Abstract
Microplanar bream radiation, created by synchrotron radiation with a proper collimator, to tumor has been proposed by NSLS. However, its pathobiological effects on tumors and normal tissues are not fully understood. We have made a proper collimator made by tungsten and polymer film at 25 μm width and 200 μm intervals to produce 10 lines of slit beams at SPring-8. MR (0.04 to 13 kGy) is irradiated to a normal rat cerebellum in order to investigate the histopathological effects of its dose and time responses. The rat was anesthetized by intraperitoneal pentobarbital injection. There appeared no significant change in the cerebellum by the gross examination up to 2 kGy exposure at 3 to 20 days after irradiation. However, the area of apoptotic changes with multi stripe lines was already clearly observed especially in a granule cell layer of cerebellum at over 200 Gy by microscopic examination. The apoptosis became more clearly observed as dose increased after 3 hours or later. The number of apoptotic cells reduced gradually as time goes by, and the lesion appeared to be substituted by normal granule cells. At more than a dose of 2 kGy, the stripe-shaped apoptosis area became inarticulate and showed irradiation induced histologic vacuolar degeneration / colliquative necrosis in the whole irradiated lesion with increase of dosage. According to the observations, the significant and effective maximum allowable dosage which did not show any significant damages in the granule cell layer of the cerebellum in the intervals of the slit irradiation was estimated to be 1 to 2 kGy.
