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Relative biological effectiveness of 241Am relative to 192Ir for continuous low-dose-rate irradiation of BA1112 rat sarcomas.

Authors
  • Morton, J
  • Yabuki, H
  • Porter, E A
  • Rockwell, S
  • Nath, R
Type
Published Article
Journal
Radiation research
Publication Date
Sep 01, 1989
Volume
119
Issue
3
Pages
478–488
Identifiers
PMID: 2772139
Source
Medline
License
Unknown

Abstract

Sealed sources of 241Am have been developed for intracavitary irradiation of gynecological cancers. Relative to conventional isotopes (that is, 226Ra, 137Cs, 192Ir), 241Am allows for better shielding of dose-limiting normal tissues in the patient. In addition, the long half-life of 241Am (432 years) makes it an attractive isotope both for clinical use and for long-term radiobiology studies. Using a previously developed in vivo applicator system, BA1112 sarcomas on WAG/Rij Y rats were irradiated using 241Am or 192Ir at three different dose rates. Following in vivo treatment of the sarcomas with graded doses of radiation, cell survival curves were determined using an in vitro colony formation assay. The slopes of the resulting cell survival curves were observed to increase significantly as the dose rate increased from 0.30 to 0.60 Gy/h, then to decrease slightly as the dose rate increased from 0.60 to 0.95 Gy/h. The relative biological effectiveness (RBE) of 241Am relative to 192Ir was observed to increase linearly with increasing dose rate; the RBEs were 0.96 +/- 0.009, 1.09 +/- 0.12, and 1.17 +/- 0.11 at dose rates of 0.30, 0.60, and 0.95 Gy/h, respectively.

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