[Reversible computed tomographic changes following brain tumor irradiation induced by the "early-delayed reaction" after radiation].

We analyzed the incidence, timing and appearance of reversible CT findings in 55 patients undergoing radiation therapy (dose 60 Gy) for brain tumors. Three patients had "early delayed reactions" within three months of irradiation. CT studies showed increased size of the central zone of necrosis with contrast enhancement in the form of rings or garlands. Differentiation between these findings and recurrence of tumor was possible only through follow-up studies.