Skin dose contamination conversion coefficients. Benchmark with three simulation codes.

Handling of radioactive material by operators can lead to contamination at the surface of the skin in case of an accident. The quantification of the dose received by the skin due to a contamination scenario is performed by means of dedicated dose coefficients as it is the case for other radiation protection dose quantities described in the literature. However, most available coefficients do not match realistic scenarios according to state-of-the-art of science and technology. Therefore, this work deals with dedicated dose conversion factors for skin contamination. Since there is an increasing demand on dose coefficients in general, these specific coefficients can be used for various calculations in radiation protection. In this work a method to evaluate such coefficients for the skin contamination dose related to photons, electrons, positrons, alpha and neutron particles is proposed. The coefficients are generated using Monte-Carlo simulations with three well established calculation codes (FLUKA, MCNP, and GEANT4). The results of the various codes are compared against each other for benchmarking purposes. The new dose coefficients allow the computation of the skin received dose, in the case of skin contamination scenario of an individual, taking into account the decay radiation of the radionuclides of interest. To benchmark the quantity derived here, comparisons of radionuclide contamination doses to the skin using the VARSKIN code available in the literature are performed with the results of this work.

Photons fluence to local skin Dose coefficients and benchmark with three Monte-Carlo codes. Application to the computation of radioactive material transport limits.

Fluence to Local Skin Dose Conversion Coefficients (LSD-CC) are radiological protection quantities used for external radiation exposures which allow the conversion of particle fluences into local skin equivalent dose. The International Commission on Radiological Protection published LSD-CC for electrons with an energy range from 10 keV to 10 MeV. However, the literature does not address these radiation protection quantities for all particle types, in particular for photons. In this article, computed LSD-CC values for photons are presented which enrich the literature and are of interest for the radiation protection community. As an example for an application of the use of the computed LSD-CC values, the IAEA A1/A2 working group, which supports the review of the international regulation related to the transport of radioactive material, has decided to estimate the dose to the skin using such coefficients. In this publication, LSD-CC for photons are computed and benchmarked using GEANT4, FLUKA and MCNP. In addition, the FLUKA Monte-Carlo calculation code is used to compute the LSD-CC values for electrons and positrons to compare with existing data in the literature and validate the presented models. As one application of these LSD-CC values, the transfer functions for calculating the IAEA A-values are determined using the LSD-CC and are compared to a one-step direct calculation method.

Influence of Helicobacter pylori infection and omeprazole treatment on gastric regional CO2.

BACKGROUND: Gastric regional CO(2) accumulation indicates gastric mucosal hypoperfusion in critically ill patients. CO(2) is also a reaction product of urea degradation, and we therefore tested the hypothesis if regional pCO(2) is influenced by Helicobacter pylori infection. MATERIAL: Seven H. pylori-positive and 7 H. pylori-negative volunteers (age range 21-30 years) were investigated. During a 6- to 7-hour observation period, we obtained every 30 min arterial blood gases, gastric juice pH from a glass pH electrode and regional pCO2 from a gastric tonometer. The study protocol included subsequent periods of baseline measurements, pentagastrin stimulation (0.6 microg/kg/h/i.v.) and application of omeprazole (40 mg i.v.). RESULTS: Gastric regional pCO(2) was increased in H. pylori-positive versus H. pylori-negative subjects before (64.4 +/- 3.1 vs. 50.0 +/- 2.9 mm Hg, p < 0.005) but not after application of omeprazole. The effect of omeprazole on gastric juice pH was increased in H. pylori-positive subjects (mean pH during 4 h 6.1 +/- 0.3 in H. pylori-positive vs. 2.5 +/- 0.2 in H. pylori-negative subjects; p < 0.0001). There was a difference in arterial pCO(2) between H. pylori-positive and H. pylori- negative subjects (43.1 +/- 0.3 versus 38.9 +/- 0.3 mm Hg; p < 0.0001). CONCLUSION: H. pylori infection has a significant effect on gastric regional CO(2) that is suppressed by application of a proton pump inhibitor.