Cytogenetic follow-up of an individual after accidental exposure to industrial radiation using dicentric frequency in blood lymphocytes.

A radiation accident occurred in Bursa, Turkey, in July 2005. An industrial radiographer was exposed to industrial iridium-192 gamma rays for 5 h while laying the natural gas line. After 5 h, the victim had a break because of vomiting and nausea. He ended his work, considering that he might have been exposed to radiation. In a few days, erythema, pain, desquamation, edema started in both hands of the victim. The biological dose assessment was started based on frequencies of dicentrics and rings in peripheral blood lymphocytes ten days after the radiation accident. 6 repeated blood samples were taken for 9 years and analyzed staining after giemsa. After 9 years, decline at dicentric frequencies is significant, but still, dicentric contain cells were detected, which were a strong indicator for external radiation exposure.

Accidental neutron exposure in a medical setting: a case study.

In May 2016, a new linear accelerator (Linac) was installed at a hospital oncology department. A team of individuals supervised the installation, including a Radiation Oncologist who acted as an independent observer to the installation, calibration, beam data collection and shielding measurements. In order to ensure the shielding was correct, a licensed representative of the Turkish Atomic Energy Authority carried out formal measurements of the gamma and neutron dose rates at a variety of locations in and around the Linac facility. At 18 MV, the maximum neutron dose rate was 172µSv h-1and the maximum gamma dose rate was approximately 2µSv h-1(ambient dose equivalent in both cases), significantly higher than the expected and local background doses. As the neutron dose rates in particular were so high, it was concluded that the shielding was not sufficient, potentially due to an inadequate design. In order to rule out overexposure during the installation, biological dosimetry was carried out for a number of the individuals involved. The estimated doses were closely aligned with the doses measured using commercially available neutron dosemeters and were also within the tolerance dose ranges estimated using Monte Carlo simulations, which also supported the investigation. The results underline the need for careful planning before and after installation of new radiation exposure facilities, especially high MV Linac operation for which photo-neutrons might need to be mitigated. The results clearly indicate the importance of such checks, in addition to demonstrating the relevance of biological dosimetry supported by modelling strategies complex or unclear exposure scenarios.

UNCERTAINTY ON RADIATION DOSES ESTIMATED BY BIOLOGICAL AND RETROSPECTIVE PHYSICAL METHODS.

Biological and physical retrospective dosimetry are recognised as key techniques to provide individual estimates of dose following unplanned exposures to ionising radiation. Whilst there has been a relatively large amount of recent development in the biological and physical procedures, development of statistical analysis techniques has failed to keep pace. The aim of this paper is to review the current state of the art in uncertainty analysis techniques across the 'EURADOS Working Group 10-Retrospective dosimetry' members, to give concrete examples of implementation of the techniques recommended in the international standards, and to further promote the use of Monte Carlo techniques to support characterisation of uncertainties. It is concluded that sufficient techniques are available and in use by most laboratories for acute, whole body exposures to highly penetrating radiation, but further work will be required to ensure that statistical analysis is always wholly sufficient for the more complex exposure scenarios.