Assessment of the potential impact of embedded radioactive fragments following the use of a crude radiological dispersal device ('dirty bomb')

This work was undertaken to understand what would happen if a high-activity radioactive fragment became embedded in an individual following the use of a crude radiological dispersal device ('dirty bomb'). Two areas were addressed: how would a high-activity fragment be viewed on modern digital x-ray imaging systems; and, what would be the impact on medical management for the patient? A set of experimental trials were undertaken using an iridium-192 source and a DRagon mobile x-ray set equipped with a Canon CXDI-50G portable flat panel digital detector plate. In addition, the potential doses to a surgical team were calculated and potential doses to a patient were assessed using a Monte Carlo code, in which a radioactive point source of nil volume was located within a limb of an anthropomorphic voxel phantom. Three distinct effects on the digital imaging systems were observed, referred to in this paper as a localised 'bloom' effect, a 'discontinuity' effect towards the middle of the image and 'fogging' across the entire image. The first two of these effects were unexpected, and possible reasons for their appearance are discussed. The Monte Carlo modelling showed that the patient exposure can potentially lead to very high localised absorbed doses, which may result in symptoms associated with acute radiation syndrome. While the dose clearly depends upon the activity of the fragment and the length of time that the fragment is present inside the patient, it is clear that radiation necrosis of bone, muscle and other tissues may threaten the medium term viability of the limb. The dose rates associated with high-activity fragments may also restrict the time a surgeon has to operate, leading to challenging ethical and surgical decisions. Low-activity fragments allow for conventional surgical management to be considered with appropriate control measures.