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Title: Carbon Ion Irradiation of the Rat Spinal Cord: Dependence of the Relative Biological Effectiveness on Linear Energy Transfer

Purpose: To measure the relative biological effectiveness (RBE) of carbon ions in the rat spinal cord as a function of linear energy transfer (LET). Methods and Materials: As an extension of a previous study, the cervical spinal cord of rats was irradiated with single doses of carbon ions at 6 positions of a 6-cm spread-out Bragg peak (16-99 keV/μm). The TD{sub 50} values (dose at 50% complication probability) were determined according to dose-response curves for the development of paresis grade 2 within an observation time of 300 days. The RBEs were calculated using TD{sub 50} for photons of our previous study. Results: Minimum latency time was found to be dose-dependent, but not significantly LET-dependent. The TD{sub 50} values for the onset of paresis grade 2 within 300 days were 19.5 ± 0.4 Gy (16 keV/μm), 18.4 ± 0.4 Gy (21 keV/μm), 17.7 ± 0.3 Gy (36 keV/μm), 16.1 ± 1.2 Gy (45 keV/μm), 14.6 ± 0.5 Gy (66 keV/μm), and 14.8 ± 0.5 Gy (99 keV/μm). The corresponding RBEs increased from 1.26 ± 0.05 (16 keV/μm) up to 1.68 ± 0.08 at 66 keV/μm. Unexpectedly, the RBE at 99 keV/μm was comparable to that at 66 keV/μm. Conclusions: The data suggest a linear relation between RBE and LET at high doses for late effects in the spinal cord. Together with additional data from ongoing fractionated irradiation experiments, these data will provide an extended database tomore » systematically benchmark RBE models for further improvements of carbon ion treatment planning.« less
Authors:
 [1] ;  [2] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1] ;  [2] ;  [1] ;  [6]
  1. Department of Radiation Oncology, University Hospital of Heidelberg, Heidelberg (Germany)
  2. (Germany)
  3. Clinical Cooperation Unit Molecular Radiooncology, German Cancer Research Center, Heidelberg (Germany)
  4. Heidelberg Ion Beam Therapy Center (HIT), Heidelberg (Germany)
  5. Department of Biophysics, Helmholtz Center for Heavy Ion Research (GSI), Darmstadt (Germany)
  6. Department of Medical Physics in Radiation Oncology, German Cancer Research Center, Heidelberg (Germany)
Publication Date:
OSTI Identifier:
22420409
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Radiation Oncology, Biology and Physics; Journal Volume: 90; Journal Issue: 1; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; BRAGG CURVE; CARBON IONS; COMPARATIVE EVALUATIONS; FRACTIONATED IRRADIATION; LET; PLANNING; RADIATION DOSES; RATS; RBE; SPINAL CORD