Optimization of a dual concentric conductor antenna for superficial hyperthermia applications

Abstract

Dual concentric conductor antennas (DCCs) have been proposed as effective radiators for microwave hyperthermia applications, due to simplicity of construction from flexible printed circuit board (PCB) material. With proper design, the power deposition (SAR) pattern is uniform across the DCC. The effect of a single antenna can be combined in conformal nonphased arrays to form a region of nearly flat temperature distribution over a large area down to 1-1.5 cm depth. In the past, DCC antenna performance was analyzed using in-house FDTD software. Recently available electromagnetic simulation software provides reduced simulation time, increased accuracy and a user friendly interface with the ability to sweep design parameters to achieve critical optimization goals. More detail on antenna loading conditions provides enhanced design accuracy by accounting for second order effects neglected in previous modeling. In particular, recent design efforts have focused on improving antenna efficiency and reducing losses and reflections in the feedline network. A second challenge involves measurement of antenna properties in conditions more similar to the treatment environment, since temperature and loading condition affect antenna radiation and thus design requirements. We present the challenges of both antenna design and characterization, along with preliminary results of recent design improvements.

Study of Water Bolus Effect on Sar Penetration Depth and Effective Field Size for Local Hyperthermia

“…Dielectric properties of fresh and distilled water are shown in Table 2. Shell of water bolus is often a thin PVC sheet [16] and can be neglected in calculations. Table 2.…”

Evaluation of a dual-arm Archimedean spiral array for microwave hyperthermia

“…The spiral structure forms a continuously variable diameter antenna that is inherently broadband, improving the device's insensitivity to variations in tissue loading conditions [26,[30][31][32]. Several groups have explored the use of spiral antennae for hyperthermia.…”

“…Several microstrip antenna designs, such as the MicrostripMicroslot applicator [11] and the Contact Flexible Microstrip Applicator (CFMA) [12][13][14][15] have exhibited favourable characteristics for use in hyperthermia treatments such as light-weight, an EFS approaching the outer dimensions of the radiating aperture and the ability to form antenna arrays for increased heating area. The largest microstrip array applicator to date is the Conformal Microwave Array (CMA) [2,3,[16][17][18][19][20] which utilizes an array of Dual Concentric Conductor (DCC) antennae [17,[21][22][23][24][25][26][27][28][29] formed from thin, multilayer flexible PCB material. The CMA applicator provides a light-weight and flexible design with the ability to conform to contoured anatomy and generate power deposition patterns tailored to irregular shaped areas of disease.…”

Multilayer conformal applicator for microwave heating and brachytherapy treatment of superficial tissue disease

“…ribs), air bubble perturbers between the coupling bolus and tissue surface, and variable thickness waterbolus [24]. More recently, design optimization of the DCC antennae has continued using commercial electromagnetic simulation software to further improve impedance match and radiation efficiency of the DCC apertures [33,34]. The complexity of CMA applicators has continued to increase, first by combining the heating capabilities of DCC slot apertures with non-invasive radiometric monitoring of tissue temperature [30,[35][36][37][38] and subsequently by adding the capability of simultaneous brachytherapy with heat treatments [10,20,39].…”