SEED: An Operational Numerical Tool for Dosimetric Reconstruction in Case of External Radiological Overexposure

ABSTRACT

In the event of a radiological accident involving external exposure of one or more victims and potential high doses, it is essential to know the dose distribution within the body in order to sort the victims according to the severity of the irradiation and then to take them to the most suitable medical facilities. However, there are currently few techniques that can be rapidly deployed on field and capable of characterizing an irradiation. Therefore, a numerical simulation tool has been designed. It can be implemented by a doctor/physicist pairing, projected within a limited time as close as possible to the irradiation accident and emergency response teams. Called SEED (Simulation of External Exposures & Dosimetry), this tool (dedicated to dose reconstruction in case of external exposure) allows a rapid modeling of the irradiation scene and a visual exchange with the victims and witnesses of the event. The user can navigate in three dimensions in the accident scene thanks to a graphical user interface including a "first person" camera. To validate the performance of the SEED tool, two dosimetric benchmarking exercises were performed. The first consisted in comparing the dose value provided by SEED to that given by a reference calculation code: MCNPX. The purpose of the second validation was to perform an experiment irradiating a physical dummy equipped with dosimeters and to reconstruct this irradiation using SEED. These two validation protocols have shown satisfactory results with mean difference less than 2% and 12% for the first and second exercises, respectively. They confirm that this new tool is able to provide useful information to medical teams in charge of dosimetric triage in case of a major external exposure event.

Deployment of the DosiKit System Under Operational Conditions: Experience From a French Defense National Nuclear Exercise

Estimation of the dose received by accidentally irradiated victims is based on a tripod: clinical, biological, and physical dosimetry. The DosiKit system is an operational and mobile biodosimetry device allowing the measurement of external irradiation directly on the site of a radiological accident. This tool is based on capillary blood sample and hair follicle collection. The aim is to obtain a whole-body and local-surface dose assessment. This paper is about the technical evaluation of the DosiKit; the analytical process and scientific validation are briefly described. The Toulon exercise scenario was based on a major accident involving the reactor of a nuclear attack submarine. The design of the scenario made it impossible for several players (firefighters, medical team) to leave the area for a long time, and they were potentially exposed to high dose rates. The DosiKit system was fully integrated into a deployable radiological emergency laboratory, and the response to operational needs was very satisfactory.

Missions of the French Defense Radiation Protection Service Concerning The Medical Management of Radio-contaminated Patients

The French Defense Radiation Protection Service (SPRA) is an institution of the French Armed Forces (SSA) that provides technical support in radiation protection matters for French military units. It provides services for the armed forces and when necessary for the national public health system. The aim of this note is to describe the variety of services provided by the SPRA in France and abroad, not only in a military context but also in the broader field of radiation protection.

[Role of electroencephalography in the diagnosis of acute cerebral diseases]

It appears from a study of 100 cases of acute cerebral disease that electroencephalography is valuable as part of the diagnosis strategy and not only to establish the correct final diagnosis. This examination therefore plays a non-negligible role in neurological practice. In a number of diseases it provides information that no other examination can provide, being a dynamic, functional method of brain tissue analysis.

Transverse topographical analysis of petit mal discharges: diagnostical and pathogenic implications

The analysis, so far neglected, of the transverse distribution of the paroxysmal bilaterally synchronous activities (PBSA) of petit mal leads to differentiate two topographical varieties of discharges: a lateral variety, where the spike-and-wave patterns present two symmetrical maxima one on each side of the skull, and a medial variety, where the paroxysmal activity exhibits a maximal voltage on the midsagittal area of the scalp. In both cases the EEG patterns involve the frontal areas. In a group of 46 children, referred for petit mal, we have studied 3 main clinical parameters: the symptomatology of the absence, the evolution and the associations of the disease. This study results in the individualization of two forms of petit mal: (1) one marked by lateral discharges, simple absences, a good prognosis and non-specific associations with other epilepsies; (2) the other by medial discharges, complex absences, a poor prognosis and a high rate of associations with other forms of generalized epilepsies. The discussion is devoted to the pathogenic implications of the transverse topographical analysis of the PBSA of petit mal and more generally of bilaterally synchronous activities, paroxysmal or not, expressing physiological or pathological processes.

[Topographical distribution of EEG activity induced by anesthetic agents]

Having noticed in a wide series of subjects submitted to prolonged anaesthesia that the EEG activities induced by anaesthetic products exhibited transverse topographic distributions (preferentially medial or preferentially lateral) which varied in relation to the product utilised, the authors have verified, in a more limited series of 25 subjects, that benzodiazepines, the targets of which are situated within the axial structures of the CNS, are responsible for EEG modifications which show a maximal amplitude on the parasagittal medial area of the scalp, while propanidide, which mainly affects the cortex of the convexity (i.e. the superior level of the lateral structures of the CNS), induces activities which show a maximal amplitude on the lateral areas of the scalp. The EEG modifications induced by thiopental and fentanyl are also lateralized but more diffuse. These data must be verified by a more precise study of a larger series, taking into account the dose and the speed of injection of the anaesthetic agent.

[Study on focalized EEG paroxysms in children (author's transl)]

The authors studied 111 children whose EEG showed paroxysmal foci on the lateral areas of the skull, often on the rolandic and temporal areas, but also on occipital, parietal and frontal areas. In 60% of the cases there was no clinical epileptic manifestation. In 25% of the cases those foci were responsible for epileptic seizures with good prognosis; in 15% of the cases they were associated with other epileptogenic processes responsible for epileptic fits of unfavorable evolution. The past history of these children had been studied in particular: hyperthermic convulsions and lateralisation difficulties were very frequent, but organic lesions were also found, which, although they did not seem to be directly responsible for the foci, were related to the organic lesion by a reactional or 'functional' factor.

[Study of the transversal repartition of the electrical field of paroxysmal discharges in petite mal epilepsies (author's transl)]

A precise analysis of the topography of the EEG critical discharges of Petit Mal, permits a description of two principal varieties, depending whether their electrical field presents two lateral and symmetrical peaks--usually on frontal areas--('lateral variety') or one peak on the mediosagittal line ('medial variety') of the scalp. The relationship which exists between the lateral distribution of EEG discharges and the 'simple' aspect of the absences, on the one hand, and the medial distribution with the 'complex' aspect, on the other, is so close that one is led to hypothesize two distinct epileptogenic processes.