Iodine-125 interstitial irradiation of virally induced dog brain tumours.

Brain tumours were induced by intracerebral inoculation of beagle puppies with Avian sarcoma virus (ASV) suspension. The inoculation produced solitary or multiple sarcomas in three dogs and intraventricular anaplastic gliomas in four dogs. At the time of the first tumour positive CT-control Iodine-125 seeds (activity 8.5-10.5 mCi) were placed into the lesion. The radioactive Iodine-125 implants produced sharply delineated calcifying necroses with vital unaffected tumour outside the necrosis. The necrotizing and calcifying effect was apparent after 18 days and complete after 97 days when a transitional zone was no longer detectable. The response of neoplastic tissue to low dose rate interstitial irradiation was distinctly different in terms of the volume of necrosis when compared with Iodine-125 radionecroses in healthy brain tissue.