Electric-field distribution near rectangular microstrip radiators for hyperthermia heating: theory versus experiment in water

Abstract

A rectangular microstrip antenna radiator is investigated for its near-zone radiation characteristics in water. Calculations of a cavity model theory are compared with the electric-field measurements of a miniature nonperturbing diode-dipole E-field probe whose 3 mm tip was positioned by an automatic three-axis scanning system. These comparisons have implications for the use of microstrip antennas in a multielement microwave hyperthermia applicator. Half-wavelength rectangular microstrip patches were designed to radiate in water at 915 MHz. Both low (epsilon r = 10) and high (epsilon r = 85) dielectric constant substrates were tested. Normal and tangential components of the near-zone radiated electric field were discriminated by appropriate orientation of the E-field probe. Low normal to transverse electric-field ratios at 3.0 cm depth indicate that the radiators may be useful for hyperthermia heating with an intervening water bolus. Electric-field pattern addition from a three-element linear array of these elements in water indicates that phase and amplitude adjustment can achieve some limited control over the distribution of radiated power.

A Patch Antenna Design for Application in a Phased-Array Head and Neck Hyperthermia Applicator

“…Since the 1970s, patch antennas have received a lot of attention [10] because they are inexpensive, lightweight, easy to construct and can be made to conform to curved structures. They have also been investigated extensively within the hyperthermia community [4], [11], [12], but mainly for purposes of superficial hyperthermia (SHT) (heating depth 4 cm). For SHT the most important drawback was its small bandwidth and the correspondingly large influence of tissue loadings in the close vicinity of the skin on the antenna's reflection characteristics.…”

Performance evaluation of a conformal thermal monitoring sheet sensor array for measurement of surface temperature distributions during superficial hyperthermia treatments

“…It should be noted that this paper does not address the ability of hyperthermia applicators to treat to any specific depth, but rather this thermometry approach will provide the critical information necessary to change power levels of multi-element applicators to deliver most uniform lateral distribution of heating across large superficial tissue disease [31]. Efforts thus far have been aimed at evaluating the prototype TMS for use in monitoring and control of surface temperature distributions under multi-element array microwave hyperthermia applicators like the 16-element Microtherm and 32-element CMA applicator developed for treatments of chest wall recurrence of breast cancer [1,5,32,33].…”

Compact Patch Antenna for Electromagnetic Interaction With Human Tissue at 434 MHz

“…Despite being optimized for unloaded far-field performance at 434 MHz, treatment clinics have successfully used loop [17], [32], dipole [18] and conventional square patch [33] applicator designs. The full-wavelength wire loop antenna dimensions are a loop inner radius of 113.5 mm, a loop outer radius of 115.5 mm and a feed gap of 1.8 mm.…”