Patient-specific biokinetics and hybrid 2D/3D approach integration in OEDIPE software: Application to radioiodine therapy.

BACKGROUND: The progression of targeted radionuclide therapy requires the development of dosimetry software accounting for patient-specific biokinetics. New functionalities were thus developed in the OEDIPE software, to deal with multiple 3D images or multiple planar images and a SPECT image. MATERIEL & METHOD: Methods were implemented to recover patient biokinetics in volumes of interest. If several 3D SPECT images are available, they are registered to a reference CT scan. When several planar images and a single SPECT are available, the planar images are registered to the SPECT and counts of the planar images converted to activity. To validate these developments, six SPECT/CT and planar images of a Jaszczak phantom containing I-131 were acquired at different dates. Cumulated activity was estimated in each sphere using the SPECT/CT images only or the planar series associated to one SPECT/CT. Biokinetics and doses in lesions and in the lungs of a patient treated with I-131 for differentiated thyroid cancer were then estimated using four planar images and a SPECT/CT scan. Whole-body retention data were used to compare the biokinetics obtained from the planar and SPECT data. 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 compared well with those derived from whole-body retention data. CONCLUSION: The implemented features allow automatic evaluation of patient-specific biokinetics from different series of patient images, enabling patient-specific dosimetry without the need for external software to estimate the cumulated activities in different VOIs.

Evidence for a differential translocation of actinides across human lung epithelial cell monolayer in vitro according to their physicochemical properties and the presence of a chelating agent.

The epithelial cell plays a key role in the transfer of radionuclides from lungs to blood following pulmonary exposure. The present study was designed to evaluate the transfer across human lung epithelial cells of various actinides (plutonium, americium and uranium), the influence of the physicochemical properties of plutonium compounds and of the chelating agent diethylene triamine pentaacetic acid (DTPA). To address this question, Calu-3 cells grown in a bicameral culture system were used. The integrity of the epithelial barrier was evaluated by measuring transepithelial electrical resistance (TEER) and the passage of a fluorescent marker, lucifer yellow. Activity measurement in basal compartment following periodic collection of culture medium was made from 2 h to seven days. To facilitate data handling and analysis, the statistical tool STATBIODIS was used. The results indicate differences in transfer for the different elements, and according to Pu physicochemical properties. Though to various extents, the chelating agent DTPA always increased the transfer of Pu and Am across the epithelial cells, without altering the integrity of the epithelial barrier. This in vitro cell culture model, by mimicking translocation of actinides from lungs to blood, can represent a valuable tool to further understand the underlying mechanisms and properties controlling this process.

Actinide-contaminated Skin: Comparing Decontamination Efficacy of Water, Cleansing Gels, and DTPA Gels.

Skin contamination by alpha-emitting actinides is a risk to workers during nuclear fuel production and reactor decommissioning. Also, the list of items for potential use in radiological dispersal devices includes plutonium and americium. The actinide chemical form is important and solvents such as tributyl phosphate, used to extract plutonium, can influence plutonium behavior. This study investigated skin fixation and efficacy of decontamination products for these actinide forms using viable pig skin in the Franz cell diffusion system. Commonly used or recommended decontamination products such as water, cleansing gel, diethylenetriamine pentaacetic acid, or octadentate hydroxypyridinone compound 3,4,3-LI(1,2-HOPO), as well as diethylenetriamine pentaacetic acid hydrogel formulations, were tested after a 2-h contact time with the contaminant. Analysis of skin samples demonstrated that more plutonium nitrate is bound to skin as compared to plutonium-tributyl phosphate, and fixation of americium to skin was also significant. The data show that for plutonium-tributyl phosphate all the products are effective ranging from 80 to 90% removal of this contaminant. This may be associated with damage to the skin by this complex and suggests a mechanical/wash-out action rather than chelation. For removal of americium and plutonium, both Trait Rouge cleansing gel and diethylenetriamine pentaacetic acid are better than water, and diethylenetriamine pentaacetic acid hydrogel is better than Osmogel. The different treatments, however, did not significantly affect the activity in deeper skin layers, which suggests a need for further improvement of decontamination procedures. The new diethylenetriamine pentaacetic acid hydrogel preparation was effective in removing americium, plutonium, and plutonium-tributyl phosphate from skin; such a formulation offers advantages and thus merits further assessment.

Risk of treatment-related esophageal cancer among breast cancer survivors.

BACKGROUND: Radiotherapy for breast cancer may expose the esophagus to ionizing radiation, but no study has evaluated esophageal cancer risk after breast cancer associated with radiation dose or systemic therapy use. DESIGN: Nested case-control study of esophageal cancer among 289 748 ≥5-year survivors of female breast cancer from five population-based cancer registries (252 cases, 488 individually matched controls), with individualized radiation dosimetry and information abstracted from medical records. RESULTS: The largest contributors to esophageal radiation exposure were supraclavicular and internal mammary chain treatments. Esophageal cancer risk increased with increasing radiation dose to the esophageal tumor location (P(trend )< 0.001), with doses of ≥35 Gy associated with an odds ratio (OR) of 8.3 [95% confidence interval (CI) 2.7-28]. Patients with hormonal therapy ≤5 years preceding esophageal cancer diagnosis had lower risk (OR = 0.4, 95% CI 0.2-0.8). Based on few cases, alkylating agent chemotherapy did not appear to affect risk. Our data were consistent with a multiplicative effect of radiation and other esophageal cancer risk factors (e.g. smoking). CONCLUSIONS: Esophageal cancer is a radiation dose-related complication of radiotherapy for breast cancer, but absolute risk is low. At higher esophageal doses, the risk warrants consideration in radiotherapy risk assessment and long-term follow-up.

SU-E-I-40: Effective Dose Normalized to Dose Length Product for Pediatric and Adult Reference Phantoms in Computed Tomography Examinations.

PURPOSE: To develop a set of conversion factors from dose length product (DLP) to effective dose (E) for pediatric and adult reference individuals undergoing computed tomography (CT) examinations. METHODS: This study used 12 hybrid computational phantoms representing reference pediatric and adult individuals in compliance with the International Commission on Radiological Protection (ICRP) reference data. The phantoms were combined with a model of the Siemens Sensation 16 scanner, to compute organ doses from CT examinations using a radiation transport code, MCNPX2.7. Effective doses based on ICRP 60 and 103 tissue weighting factors were calculated. The DLP was derived from the scan length and Computed Tomography Dose Index (CTDI)vol. The resulting DLP-to-E conversion factors were analyzed. RESULTS: The results consist in a set of DLP-to-E conversion factors for head, chest, abdomen, abdomen-pelvis, and chest-abdomen-pelvis CT examinations for newborn, 1-, 5-, 10-, 15-year-old and adult reference phantoms, for 80, 100 and 120 kVp and for ICRP 60 and 103 tissue weighting factors. The DLP-to-E factors decrease with smaller tube potential, with the greatest decrease for the head examinations for which values at 80 kVp are 20% smaller than at 120 kVp on average. The ICRP 103 weighting factors, compared to ICRP 60, Result in variations of DLP-to-E from 0.8 to 1.2-fold with a systematic increase for the chest, 1.14- fold on average, due to the increased breast weighting factor. The DLP-to-E factors for the body examinations are relatively similar to each other but 5 to 12-fold higher than for the head exam. The factors decrease with age until 15 years and then slightly increase for adult except for head. CONCLUSIONS: An updated set of DLP-to-E conversion factors were established based on more realistic human phantoms and provide an improved accuracy to obtain effective dose from DLP for patients undergoing CT examinations.

Analytical and Monte Carlo assessment of activity and local dose after a wound contamination by activation products.

The activity and local dose following a right index finger wound contamination by activation products are assessed. Measurements with a high purity germanium detector and a four positions measurement protocol enabled a better localization of the contaminant source. From the source location and detector calibration, the remaining wound activity and local absorbed dose were deduced. An analytical model, based on a two dimensional simplification of the problem, is presented. It is shown to provide a fast and quite accurate activity assessment when the contaminants are described as a point source. The contaminants' location and activity were then more accurately assessed using Monte Carlo calculations based on the OEDIPE software and a voxelized phantom of the index finger. Describing the contaminant mixture as a point source resulted in an agreement of experimental and computed data around 6% for most of the radionuclides. The total activity, due to 11 radionuclides, was estimated to be (9.5 +/- 0.4) kBq at measurement day. Since the point source is found to be less than 1 mm under the skin, the equivalent skin dose is calculated and found to be around 680 mSv in the first year after the contamination, and this value decreases to 250 mSv in the second year. The relevance of equivalent skin dose as an estimate of the sanitary risk is discussed, and it is concluded that for this case it gives the upper end estimate of the risk.

OEDIPE: a new graphical user interface for fast construction of numerical phantoms and MCNP calculations.

Although great efforts have been made to improve the physical phantoms used to calibrate in vivo measurement systems, these phantoms represent a single average counting geometry and usually contain a uniform distribution of the radionuclide over the tissue substitute. As a matter of fact, significant corrections must be made to phantom-based calibration factors in order to obtain absolute calibration efficiencies applicable to a given individual. The importance of these corrections is particularly crucial when considering in vivo measurements of low energy photons emitted by radionuclides deposited in the lung such as actinides. Thus, it was desirable to develop a method for calibrating in vivo measurement systems that is more sensitive to these types of variability. Previous works have demonstrated the possibility of such a calibration using the Monte Carlo technique. Our research programme extended such investigations to the reconstruction of numerical anthropomorphic phantoms based on personal physiological data obtained by computed tomography. New procedures based on a new graphical user interface (GUI) for development of computational phantoms for Monte Carlo calculations and data analysis are being developed to take advantage of recent progress in image-processing codes. This paper presents the principal features of this new GUI. Results of calculations and comparison with experimental data are also presented and discussed in this work.

Automatic application of ICRP biokinetic models in voxel phantoms for in vivo counting and internal dose assessment.

As part of the improvement of calibration techniques of in vivo counting, the Laboratory of Internal Dose Assessment of the Institute of Radiological Protection and Nuclear Safety has developed a computer tool, 'OEDIPE', to model internal contamination, to simulate in vivo counting and to calculate internal dose. The first version of this software could model sources located in a single organ. As the distribution of the contamination evolves from the time of intake according to the biokinetics of the radionuclide, a new facility has been added to the software first to allow complex heterogeneous source modelling and then to automatically integrate the distribution of the contamination in the different tissues estimated by biokinetic calculation at any time since the intake. These new developments give the opportunity to study the influence of the biokinetics on the in vivo counting, leading to a better assessment of the calibration factors and the corresponding uncertainties.