Interstitial microwave hyperthermia applicators having submillimetre diameters

Abstract

Using microscopic techniques we have fabricated interstitial hyperthermia applicators having diameters of 0·20, 0·33 and 0·58 mm, which will fit through catheters of 30, 26 and 22 gauge, respectively. Existing commercial applicators having a diameter of 1 × 1 mm required 17 gauge (or larger) catheters. Our new applicators, which operate at 915 MHz, are a smaller version of a design used by others. We have characterized our applicators by determining the energy deposition patterns (SAR) in muscle-simulating phantoms. These patterns were determined by measuring the electric field intensity using a miniature implantable isotropic probe having a diameter of 3 mm. Contours of the SAR data for our applicators, as well as a larger commercial applicator, show that all of these applicators exhibit similar heating patterns. Test results suggest that the durability and power handling capability of our submillimetre applicators are adequate for use in patients. Our new applicators should be useful in the percutaneous treatment of deep-seated tumours, intraoperative treatments, and also permit intraluminal or intravascular access to tumours.

Key Words:

• Applicator
• electromagnetic
• interstitial