Late brain necrosis in correlation with CT picture, dose distribution and radiobiological considerations

ABSTRACT

Out of 850 cases previously exposed to cranial irradiation, between January 1984 and January 1988, 300 cases were further reviewed and 15 patients were detected with clinical and CT findings suggestive of brain radiation necrosis that coincided with areas of high dose within the brain substance. The mean planned dose was 5667 cGy and the mean number of fractions was 28. The threshold dose at areas of necrosis ranged between 5100 cGy/23 fractions and 7000 cGy/30 fractions or 1043 and 1280 neuret. The biologically equivalent dose for brain necrosis ranged between 89 and 124 Gy. The lower doses were associated with larger brain volumes included. The total dose, dose per fraction and volume of tissue included were found of importance in determining the risk of brain necrosis. The median time between radiotherapy and necrosis was 31 months [21-47 months]