COMPARATIVE EFFECTS OF 50 KVP AND 250 KVP X RAYS ON THE DOG
Abstract
The subject of relative biological effectiveness of various ionizing radiations has been difficult and vexing to handle meaningfully when tissue distribution of dose is not uniform. It has been suggested by some that problems relating to linear energy transfer in tissues should appropriately be divided into two components - that relating to macroscopic energy distribution and that relating to energy distribution in terms of individual ionizing events. We have evaluated principally the former effect by looking at the biological potency of a lower energy X-ray source (50 kvp) in the dog. Previously we have shown that no single dose parameter is adequate to express the biological potency of lower energy X rays, although it was suggested that, to the extent that it was possible to measure it, the dose to the critical organ, usually bone marrow, would be the most significant. Further studies have been completed on dogs exposed to high doses of X radiation from a 50 kVp beryllium window generator. Doses of 4000 to 10,000 rad (air) at the potential midline of the subject have been shown to be as effective as doses of 200 to 300 rad of 250 kVp X rays. Hematological comparisons of the two radiations show close correlation with mortality and a relative potency factor of 1 for 30 the lower energy radiation. The lethal dose of 50 kVp X rays for the dog is 7500 r (air). Serious lesions of the skin were seen as a complicating factor at all doses in excess of 4000 r (air). Dosimetry was done in tissue equivalent ("Mix D") wax phantoms using the rotational exposure method which is routine in this Laboratory. Phantom depth dose measurements with miniature ion chambers and chemical dosimetry in agar gels yielded essentially identical values of 3% for midline tissue dose.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 24, 1963
- Accession Number
- AD0400635
Entities
People
- E. L. Alpen
- S. J. Baum
Organizations
- Naval Radiological Defense Laboratory