Stereotactic treatment of brain lesions. Biopsy, interstitial radiotherapy (iridium-192 and iodine-125) and drainage procedures.

Integrating CT imaging techniques into stereotactic procedures makes it easy to puncture cysts, take biopsies from neoplastic and nonneoplastic lesions, and place radioactive material in tumors at exact and reproducible sites. A stereotactic program of interstitial radiotherapy in deep-seated brain tumors has been applied in 326 cases as of December 31, 1979 (270 cases using iridium-192 and 56 cases using iodine-125). The use of iodine-125 is now favored since it requires less radiation protection due to its soft 28-35 keV radiation; at the same time, however, it possesses a comparable half life of 60 days. In 126 cases, stereotactic biopsy was used exclusively for diagnostic purposes followed by open craniotomy or conventional radiation. Cystic brain tumors (i.e., craniopharyngiomas and cystic low grade gliomas) were permanently drained by insertion of Rickham reservoir catheters in 61 cases. Stereotactic ventriculocisternostomies were carried out in cases of hydrocephalus and drainage of suprasellar arachnoid cysts was performed in 15 cases. A simple method of projecting CT images onto stereotactic X-ray pictures provides an exact mapping of lesions within the actual stereotactic brain space. The results of this series of patients strongly suggest that exploratory craniotomies and free-hand punctures can no longer be advocated. No radiation treatment should be considered without histological confirmation. The more clearly the volume of a tumor can be defined, the more favorable the results of interstitial irradiation in otherwise unresectable tumors.