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An Irradiation Technique for Laboratory Animals

M.R.C., Radiobiological Research Unit, Harwell, Berks

This excerpt was created in the absence of an abstract.

For some years it has been general practice in the fields of tolerance dosimetry and biological investigations, involving radiobiological effects on systems widely distributed throughout the body, to specify the administered dose as "the whole-body dose". This dose has usually been measured in air at the position of the incident surface of the body. Whilst this may be adequate in the case of the smallest animal—the mouse—and highly penetrating X or radiations, it has become clear from the work at this Unit (unpublished) that even in animals as small as rats, using a 250 kV X-ray machine, the attenuation of the incident beam is of great significance.

When a series of experiments on rabbits was projected, involving accurate comparisons of results in animals differing perhaps in weight by 40 per cent., it was clear that a more accurate technique of irradiation was required. Some improvement on a simple irradiation of the animal under a single beam was attempted in the transplant experiments of Dempster (1951), who used a bilateral system. Dose curves indicate that the total effect of summing two depth dose curves in opposite directions can be approximated to a uniform tissue dose in the animal. The uniformity quoted is about ± 8 per cent. for any one animal. However, the animals, irradiated laterally, are not of constant breadth, and parts such as the head will receive considerably higher doses.