MONITORING OF THE BORON NEUTRON-CAPTURE REACTION BY A SIMPLE ANIMAL-MODEL

Sodium borocaptate (BSH, Na2B12H11SH), a slow neutron-capture compound , was injected into the left forebrain ventricle of 1-week-old rats (1 50 mu g BSH/3 mu l phosphate buffered saline). After 90 min, the anima ls were irradiated by epithermal neutrons (LVR-19 nuclear reactor in R ez near Prague, flux density 8.8 x 10(7) neutrons 0m(-2)s(-1), 8 MW re actor power, 8.2 cGy/min) for 5, 10 or 20 min. The brains were examine d histologically 8 h after irradiation. In animals irradiated for 5 to 10 min (41 and 82 cGy-Eq, respectively) lethal damage of cells was fo und in the external granular layer of the cerebellum and the subependy mal layer of the forebrain. Irradiation for 20 min (164 cGy-Eq) caused more extensive destruction of cell populations in these regions and, in addition, dead cells appeared also in the more differentiated postm itotic compartments, namely the deeper layers of the cerebellum, layer s II/III of the cerebral cortex and corpus callosum. In the forebrain periventricular layer, the extent of cell damage was declining towards the olfactory bulbs. In intact animals, as well as in those injected only with the 150 mu l phosphate buffered saline, the radiation damage was low and limited only to the most sensitive dividing populations o f the cerebellum and the forebrain. The study demonstrates a different iation-dependent damage of the rat brain cells by alpha particles and presents a simple model for evaluation of the biological effectiveness of slow neutron beams constructed for neutron-capture therapy of tumo rs.