Application of the Constant Exposure Time Technique to Transformation Experiments with Fission Neutrons; Failure to Demonstrate Dose-Rate Dependence
Abstract
A direct comparison of the effectiveness of fission neutron at high or several low dose-rates was carried out under identical conditions. Monolayers of exponentially growing C3H/10T1/2 cells were exposed at 37 deg C to reactor-produced neutrons. Survival or transformation induction were studied at five doses from 10(exp 5) to 94 cGy. In low dose-rate irradiations, these doses were protracted over 0.5, 1, 3 or 4.5 h, resulting in 17 different dose-rates. Up to six experiments were performed at each of five exposure times. Concurrently with transformation we studied cell proliferation in control versus cells irradiated at 40 cGY acute and a 4.5-h protraction and found no evidence of a shift in the cell cycle distribution among these cells. At a given dose and dose-rate, the effect of dose protraction on survival or transformation was assessed by the dose-rate modifying factor (DRMF, defined as the low:high dose-rate effect ratio at the same dose. Survival or transformation induction curves were nearly linear with initial slopes, respectively, of about 6.5 x 10(exp -3) or 6.2 x 10(exp -6) /cGY. Consistent with dose response curves, DRMFs were independent of the dose and dose-rate. The mean values of the dRMF with their uncertainties and 99 deg confidence intervals, based on measurements in individual doses and dose-rates for survival or transformation were, respectively: 1.01 + or - 0.03, 0.92, 1.09 or 0.98 + or - 0.04, 0.83, 1.08 indicating a similar precision in determining DRMF for survival or transformation, and no dose or dose-rate influence on these end points.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1994
- Accession Number
- ADA290028
Entities
People
- E. K. Balcer-kubiczek
- G. H. Harrison
- W. A. Mccready
Organizations
- Armed Forces Radiobiology Research Institute