[en] A deformed and energy dependent phenomenological optical model potential and coupled-channel formalism for deformed nuclei have been used in the analysis of elastic and inelastic (Q = 4.439 MeV) scattering, and analyzing power for neutrons scattered from ¹²C in the energy range of 9 to 15 MeV. 6 refs., 1 fig., 1 tab

[en] The authors have tried to reproduce the results of Monte Carlo calculations and experiments with an analytical expression to describe the electron beam central axis depth dose distribution. The overall agreement between fitted and original data for water in the energy range of 1-6-MeV is within 1.5% for all depths down to the RCSDA range (continuous slowing down approximation). Non-linear parameters obtained from fitting Monte Carlo calculated depth doses in copper and aluminium are also presented. (U.K.)

[en] Elastic and inelastic neutron scattering from ¹²C is studied in a coupled-channel approach

[en] Application of radioactive isotopes is the treatment of choice around the globe for many cancer sites. In this technique, the accuracy of the radiation delivery is highly dependent on the accuracy of radiation dosimetry around individual brachytherapy sources. Moreover, in order to have compatible clinical results, an identical method of source dosimetry must be employed across the world. This problem has been recently addressed by task group 43 from the American Association of Medical Physics with a protocol for dosimetric characterization of brachytherapy sources. This new protocol has been further updated using published data from international sources, by a new Task Group from the American Association of Medical Physics. This has resulted in an updated protocol known as TG43U1 that has been published in March 2004 issue of Medical Physics. The goal of this presentation is to review the original Task Group 43 protocol and associated algorithms for brachytherapy source dosimetry. In addition, the shortcomings of the original protocol that has been resolved in the updated recommendation will be highlighted. I am sure that this is not the end of the line and more work is needed to complete this task. I invite the scientists to join this task and complete the project, with the hope of much better clinical results for cancer patients

[en] New measurements of neutron elastic and inelastic scattering from ¹²C are presented and analyzed in terms of a deformed optical model potential. Results of these analyses have been compared with other recent differential and total neutron scattering measurements and with proton scattering data in order to develop a consistent representation of the energy dependence of the n-¹²C interaction over a broad energy range. Applications of the data and the model to problems in neutron dosimetry are discussed

[en] New measurements of differential elastic and inelastic neutron scattering from ¹²C at Esub(n) = 20.8, 22, 24 and 26 MeV are presented and analysed in terms of both spherical and deformed optical model potentials. Results of these analyses are compared with other recent differential and total cross-section measurements in order to obtain a consistent representation of the energy dependence of neutron scattering over a broad energy range. Heavy ion recoil kerma factors are calculated and compared with earlier measurements and estimates of these quantities. (author)

[en] The Ohio University Beam Swinger provides a high resolution, low back-ground time-of-flight facility for the measurement of elastic and inelastic neutron scattering. It has been used to obtain a comprehensive set of differential scattering cross sections for ¹²C, ¹⁴N, ¹⁶O and ⁴⁰Ca between 18 and 26 MeV. The elastic cross sections can be used directly to obtain partial kerma factors and, combined with the known total cross sections, provide accurate values for the reaction cross sections. Angular distributions have been measured for inelastic scattering from all the nuclear levels that cannot decay by particle emission thus providing (by subtraction) a limit on the sum of all charged-particle producing reactions. The integrated cross sections for inelastic scattering from some particle-unstable states in ¹²C are in excellent agreement with the cross sections for three-body breakup obtained by Antolkovic et al. The differential data have been used, together with higher energy proton scattering data to produce energy-dependent optical model parameters for each of these nuclei in the energy range 20-60 MeV. It has been found that the elastic differential cross sections at theta > 100⁰ for ¹²C, ¹⁴N and ¹⁶O cannot be well described by a spherical optical model. Explicit consideration of coupled-channel effects, and in the case of ¹²C, deformation of the ground state, improves the agreement between calculation and experiment. Heavy ion recoil kerma factors and reaction cross sections have been obtained for each element and compared with previous calculations and measurements

[en] Dosimetric characteristics of the BrachySeed^TM Pd-103, Model Pd-1 source have been determined using both theoretical and experimental methods. Dose rate constant, radial dose function, and anisotropy functions of the source have been obtained following the TG-43 recommendations. Derivation of the dose rate constant was based on recent NIST WAFAC calibration performed in accordance with their 1999 Standard. Measurements were performed in Solid Water^TM using LiF TLD chips. Theoretical simulation calculations were performed in both Solid Water^TM and water phantom materials using MCNP4C2 Monte Carlo code using DLC-200 interaction data. The results of the Monte Carlo simulation indicated a dose rate constant of 0.65 cGy h^-1 U^-1 and 0.61 cGy h^-1 U^-1 in water and Solid Water^TM, respectively. The measured dose rate constant in Solid Water^TM was found to be 0.63±7% cGy h^-1 U^-1, which is within the experimental uncertainty of the Monte-Carlo simulated results. The anisotropy functions of the source were calculated in both water and in Solid Water^TM at the radial distances of 1 to 7 cm. Measurements were made in Solid Water^TM at distances of 2, 3, 5, and 7 cm. The Monte-Carlo calculated anisotropy constant of the new source was found to be 0.98 in water. The tabulated data and 5th order polynomial fit coefficients for the radial dose function along with the dose rate constant and anisotropy functions are provided to support clinical use of this source

[en] Dosimetric characteristics of polystyrene, solid water, and polymethylmethacrylate were examined and compared to water to determine the suitability of these solid materials for the dosimetry of ¹⁹²Ir. Ionization charge measured in each of the four media as a function of depth and depth-dose curves calculated by Monte Carlo simulation show that the three solids are equivalent to each other and to water under full scattering conditions. Photon energy spectra generated from the Monte Carlo simulation show little variation for the different media. Mass energy absorption coefficients and exposure-to-dose conversion factors were calculated as a function of depth for these spectra. Measured tissue attenuation factors are in excellent agreement with Meisberger's selected values. The radial dose function, which describes the change in dose with distance in phantom exclusive of the inverse square law, was calculated from the tissue attenuation factor and found to be in significant disagreement with Dale's Monte Carlo values. The reason for this discrepancy is discussed

[en] In this work, dose in polystyrene was measured at several distances from the high activity ¹⁹²Ir source (370GBq) of a remote afterloading device using an ionisation chamber and LiF TLD chips. These data show that over a range of 1-10 cm from the source the sensitivity of LiF varies by up to 8.5%. This is attributed to the higher response of LiF to the lower photon energies, and to the shift of the photon spectrum to lower energies with increasing depth. The sensitivity of LiF to ¹⁹²Ir was also calculated by weighting the energy-dependent response of LiF by the Monte Carlo calculated photon spectra. The calculations give a similar change in sensitivity with distance from the source. (author)