The quantitative analysis featured in this study seems to be useful in the diagnosis of intracranial hypotension. A small CSF leak below the limit of radioisotope cisternography resolution might be detected using this technique.

The thermal damage threshold of normal brain tissue was evaluated from immediate and delayed histological changes caused by hyperthermia treatment of normal monkey (Macaca fuscata) brains. A 2450 MHz microwave antenna and an antenna cooling system devised by our group were used for in terstitial hyperthermia treatment. The antenna within the cooling system was inserted through a small craniectomy under general anesthesia. The temperature at a reference point, 4 mm radially away from the surface of the cooling system, was maintained at 42, 43, 44, 45, or 46°C for 60 minutes. Eighteen animals were treated and sacrificed immediately after the treatment, while nine animals were treated and sacrificed 7 days after the treatment. The histological changes were studied microscopically on sec tions stained with HE or Kluver-Barrera's method. The non-survival experiment demonstrated that areas heated at 44°C or below showed no obvious irreversible changes. The survival experiment showed areas heated at 44°C or above developed coagulative necrosis. These histological findings in dicate that thermal damage occurs in normal brain tissue after heating at 44°C or above for 60 minutes, suggesting that the safety limit for brain hyperthermia is 43°C for 60 minutes.

No abstract