The Relation of Radiation Dose to Radiation Damage in the Tibia of Weanling Rabbits injected with Strontium 90

Abstract

A comparison of radiation damage and radiation dose in the proximal half of the tibia of weanling rabbits following a single injection of ⁹⁰Sr at two dose levels, 100 and 600 μc/kg, has been made in animals killed at various time intervals up to six months later. An attempt has been made to quantitate the histological changes observed. Relatively little damage was seen at the lower dose level. At the higher dose level there was gross damage. The earliest damage was to the cells in the region of maximum proliferation immediately beneath the epiphyseal plate, within one day of injection. Disturbance of the blood vessels and epiphyseal cartilage plate was first observed at three days. Areas of abnormal cellular proliferation, presumed to be presarcomatous lesions, were seen in osteogenic connective tissue at three months, in regions which had received an accumulated dose of about 10,000 rads. Small discrete early tumours were sometimes noted in a region which had accumulated a similar dose. Multiple frank osteosarcomas had developed by six months. The lack of quantitative methods in histology is emphasised, and the difficulties involved in determining “the carcinogenic radiation dose” are discussed.