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A camera for visualizing and quantifying actinide contamination

Researchers at the IRCM and their partner at the University of Arizona compared three imaging tools used to visualize actinides present in contaminated biological tissues. Their analysis provides information on the performance and limitations of each of these autoradiographic techniques. The digital technique is the most recent, and offers certain advantages such as real-time imaging. 

Published on 9 November 2017

It is possible to visualize the radioelements present in contaminated cells, tissues or organs by using autoradiography techniques. Knowing the advantages and limitations of each method is essential for improving the assessment of radiation doses received by living organisms and, ultimately, the monitoring of operators who work at dismantlement sites. 

Researchers from the IRCM’s radiotoxicology laboratory in collaboration with the College of Optical Sciences at the University of Arizona compared 3 autoradiography techniques. The first consists in immersing the contaminated sample in an emulsion of silver ions that are transformed into metallic silver atoms by radiation. The second technique relies on bringing the sample into contact with a plastic film that is sensitive to radiation. The traces left by the radiation are amplified by a chemical solution that etches “holes” on the plastic film. The third technique is digital, and consists of a camera coupled to a scintillation counter. When the counter is excited by ionizing radiation, it emits light that is captured by the camera. 

The researchers used several samples (macrophage, lung, muscle and skin cells) contaminated by different actinides such as plutonium or americium, or a mixture used as fuel in non-military nuclear reactors (MOX). 

The three techniques turn out to be complementary, with different performances in terms of resolution, quantification and acquisition speed. Interestingly, the camera generates images in real time. Thus, it provides a rapid overview of the distribution of contaminants in a tissue, unlike the other two techniques that require long exposures. This feature may be very useful, for example, in analyzing a skin biopsy from someone injured during a dismantling operation, quickly screening numerous contaminated biological samples during a nuclear accident.

A unique sample of macrophage cells circulating in the lungs of a rat having inhaled plutonium oxide was analyzed by three autoradiographic techniques. The exposure times to reveal the radioactivity are as following: 16 hours for the camera (bottom panel), 72 hrs for the plastic detector (middle panel) and one week for the nuclear track emulsion (top panel) © Lamart et al. 

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