MHz Cavity Encapsulated Patch Antenna for Superficial Hyperthermia Treatment
Muthu Rattina Subash Ramu, Kavitha Arunachalam
Abstract
A 434 MHz patch antenna encapsulated in a planar metal cavity is reported for hyperthermia (HT) treatment of superficial cancers. The optimized patch antenna is 3.6 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \times$</tex-math></inline-formula> 3.6 cm with return loss > 20 dB, ―10 dB bandwidth of 14 MHz, and predominantly tangential electric field in the near field at 434 MHz. Antenna effective field size (EFS) and penetration depth observed from simulation are 17.22 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 1.26 cm, respectively. The antenna optimized using bulk body tissue was assessed on heterogeneous human body model followed by experimental verification on tissue-mimicking phantom and ex-vivo bovine tissues. Thermal EFS (TEFS) and thermal effective penetration depth (TEPD) of 20.92 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 2.05 cm measured in tissue phantoms are comparable to 18.61 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 2.19 cm determined in simulations. Experiments on homogeneous tissue phantom and heterogeneous ex-vivo bovine tissues show localized power deposition in agreement with the simulations. The metal encapsulated patch antenna with EFS to aperture area ratio of 1.33 is well suited for HT treatment of localized superficial cancer. It is also concluded that it could be used for designing planar array capable of delivering adjustable heating pattern to treat large area diffused superficial cancers.