Martin Lindgren

Relation between Field Size and Tolerance of Rabbit's Brain to Roentgen Irradiation (200 kV) via a Slit-Shaped Field

The relation between field size and tolerance of rabbits brain to roentgen irradiation via slit-shaped field, 12 mm to 1 mm wide, was studied. Single skin doses between 2,100 r and 27,000 r were given. After 52 weeks the morphology of the lesions was analyzed. The frequency of injuries as well as the lowest focal dose which produced lesions were determined. The effect of irradiation decreased markedly with reduced width of slit. Resulting curves for the occurrence of necrosis and for discrete lesions are both S-shaped. The shape of the curves is discussed, especially the influence of diffusion processes. Published data on the area factor make it likely that the tolerance curve for the skin will be S-shaped too.