Poster Presentation 26th Lorne Cancer Conference 2014

Implications of the scattered radiation of the synchrotron beam for investigation of long range bystander effects (#204)

Alesia Ivashkevich 1 , Carl N Sprung 1 , Helen Forrester 1 , Andrew W Stevenson 2 , Christopher J Hall 2 , Olga A Martin 3 , Pavel Lobachevsky 4
  1. Centre for Innate Immunity and Infectious Diseases, Monash Institute of Medical Research, Melbourne, VIC, Australia
  2. Australian Synchrotron, Melbourne, VIC, Australia
  3. Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne, VIC, Australia
  4. Molecular Radiation Biology Laboratory, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia

The out of field or bystander effects of radiation are well established in experimental settings and observed in cancer patients subjected to radiation therapy. Synchrotron radiation presents a convenient tool for investigation of bystander effects in cell and animal models given the well defined and controllable geometry of the synchrotron beam. Such an investigation is also important in the context of potential advantage of the synchrotron microbeam radiotherapy (MRT) as compared to the conventional radiotherapy. The contribution of dose exposure from the scattered radiation, however, is a concern in the studies of bystander effect. Therefore, the purpose of the present study was to evaluate the potential role of the scattered radiation in a forthcoming investigation of bystander effects induced by synchrotron radiation in biological in vitro and in vivo models. We employed radiochromic XRQA2 film based dosimetry to measure absorbed dose of the scattered radiation in several locations at various distances from a target exposed to MRT and conventional broad beam (BB) X-ray radiation produced by the Imaging and Medical Beamline at the Australian Synchrotron. In parallel, we investigated the yield of gamma-H2AX foci in cultured cells positioned at the same locations, and evaluated the absorbed dose from these yield values based on the dose response of gamma-H2AX foci count that was established in a separate experiment. Our results demonstrated the dependence of the level of scattered radiation on the distance, dose in the target zone and beam mode, and the correlation of absorbed dose values measured by physical (radiochromic film) and biological (gamma-H2AX assay) methods. The results indicated that the gamma-H2AX assay can be exploited as a biodosimeter for low doses in the range starting from a few mGy, and potentially able to detect the scattered radiation contribution to bystander effects induced by synchrotron radiation.