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The article summarises the development of the system of radiation protection quantities used for occupational exposures to external sources throughout the last century. Although the current system generally meets the radiation protection needs quite satisfactorily, this system has often been the target of criticism. Some controversial issues are highlighted in the present paper. The conclusion is that it would be appropriate to undertake a deep review of the current system and suggest the necessary revisions to remove any ambiguities or confusion and address the deficiencies and incoherencies.

Despite its shortcomings and inconsistencies such as using the kerma approximation, the ICRU tissue, which does not really exist and the radiation quality factor Q defined in water, the personal dose equivalent Hp defined in the 1980s remains until now the operational quantity used to assess the effective dose E for external exposure. To help overcome most of these shortcomings and inconsistencies a new operational quantity Hp(30)water to replace Hp(10) is proposed. Fluence-to Hp(30) water conversion coefficients are calculated for photon energies from 0.02 to 10 MeV using the Monte Carlo transport code EGSnrc. Calculations are performed in a water cube phantom using full transport of secondary charged particles. The comparison of the conversion coefficients of Hp(30) and E shows that Hp(30) water can represent a good envelope of E over the whole energy range considered.

Computation of the dose distribution in brachytherapy requires a good knowledge of the geometric and physical characteristics of the sealed sources, as well as the composition of the medium in which it is calculated. Different dose calculation models have been used in practice. The chemical and physical forms of the radionuclide, as well as the shape and thickness of the capsule, influence the dosimetric properties of the source. The air Kerma rate in air is introduced in most treatment planning systems to define the characteristics of the irradiation. This value is measured by the manufacturer and communicated to the physicist via the calibration certificate. It is up to each physicist to control this value before its us e. In general, it will be measured using an ionization chamber for the source itself, in a plane perpendicular to the axis from the source. The present work aims to perform an analytical calculation of the air kerma rate in air using the Sievert integral for filtered extended sources to develop convenient method for quick verification of the dose or the treatment plan. The Sievert integral, is a special function commonly encountered in radiation transport calculations. It accounts for the photon attenuation in the source capsule of the brachytherapy line source. The computed air kerma rate in air will be used with the AAPM TG43 formalism as a convenient quality assurance method for the verification of dose distributions calculated by the treatment planning system for filtered extended sources. The choice of the Sievert integral is motivated by the fact that it takes into account the length of the source, whereas most of the conventional methods for calculating the air kerma rate in air are based on the hypothesis of the point source. The Sievert integral, involves the air kerma rate in air for point source, the active length of the source, the capsule thickness and an effective attenuation coefficient of the capsule. For the purpose of calculation, linear sources are assumed to consist of a number of small elementary point sources, each point source contributing to the total dose at the point of interest. The calculated air kerma rates in air for various extended filtered sources used in brachytherapy shows that the use of Sievert integral reduces the air kerma rate in air values, especially near the sources, compared to those obtained with the assumption of a point source, and to the corresponding quantity measured using a well-type chamber. The significant differences were observed for radial distances less than twice the active length of the sources and they decrease with the radial distance increase. The maximum differences were observed at the immediate neighborhood of the source, and increase with the source length increase.

The objective of this study is to evaluate the precision of dose-calculation computer codes used in our laboratory (PCXMC and PREPARE) for organ dose evaluation. Measurements of entrance and organ dose were performed using ionisation chamber and thermoluminescence dosimetry. To obtain a mean dose of organ, we have used the Rando-Alderson phantom. The results showed that computed and measured doses correlate well (within 28%) in 60% of the samples. The percentage shows that the computed doses correlate with the experimental doses rather well for PCXMC software than PREPARE. Although the two programs are based on the Monte-Carlo method, their calculations differ. PCXMC carries out a simulation of the trajectory of the photon, whereas PREPARE provides interpolated values. Our experimental results are close to the values given by the PCXMC, a program which takes into account the weight, the height of the patient and field dimensions.

Introduction Il s’agit des methodes statistiques utilisant la theorie de l’estimation de signaux dans un milieu bruite. Il est primordial de diminuer la dose administree sans toutefois sacrifier la qualite des images. Clairement, il s’agit dans ce cas d’estimer en vue d’exterieure le signal tres bruite en utilisant des faibles doses. Ces methodes sont toutefois lentes comparativement a la FBP. Notre objectif est a la fois de les accelerer par divers moyens, notamment l’optimisation d’un algorithme de reconstruction iterative, parallelisation d’un algorithme en utilisant l’environnement GPUs… et surtout de proposer de meilleures extractions dans le cas des faibles doses. Methodes et resultats Ce travail porte sur l’implementation sous MATLAB de la retroprojection filtree pour : parallele, Fan et Cone Beam et aussi sur les algorithmes FDK, OSEM et MLEM. Cette implementation a ete appliquee sur le fantome mathematique SHEPP-LOGAN-3D, sur des donnees cliniques disponibles sur le NET (open source), ainsi que sur les projections brutes exploitees de la gamma camera SPECT/CT disponible dans le service de medecine nucleaire/HCA ; acceleration par methode de parallelisation des algorithmes FDK, MLEM et OSEM sur des interfaces graphiques, a savoir les GPUs. Conclusions (1) Implementation et comparaison et differentes methodes de reconstruction pour les deux modalites TDM et SPECT, avec etude de l’impact des differents filtres et effet du bruit sur la qualite d’image. (2) Acceleration des methodes iteratives par methode de parallelisation. (3) Des resultats additionnels seront ajoutes eventuellement au fur et a mesure de l’avancement de ce travail.

We have studied the quasielastic He-3(e,e(')p)H-2 reaction in perpendicular coplanar kinematics, with the energy and the momentum transferred by the electron fixed at 840 MeV and 1502 MeV/c, respectively. The He-3(e,e(')p)H-2 cross section was measured for missing momenta up to 1000 MeV/c, while the A(TL) asymmetry was extracted for missing momenta up to 660 MeV/c. For missing momenta up to 150 MeV/c, the cross section is described by variational calculations using modern He-3 wave functions. For missing momenta from 150 to 750 MeV/c, strong final-state interaction effects are observed. Near 1000 MeV/c, the experimental cross section is more than an order of magnitude larger than predicted by available theories. The A(TL) asymmetry displays characteristic features of broken factorization with a structure that is similar to that generated by available models.

Results of the Jefferson Lab Hall A quasielastic 3He(e,e'p)pn measurements are presented. These measurements were performed at fixed transferred momentum and energy, q=1502 MeV/c and omega=840 MeV, respectively, for missing momenta p(m) up to 1 GeV/c and missing energies in the continuum region, up to pion threshold; this kinematic coverage is much more extensive than that of any previous experiment. The cross section data are presented along with the effective momentum density distribution and compared to theoretical models.

We have studied the quasielastic $^{3}He(e,e'p)^{2}H$ reaction in perpendicular coplanar kinematics, with the energy and the momentum transferred by the electron fixed at 840 MeV and 1502 MeV/c, respectively. The $^{3}He(e,e'p)^{2}H$ cross section was measured for missing momenta up to 1000 MeV/c, while the ATL asymmetry was extracted for missing momenta up to 660 MeV/c. For missing momenta up to 150 MeV/c, the cross section is described by variational calculations using modern 3He wave functions. For missing momenta from 150 to 750 MeV/c, strong final-state interaction effects are observed. Near 1000 MeV/c, the experimental cross section is more than an order of magnitude larger than predicted by available theories. The ATL asymmetry displays characteristic features of broken factorization with a structure that is similar to that generated by available models.

We have studied the quasielastic 3He(e,e(')p)2H reaction in perpendicular coplanar kinematics, with the energy and the momentum transferred by the electron fixed at 840 MeV and 1502 MeV/c, respectively. The 3He(e,e(')p)2H cross section was measured for missing momenta up to 1000 MeV/c, while the A(TL) asymmetry was extracted for missing momenta up to 660 MeV/c. For missing momenta up to 150 MeV/c, the cross section is described by variational calculations using modern 3He wave functions. For missing momenta from 150 to 750 MeV/c, strong final-state interaction effects are observed. Near 1000 MeV/c, the experimental cross section is more than an order of magnitude larger than predicted by available theories. The A(TL) asymmetry displays characteristic features of broken factorization with a structure that is similar to that generated by available models.

Results of the Jefferson Lab Hall A quasielastic 3He(e,e'p)pn measurements are presented. These measurements were performed at fixed transferred momentum and energy, q = 1502 MeV/c and omega = 840 MeV, respectively, for missing momenta p_m up to 1 GeV/c and missing energies in the continuum region, up to pion threshold; this kinematic coverage is much more extensive than that of any previous experiment. The cross section data are presented along with the effective momentum density distribution and compared to theoretical models., Comment: 5 pages, 3 figures, updated to reflect published paper: minor text changes from previous version along with updated and added references