Actinide bioimaging in tissues: Comparison of emulsion and solid track autoradiography techniques with the iQID camera

Abstract

This work presents a comparison of three autoradiography techniques for imaging biological samples contaminated with actinides: emulsion-based, plastic-based autoradiography and a quantitative digital technique, the iQID camera, based on the numerical analysis of light from a scintillator screen. In radiation toxicology it has been important to develop means of imaging actinide distribution in tissues as these radionuclides may be heterogeneously distributed within and between tissues after internal contamination. Actinide distribution determines which cells are exposed to alpha radiation and is thus potentially critical for assessing absorbed dose. The comparison was carried out by generating autoradiographs of the same biological samples contaminated with actinides with the three autoradiography techniques. These samples were cell preparations or tissue sections collected from animals contaminated with different physico-chemical forms of actinides. The autoradiograph characteristics and the performances of the techniques were evaluated and discussed mainly in terms of acquisition process, activity distribution patterns, spatial resolution and feasibility of activity quantification. The obtained autoradiographs presented similar actinide distribution at low magnification. Out of the three techniques, emulsion autoradiography is the only one to provide a highly-resolved image of the actinide distribution inherently superimposed on the biological sample. Emulsion autoradiography is hence best interpreted at higher magnifications. However, this technique is destructive for the biological sample. Both emulsion- and plastic-based autoradiography record alpha tracks and thus enabled the differentiation between ionized forms of actinides and oxide particles. This feature can help in the evaluation of decorporation therapy efficacy. The most recent technique, the iQID camera, presents several additional features: real-time imaging, separate imaging of alpha particles and gamma rays, and alpha activity quantification. The comparison of these three autoradiography techniques showed that they are complementary and the choice of the technique depends on the purpose of the imaging experiment.

Exploiting the “ Rat Actinide Repository “ at the Laboratory of RadioToxicology, CEA, France

“…It is important therefore to consider this when tissues are analysed many years after the actual contamination. More recent experiments using the iQID (ionizing-radiation Quantum Imaging Detector) camera where activity can be measured directly on a tissue section results showed that in lungs from MOX-contaminated rats, higher levels of activity were found in areas of fibrosis as compared with non-fibrotic regions 2 . This technique however has the advantage of being non-destructive and measures activity directly as opposed to dissection and lengthy destructive radiochemical procedures.…”

Enhanced Resolution of Neutron Autoradiography with UV-C Sensitization to Study Boron Microdistribution in Animal Models

“…Due to their versatility and high sensitivity, polymeric NTDs have been extensively used to generate autoradiographies of biological samples for different applications. For example, they have been applied to perform actinide bioimaging in tissues [18] and to determine uranium distribution in rat kidney sections [19]. In the context of BNCT, the autoradiographic image of a histological section coming from a boron-loaded sample is obtained by irradiating the sample-detector assembly with thermal neutrons and later etching to enlarge the particle damage.…”

Comparison of Local and Systemic DTPA Treatment Efficacy According to Actinide Physicochemical Properties Following Lung or Wound Contamination in the Rat

“…The question of the fate of tissue-retained actinides, even initially soluble ones, has been studied particularly with regard to deposition and retention in lungs and eventual effective dose ( International Commission on Radiological Protection(ICRP), 1994a ). Retention compartments in the lungs can be macrophages, interstitial connective tissue as well as scar tissue ( Hahn et al, 2004 ; Van der Meeren et al, 2012 ; Van der Meeren et al, 2014 ; Lamart et al, 2017 ; Birchall et al, 2019 ). Regardless of contaminant solubility (from soluble to insoluble forms such as oxides and metals), retained activity may be considered as a “reservoir”.…”