Some Measurements of Gamma-ray Doses Received by a Radiotherapist During Radium Operations

Origin of the linearity no threshold (LNT) dose-response concept

This paper identifies the origin of the linearity at low-dose concept [i.e., linear no threshold (LNT)] for ionizing radiation-induced mutation. After the discovery of X-ray-induced mutations, Olson and Lewis (Nature 121(3052):673-674, 1928) proposed that cosmic/terrestrial radiation-induced mutations provide the principal mechanism for the induction of heritable traits, providing the driving force for evolution. For this concept to be general, a LNT dose relationship was assumed, with genetic damage proportional to the energy absorbed. Subsequent studies suggested a linear dose response for ionizing radiation-induced mutations (Hanson and Heys in Am Nat 63(686):201-213, 1929; Oliver in Science 71:44-46, 1930), supporting the evolutionary hypothesis. Based on an evaluation of spontaneous and ionizing radiation-induced mutation with Drosophila, Muller argued that background radiation had a negligible impact on spontaneous mutation, discrediting the ionizing radiation-based evolutionary hypothesis. Nonetheless, an expanded set of mutation dose-response observations provided a basis for collaboration between theoretical physicists (Max Delbruck and Gunter Zimmer) and the radiation geneticist Nicolai Timoféeff-Ressovsky. They developed interrelated physical science-based genetics perspectives including a biophysical model of the gene, a radiation-induced gene mutation target theory and the single-hit hypothesis of radiation-induced mutation, which, when integrated, provided the theoretical mechanism and mathematical basis for the LNT model. The LNT concept became accepted by radiation geneticists and recommended by national/international advisory committees for risk assessment of ionizing radiation-induced mutational damage/cancer from the mid-1950s to the present. The LNT concept was later generalized to chemical carcinogen risk assessment and used by public health and regulatory agencies worldwide.

Personnel radiation exposure analysis in a radiotherapy center: fourteen year retrospective study

The radiation exposure to the staff in the Ontario Cancer Institute between 1964-1977 was analyzed based on data from personnel film monitors. The annual collective dose equivalent was found to vary from 320 to 720 person-mSv. Of this, about 75% was attributable to the use of radionuclides for intracavitary and interstitial therapy, about 17% the use of external radiation therapy equipment, and the remaining, about 8% was equally attributable to diagnostic X ray and a mixture of many radiation sources used in research. The most influential factor to the annual collective dose equivalent was the number of patients treated with intracavitary and interstitial therapy. The dose per such application to this population was about .70 mSv, and was further broken down into .48 mSv to nurses in the wards where these patients were admitted, .11 mSv to personnel who handle these sources, .08 mSv to the operating room staff, and .04 mSv to the others. The collective dose per external radiation daily treatment was about .0008 mSv. For a course of 20 treatments, the collective dose equivalent will be in the order of .02 mSv. For diagnostic radiology, the collective dose per patient visit was in the order of 0.0003 mSv.