Within the ORAMED project (Optimization of Radiation Protection of Medical Staff) a coordinated measurement program for occupationally exposed medical staff was performed in different hospitals in ...Europe (
www.oramed-fp7.eu). The main objective was to obtain a set of standardized data on extremity and eye lens doses for staff involved in interventional radiology and cardiology and to optimize radiation protection. Special attention was given to the measurement of the doses to the eye lenses. In this paper an overview will be given of the measured eye lens doses and the main influence factors for these doses. The measured eye lens doses are extrapolated to annual doses. The extrapolations showed that monitoring of the eye lens should be performed on routine basis.
► Eye lens dose limit of 150 mSv is generally not reached in IR/IC. ► Monitoring of eye lens dose is recommended (except for ERCP) in IR/IC. ► New eye lens dose limit of 20 mSv will be surpassed by many physicians in IR/IC.
Report Committee 26 of the ICRU proposes a set of operational quantities for radiation protection for external radiation, directly based on effective dose and for an extended range of particles and ...energies. It is accompanied by quantities for estimating deterministic effects to the eye lens and the local skin. The operational quantities are designed to overcome the conceptual and technical shortcomings of those presently in use. This paper describes the proposed operational quantities, and highlights the improvements with respect to the present, legal monitoring quantities.
Due to the recent new interest of the dosimetric community generated by evidence of larger number of induced cataracts for the same absorbed dose, in the frame work of the ORAMED project (
Oramed, ...2008) a task was devoted to the critical revision of the eye lens dose assessment procedures. The present paper summarizes the Monte Carlo analyses carried out to optimize the
H
p(3,Ω) calculations in order to produce a set of conversion coefficients
H
p(3,Ω)/
K
a as close as possible to those of the limiting quantity
H
T(eye lens)/
Ka. Comparison were carried out with already published values calculated for a previous theoretical phantom, mainly suited for the calculations of
H
p(10,Ω)/
K
a.
► The paper presents a critical revision of eye lens dosimetry issues. ► A proposal of a new cylindrical phantom, close to the head shape, was formulated. ► The theoretical phantom is suited to calculate new conversion coefficients for eye lens exposures. ► Monte Carlo was employed for the calculations vs photon energy and incident angle. ► A corresponding plastic water filled calibration phantom was designed.
The increasing demand of rapid and reliable experimental techniques for the dosimetric characterization of high-intensity neutron fields, as those produced by radiotherapy and radioisotope ...installations, is the main reason for this study. In the past years INFN implemented a Bonner Sphere System, equipped with TLDs or gold activation foils, which was successfully employed for neutron spectra measurements around medical LINACs. The INFN–ENEA collaboration extended this methodology to Dysprosium activation foils. Taking advantage of the high activation cross section (2700 barn at 0.025 eV), the photon insensitivity and the reasonably short half live (2.334 h), the Dy-based BSS (Dy-BSS) is highly suited for operational measurements, where short irradiations and short measurement times are desirable. This work presents the response matrix of the Dy-BSS, calculated with MCNPX, and the results of its experimental validation, performed with reference neutron fields at the ENEA-Bologna labs. In addition, the newly developed Dy-BSS and the traditional gold foil-based BSS are compared, underlying the advantages of the new system.
In recent years voxel phantoms have been developed on the basis of tomographic data of real individuals allowing new sets of conversion coefficients to be calculated for effective dose. Progress in ...radiation studies brought ICRP to revise its recommendations and a new report, already circulated in draft form, is expected to change the actual effective dose evaluation method. In the present paper the voxel phantom NORMAN developed at HPA, formerly NRPB, was employed with MCNP Monte Carlo code. A modified version of the phantom, NORMAN-05, was developed to take into account the new set of tissues and weighting factors proposed in the cited ICRP draft. Air kerma to organ equivalent dose and effective dose conversion coefficients for antero-posterior and postero-anterior parallel photon beam irradiations, from 20 keV to 10 MeV, have been calculated and compared with data obtained in other laboratories using different numerical phantoms. Obtained results are in good agreement with published data with some differences for the effective dose calculated employing the proposed new tissue weighting factors set in comparison with previous evaluations based on the ICRP 60 report.
The recent statement on tissue reactions issued by the International Commission on Radiological Protection in April 2011 recommends a very significant reduction in the equivalent dose annual limit ...for the eye lens from 150 to 20 mSv y(-1); this has stimulated a lot of interest in eye lens dosimetry in the radiation protection community. Until now no conversion coefficients were available for the operational quantity Hp(3) for neutrons. The scope of the present work was to extend previous evaluations of H*(10) and Hp(10) performed at the PTB in 1995 to provide also Hp(3) data for neutrons. The present work is also intended to complete the studies carried out on photons during the last 4 y within the European Union-funded ORAMED (optimisation of radiation protection for medical staff) project.
Since the first developments of Monte Carlo radiation transport codes, the importance of solving deep penetration problems in the phase space was pointed out. Whilst natural Monte Carlo radiation ...transport models are rather easy and straightforward to be implemented, apart from geometry extreme complexities that could limit the modelling capabilities of the user, the possibility to obtain results with high precision and reasonable CPU time, when the scored events contributing to the response of interest are characterised by a low probability of occurrence, can be guaranteed only through biased games for which the user needs a robust expertise. The present paper wanted to present in a concise way the main aspects of the variance reduction techniques and some practical application to help the users in becoming more familiar with such a necessary tool.
The ORAMED (Optimization of RAdiation protection for MEDical staff) Working Tasks (WP4) is addressed at evaluating extremity doses (and dose distributions across the hands) of medical staff working ...in nuclear medicine departments, to study the influence of protective devices such as syringe and vial shields, to improve such devices when possible and to propose “levels of reference doses” for each standard nuclear medicine procedure.
In particular task 4 is concerned with the study of the extremity dosimetry for the hand of operators devoted to the preparation and administration stages of the usage, for example, of
99mTc,
18F and
90Y (Zevalin) radionuclides.
The aim of this report consists in the study of photon-electron equilibrium conditions at 0.07 mm in the skin to justify a simplified “kerma approximation” approach in the planned complex Monte Carlo voxel hand modeling. Furthermore a detailed investigation on primary electron and secondary bremsstrahlung photon transport from
90Y to speed up the calculations was performed.
The results obtained in the simplified investigated conditions could be of help for the production calculations, introducing, if necessary, suited correction factors applicable to the complex condition results.
The work package two of the ORAMED project--Collaborative Project (2008-2011) supported by the European Commission within its seventh Framework Programme--is devoted to the study of the eye lens ...dosimetry. A first approach is to implement the use of H(p)(3) by providing new sets of conversion coefficients and well suited calibration and type test procedures. This approach is presented in other papers in the proceedings of this conference. Taking into account that the eye lens is an organ close to the surface of the body, another approach would be to directly estimate the absorbed dose to the eye lens, D(lens,est) through a special calibration procedure although this quantity is not directly measurable. This paper is a methodological paper that tries to identify the critical aspects of a dosimetry in terms of D(lens).