[Correlation between radiological, scintigraphic and histological changes in bone in rabbits following irradiation...

The left hind legs of eight rabbits were irradiated with 1.750 rad in a single dose or with 4,650 rad divided over a period of three weeks. These animals, as well as four who had not been irradiated, were examined periodically radiologically and with 99m Technetium pyrophosphate scintigrams during one year. No difference could be detected between the results of the single and fractionated doses. Scintigraphically there was a biphasic increase in uptake, the first peak co-inciding with the irradiation and of vascular origin, whereas the second peak occurred at four months and was due to a change in bone metabolism. At the end of a year uptake in the irradiated limb was slightly reduced. The earliest radiological changes were found after six months, at the end of the second scintigraphic peak; they consisted of coarsening and blurring of the trabeculae, nonhomogeneous spotty mineralisation and endosteal scalloping. Six animals developed a radiation-induced bone sarcoma, first demonstrated either by scintigraphy or radiology depending on its histology. The value of combining radiological and scintigraphic examinations for the early detection of post-radiation abnormalities is stressed.