Irradiation of Dog Brain with Single Doses of X-Rays

Abstract

It is not possible to selectively irradiate a single hemisphere of the dog brain with epithermal neutrons. Therefore, a whole brain irradiation study with photons was carried out to establish adequate controls for the normal tissue tolerance studies with boron neutron capture irradiation at the Finnish Research Reactor.1 The primary objective of the study was to obtain a radiation-induced dose effect curve for visible changes on computerised tomography after photon irradiation and to calculate the ED₅₀ to this change. Computerised tomography (CT), with contrast enhancement, was used to detect the changes in the brain, induced by radiation, after 20 months follow up. A secondary objective of the present study was to estimate possible differences in response between half brain and whole brain irradiation. The results of whole brain irradiation in dogs in the present study were compared to those obtained by Fike using half brain irradiation.2,3 For immobilisation of the dogs during high-energy photon irradiation an anaesthetic agent that does not suppress the arterial oxygen saturation (SpO₂) is needed. In this study we used general anaesthesia accomplished with intravenous (iv.) propofol as the induction agent and isoflu-rane as the maintenance agent to ensure the oxygen saturation of haemoglobin.