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C W McCabe

Publications and source records attributed to C W McCabe.

5 recordsLinked to original sources
PubMedDate not supplied

Completely implantable hyperthermia applicator with externalized temperature monitoring: tests in conductive gel.

Development is underway on a hyperthermia applicator intended for complete implantation and long-term use. Radio frequency energy is transmitted from an external antenna to a closely coupled subdermal antenna. This internal antenna is connected via a transmission line to deeply implanted electrodes. Changes in temperature at the electrodes result in a change in tissue resistivity which modifies the complex impedance seen at the external antenna terminals. This variation in antenna impedance (magnitude and/or phase angle) can, in principle, be utilized to indirectly monitor and regulate tissue temperature at the electrode location. Test results from conductive-gel tissue phantom experiments are presented.

Animals↗
PubMedDate not supplied

Total implants for hyperthermia application and thermometry.

Tests have been performed in saline phantoms on a 6.78 MHz hyperthermia applicator designed for complete implantation; no conductors would penetrate the skin following the implant procedure. Energy is coupled across the skin from an external to an internal loop antenna: the latter is connected by transmission line to conventional r.f. tissue electrodes which are typically either parallel plates or arrays of cylindrical pins. In phantoms the technique produces deep, localized heating at a selected site without significant hearing at the 'subdermal' receiving antenna near the surface. In addition, the hyperthermia applicator may have potential as an indicator of temperature for the tissue volume at the deep site, since complex impedance at the external antenna is a function of tissue resistivity/temperature at the electrodes. Specifically, temperature at the deep site can be controlled effectively by regulation of the phase angle between voltage and current at the external antenna. A separate passive implantable electromagnetic-reflectance thermometer, energized by external electromagnetic fields, has been designed. This device, also tested in gel and water phantoms, is energized and interrogated by external r.f. fields and tracks a thermocouple to within +/- 0.1 degree C over the range of interest in clinical hyperthermia. The intended application for these devices is repeated, long-term hyperthermic treatment and thermometry of deep-seated malignant tumours following a single invasive procedure.

Electromagnetic Fields↗
PubMedDate not supplied

A technique for localized heating in tissue: an adjunct to tumor therapy.

Increasing evidence of the beneficial effects of hyperthermia in the treatment of tumors, particularly when combined with radiation therapy or chemotherapy, has created the need for practical methods of localizing heat in arbitrary tissue volumes. Heating superficial transplanted animal tumors in hot-water baths has been of considerable importance in research, but the method has very limited clinical application. Microwave diathermy and ultrasound diathermy are capable of greater penetration than external conduction heating, but are also generally limited to the heating of superficial tissue volumes. A more direct method for localized tissue heating is proposed: localized electric current fields produced with carefully specified electrode configurations. This technique, although often quite invasive, offers the possibility of heat localization in almost any treatment volume specified by the therapist. Variations in electrical and thermal properties of tissues can be exploited to improve the architecture of the treatment plan. Several electrode configurations are illustrated. Limitations of the technique are discussed.

Diathermy↗