title: The depth-dependence of the biological effectiveness of 60Co gamma rays in a large absorber determined by dicentric chromosomes in human lymphocytes.
abstract: Radiobiological evidence is shown concerning a significant depth-dependence of the maximum relative biological effectiveness at limiting low doses (RBE(M)) of (60)Co gamma rays in a cubic polymethylmethacrylate (PMMA) phantom of 30 cm edge length. Using the dose-response curve for the dicentric data in human lymphocytes obtained in the present experiment at a depth of 20 cm, together with the comprehensive and consistent data set determined earlier at smaller depths of the PMMA phantom, there is an increase in the RBE(M) value by a factor of 2.18 +/- 1.25 at a depth of 20 cm relative to 1 cm in the phantom. All the dicentric data are based on identical exposure durations and irradiation temperatures as well as identical culture and evaluation conditions, with blood from the same donor.
authors.affiliation: Radiobiological Institute, University of Munich, 80336 Munich, Germany. Ernst.Schmid@lrz.uni-muenchen.de
authors.forename: Ernst
authors.initials: E
authors.lastname: Schmid
authors.forename: Hartmut
authors.initials: H
authors.lastname: Roos
authors.forename: Hans-Michael
authors.initials: HM
authors.lastname: Kramer
mesh_terms: D002478:Cells, Cultured; D002869:Chromosome Aberrations; D003037:Cobalt Radioisotopes / Q000009:adverse effects*; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D006801:Humans; D008214:Lymphocytes / Q000528:radiation effects*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods
chemical_list: D003037:Cobalt Radioisotopes