Biological in-vivo measurement of dose distribution in patients' lymphocytes by gamma-H2AX immunofluorescence staining: 3D conformal- vs. step-and-shoot IMRT of the prostate gland

<p>Abstract</p> <p>Background</p> <p>Different radiation-techniques in treating local staged prostate cancer differ in their dose- distribution. Physical phantom measurements indicate that for 3D, less healthy tissue is exposed to a relatively higher dose compared to SSIMRT. The purpose is to substantiate a dose distribution in lymphocytes <it>in-vivo </it>and to discuss the possibility of comparing it to the physical model of total body dose distribution.</p> <p>Methods</p> <p>For each technique (3D and SSIMRT), blood was taken from 20 patients before and 10 min after their first fraction of radiotherapy. The isolated leukocytes were fixed 2 hours after radiation. DNA double-strand breaks (DSB) in lymphocytes' nuclei were stained immunocytochemically using the gamma-H2AX protein. Gamma-H2AX foci inside each nucleus were counted in 300 irradiated as well as 50 non-irradiated lymphocytes per patient. In addition, lymphocytes of 5 volunteer subjects were irradiated externally at different doses and processed under same conditions as the patients' lymphocytes in order to generate a calibration-line. This calibration-line assigns dose-value to mean number of gamma-H2AX foci/ nucleus. So the dose distributions in patients' lymphocytes were determined regarding to the gamma-H2AX foci distribution. With this information a cumulative dose-lymphocyte-histogram (DLH) was generated. Visualized distribution of gamma-H2AX foci, correspondingly dose per nucleus, was compared to the technical dose-volume-histogram (DVH), related to the whole body-volume.</p> <p>Results</p> <p>Measured <it>in-vivo </it>(DLH) and according to the physical treatment-planning (DVH), more lymphocytes resulted with low-dose exposure (< 20% of the applied dose) and significantly fewer lymphocytes with middle-dose exposure (30%-60%) during Step-and-Shoot-IMRT, compared to conventional 3D conformal radiotherapy. The high-dose exposure (> 80%) was equal in both radiation techniques. The mean number of gamma-H2AX foci per lymphocyte was 0.49 (3D) and 0.47 (SSIMRT) without significant difference.</p> <p>Conclusions</p> <p><it>In-vivo </it>measurement of the dose distribution within patients' lymphocytes can be performed by detecting gamma-H2AX foci. In case of 3D and SSIMRT, the results of this method correlate with the physical calculated total body dose-distribution, but cannot be interpreted unrestrictedly due to the blood circulation. One possible application of the present method could be in radiation-protection for <it>in-vivo </it>dose estimation after accidental exposure to radiation.</p

EXAFS IN DISPERSIVE MODE, A NEW TOOL FOR STUDYING IN SITU KINETICS : EXAMPLE OF ELECTROCHEMICAL INCLUSION OF COPPER SPECIES IN AN ORGANIC CONDUCTOR

Les mécanismes et les cinétiques d'inclusion électrochimique d'espèces cuivriques dans le poly 3methylthiophène (polymère organique conducteur) ont été étudiés in situ par spectroscopie s'absorption x en mode dispersif. Les mesures EXAFS, complémentaires des résultats déjà obtenus par XANES, permettent de distinguer trois étapes distinctes : - Réduction rapide de Cu2+ en Cu1+ complexé par l'oxygène du dopant utilisé lors de la synthèse du polymère (SO3CF3)- - Fixation des nouveaux ions Cu1+ formés par les atomes de soufre du poly 3methylthiophene - Croissance de plaquettes (111) métalliques de cuivreThe mechanisms and the kinetics for the electrochemical inclusion of copper species inside poly 3methylthiophene (an organic conducting polymer) have been studied in situ by dispersive x ray absorption spectroscopy. The EXAFS results complement the three chemical steps previously deduced from XANES and the nature of chemical bonds formed during the inclusions processes are then precised : - a fast Cu2+ → Cu1+ reduction where the Cu1+ ions are complexed by the O atoms coming from the dopant used during the polymer synthesis (SO3CF3)- - Fixation of the new synthetized Cu1+ ions on the S atoms of poly 3methylthiophene - Growing of (111) metallic copper platelets

SYNCHROTRON RADIATION PLUS PHOTODIODE ARRAY : EXAFS IN DISPERSIVE MODE FOR FAST MICROANALYSIS

L'EXAFS dispersif permet d'obtenir en une seule mesure la totalité d'un spectre EXAFS. L'utilisation de barrettes de photodiode comme détecteur, permet d'utiliser le faisceau intense du rayonnement synchrotron et de réduire ainsi le temps de mesure. Ceci permet des études cinétiques comme dans le cas de la pré-précipitation des alliages Al-Zn.EXAFS in dispersive mode allows one to record simultaneously the whole EXAFS spectrum. The high flux of the synchrotron radiation beam is scanned with photodiode array, which yields short integration times. This allows kinetics studies, as for example the clustering of Al Zn alloys

Spectroscopie résolue dans le temps : études cinétiques in situ de différentes réactions chimiques

La technique d’absorption x en mode dispersif associée à un détecteur à localisation (barrrette de photodiodes) permet d’obtenir des spectres en un temps minimum de 4 ms. De nombreuses études cinétiques ont été réalisées avec ce système, deux exemples sont développés : oxydoréduction d’une électrode d’hydroxide de Nickel et oxygénation et désoxygénation des supraconducteurs haute Tc

ELECTRONIC AND STRUCTURAL MODIFICATIONS OF POLYSELENOPHENE DURING ELECTROCHEMICAL DOPING PROCESS OBSERVED IN SITU BY DISPERSIVE X-RAY ABSORPTION SPECTROSCOPY

The electronic and structural modifications of polyselenophene during the electrochemical doping have been studied by in situ dispersive X-ray absorption spectroscopy. XANES and EXAFS obtained at the C K-edge and the Se K-edge show that i) electrons are extracted from the π bonding band with a modification of the π* band distribution, ii) the Se-Cα bond length increases from 1.885 Å (monomer) to 1.195 Å when the polymer is synthetized, iii) no variation in the C-C and C = C bond length value is observed when polyselenophene is doped in opposition with the bipolaron model and iv) the interaction between the Se atom and the dopant is observed which leads to a reordering of the polymeric chains.Les modifications structurales et electroniques du polyselenophene lors de son dopage electrochimique ont été étudiées in situ à l'aide de la spectroscopie d'absorption X en mode dispersif. Le XANES et l'EXAFS obtenus aux seuils K du carbone et du selenium montrent que i) des electrons sont extraits de la band π liante avec modification de la distribution de la bande π* antiliante, ii) la longueur de la liaison Se-Cα augmente de1.885 Å (pour le monomère) à 1.915 Å lorsque le polymere est synthétisé, iii) aucune variation de longueur pour les liaisons C-C et C = C n'est observée lorsque le polymère est dopé contrairement à ce qui est prévu par le modèle bipolaron et iv) l'interaction entre l'atome de sélénium et le dopant entraîne une réorganisation des chaînes polymériques

HIGH PRESSURE XAS ON BROMINE IN THE DISPERSIVE MODE

Br2 a été étudié sous haute pression par spectroscopie d'absorption X en dispersion d'énergie jusqu'à 57,5 GPa. Les avantages du montage en dispersion d'énergie sont présentés. Les résultats de XANES et d'EXAFS sur le brome sont discutés en termes de dépendance avec la pression de la longueur de la liaison moléculaire et du potentiel interstitiel moyen.High pressure energy dispersive x ray absorption spectroscopy has breen performed on Br2 up to 57.5 GPa. The advantages of the energy disprsive set up are presented. The XANES and EXAFS results on bromine are discussed in terme of bond length and average interstitial potential pressure dependence

Statistical Model for the Orientation of Nonspherical Particles Settling in Turbulence

International audienceThe orientation of small anisotropic particles settling in a turbulent fluid determines some essential properties of the suspension. We show that the orientation distribution of small heavy spheroids settling through turbulence can be accurately predicted by a simple Gaussian statistical model that takes into account particle inertia and provides a quantitative understanding of the orientation distribution on the problem parameters when fluid inertia is negligible. Our results open the way to a parametrization of the distribution of ice crystals in clouds, and potentially lead to an improved understanding of radiation reflection or particle aggregation through collisions in clouds