[Hyperthermia of malignant brain tumors--development of an interstitial microwave hyperthermia system and study of thermodosimetry and heat toxicity in a canine brain model].
Hyperthermia is a promising important adjunct to conventional treatment of malignant brain tumors and available data suggest a strong biological rationale for its use. Hyperthermia has been shown to sensitize tumors to radiation, particularly radiation delivered at low dose rates typical of brachytherapy. To complement our clinical study of interstitial brachytherapy of malignant brain tumors, a microwave interstitial heating system with data acquisition has been constructed at UCSF. This system was evaluated in a phantom and in a series of non-survival and survival experiments for heating patterns and heat toxicity in 24 adult canine brains. A single 2450 MHz microwave heating antenna and 3 fiberoptic thermometry probes were placed stereotaxically into the frontal white matter of 24 dogs. Temperature measurements were made at 1 mm increments along the antenna length 5 mm from the antenna axis and radially away from the antenna junction. For the survival studies, minimum temperatures 43 degrees C, 44 degrees C, and 45 degrees C were maintained at points 5 mm from the antenna junction for 30 minutes. Hyperthermia-induced tissue damage was measured weekly following the heat treatment using CT. In general, it was easy to maintain a steady temperature state for a long time period. Heating patterns tended to be ellipsoidal, corresponding relatively well with those predicted by the phantom trials. Heat toxicity was examined by sequential quantitative CT scans in chronic trials and correlated with histopathology following sacrifice at 1-16 weeks. Neurological deficits were minimal and were restricted to the first day after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging / Q000502:physiology; D001932:Brain Neoplasms / Q000628:therapy*; D004285:Dogs; D006979:Hyperthermia, Induced / Q000009:adverse effects / Q000295:instrumentation*; D008872:Microwaves / Q000627:therapeutic use; D014057:Tomography, X-Ray Computed