Analysis methodology and development of a statistical tool for biodistribution data from internal contamination with actinides

International audienceThe aim of this work was to develop a computational tool that integrates several statistical analysis features for biodistribution data from internal contamination experiments. These data represent actinide levels in biological compartments as a function of time and are derived from activity measurements in tissues and excreta. These experiments aim at assessing the influence of different contamination conditions (e.g. intake route or radioelement) on the biological behavior of the contaminant. The ever increasing number of datasets and diversity of experimental conditions make the handling and analysis of biodistribution data difficult. This work sought to facilitate the statistical analysis of a large number of datasets and the comparison of results from diverse experimental conditions. Functional modules were developed using the open-source programming language R to facilitate specific operations: descriptive statistics, visual comparison, curve fitting, and implementation of biokinetic models. In addition, the structure of the datasets was harmonized using the same table format. Analysis outputs can be written in text files and updated data can be written in the consistent table format. Hence, a data repository is built progressively, which is essential for the optimal use of animal data. Graphical representations can be automatically generated and saved as image files. The resulting computational tool was applied using data derived from wound contamination experiments conducted under different conditions.In facilitating biodistribution data handling and statistical analyses, this computational tool ensures faster analyses and a better reproducibility compared with the use of multiple office software applications. Furthermore, re-analysis of archival data and comparison of data from different sources is made much easier. Hence this tool will help to understand better the influence of contamination characteristics on actinide biokinetics. Our approach can aid the optimization of treatment protocols and therefore contribute to the improvement of the medical response after internal contamination with actinides

Skin absorption of actinides: influence of solvents or chelates on skin penetration ex vivo

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Patient-specific biokinetics evaluation based on multiple SPECT images or hybrid planar/SPECT technique using OEDIPE 3D personalized dosimetry software: development and application

International audienceBackground:With the development of targeted radionuclide therapy, it has become increasingly necessary to develop comprehensive tools to compute 3D personalized dosimetry accounting for patient-specific biokinetics. For that purpose new functionalities were developed in OEDIPE software, to insure compatibility with different sets of patient images (multiple 3D images, multiple planar/SPECT images).Materiel & Method:Two new processes of image analyses were implemented and adapted to multiple time-point 3D images (SPECT/CT or PET/CT), and multiple planar images associated to a single SPECT/CT. Both processes enable recovering time-activity data for each volume of interest (VOI). A biokinetic module was developed to fit time-activity curves (TACs) to the obtained data and to calculate the cumulated activity in the VOIs. To evaluate the robustness of these developments, multiple SPECT/CT and planar images of a JASZCZAK phantom containing I-131 were consecutively acquired at different time-points. Cumulated activity of I-131 was estimated in each sphere using: (i) the SPECT/CT images only, and (ii) the planar series associated to one SPECT/CT out of the six available images, to quantify the influence of the selected time-point at which the SPECT was acquired. Results were compared with the known cumulated activity. To test the clinical applicability of these developments, cumulated activities in lesions and in the lungs of a patient treated for differentiated thyroid cancer were estimated using four planar images and a SPECT/CT scan acquired after I-131 administration. Whole-body retention data combined with SPECT activities were used to generate biokinetic data to compare with.Results:Activities and cumulated activities estimated using OEDIPE in the phantom spheres agreed well with the reference values for both approaches. Results obtained for the patient were similar with those derived from the method based on the whole-body retention data combined with SPECT activities.Conclusion:These new features of OEDIPE allow automatic evaluation of patient-specific biokinetics from different series of patient images, enabling efficient patient-specific internal dosimetry without the need for external software to estimate the cumulated activities in different VOIs.Keywords:targeted radionuclide therapy (TRT); radiopharmaceutical therapy (RPT); patient-specific biokinetics; 3D personalized internal dosimetry; Monte Carlo-based radiation transport code; OEDIPE dosimetric software; hybrid planar-SPECT dosimetr

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

<div><p>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.</p></div