Hyperthermia

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Hyperthermia

Hyperthermia is an antitumoral therapeutic modality. It consists of selective heating of tumors to temperatures above 42 degrees Celsius, while maintaining healthy tissue nearer to physiological temperatures.

Hyperthermia is currently being used as an adjunct to radiation therapy and chemotherapy of superficial malignancies at a number of medical institutions around the world. Nevertheless, use of hyperthermia is limited, compared to chemo- and radiotherapy, despite reported efficacy in both laboratory and clinical application.

This phenomenon is due primarily due to lack of efficient heating applicators capable of heating large volume (or area) tumors that typically require adjuvant therapy up to therapeutic temperatures. In addition, the lack of reliable temperature feedback control systems which can be implemented noninvasively, limits the options of clinicians during treatment. Devices designed to heat these superficially localized (<2-3 cm depth), and often large area disease sites, must satisfy criteria associated with tissue heterogeneities, conformity to body contours, thermometry, patient safety, and production cost. Physiological and anatomical factors increase the complexity of achieving acceptable performance of microwave applicators.

Early microwave hyperthermic antenna designs, had a tendency to be bulky and awkward to couple to the human body. A variety of more or less adequate printed-circuit applicator designs have been proposed for hyperthermia to improve conformity to the body structures. This includes rectangular, circular, ring, spiral, and other more advanced patch radiator shapes.

During the 1990's a new generation of specialized applicators have been developed for superficial heating. The applicators present the following properties:

• Lightweight and at least partly flexible for fixation over a tumor.
  
• Effective power deposition pattern extending to the periphery of the aperture.
  
• Relatively simple and low-cost construction.