Efficiency of radiation protection equipment in interventional radiology: a systematic Monte Carlo study of eye lens and whole body doses.

Monte Carlo calculations were used to investigate the efficiency of radiation protection equipment in reducing eye and whole body doses during fluoroscopically guided interventional procedures. Eye lens doses were determined considering different models of eyewear with various shapes, sizes and lead thickness. The origin of scattered radiation reaching the eyes was also assessed to explain the variation in the protection efficiency of the different eyewear models with exposure conditions. The work also investigates the variation of eye and whole body doses with ceiling-suspended shields of various shapes and positioning. For all simulations, a broad spectrum of configurations typical for most interventional procedures was considered. Calculations showed that 'wrap around' glasses are the most efficient eyewear models reducing, on average, the dose by 74% and 21% for the left and right eyes respectively. The air gap between the glasses and the eyes was found to be the primary source of scattered radiation reaching the eyes. The ceiling-suspended screens were more efficient when positioned close to the patient's skin and to the x-ray field. With the use of such shields, the Hp(10) values recorded at the collar, chest and waist level and the Hp(3) values for both eyes were reduced on average by 47%, 37%, 20% and 56% respectively. Finally, simulations proved that beam quality and lead thickness have little influence on eye dose while beam projection, the position and head orientation of the operator as well as the distance between the image detector and the patient are key parameters affecting eye and whole body doses.

Monte Carlo modeling of proton therapy installations: a global experimental method to validate secondary neutron dose calculations.

Monte Carlo calculations are increasingly used to assess stray radiation dose to healthy organs of proton therapy patients and estimate the risk of secondary cancer. Among the secondary particles, neutrons are of primary concern due to their high relative biological effectiveness. The validation of Monte Carlo simulations for out-of-field neutron doses remains however a major challenge to the community. Therefore this work focused on developing a global experimental approach to test the reliability of the MCNPX models of two proton therapy installations operating at 75 and 178 MeV for ocular and intracranial tumor treatments, respectively. The method consists of comparing Monte Carlo calculations against experimental measurements of: (a) neutron spectrometry inside the treatment room, (b) neutron ambient dose equivalent at several points within the treatment room, (c) secondary organ-specific neutron doses inside the Rando-Alderson anthropomorphic phantom. Results have proven that Monte Carlo models correctly reproduce secondary neutrons within the two proton therapy treatment rooms. Sensitive differences between experimental measurements and simulations were nonetheless observed especially with the highest beam energy. The study demonstrated the need for improved measurement tools, especially at the high neutron energy range, and more accurate physical models and cross sections within the Monte Carlo code to correctly assess secondary neutron doses in proton therapy applications.

Secondary neutron doses received by paediatric patients during intracranial proton therapy treatments.

This paper's goal is to assess secondary neutron doses received by paediatric patients treated for intracranial tumours using a 178 MeV proton beam. The MCNPX Monte Carlo model of the proton therapy facility, previously validated through experimental measurements for both proton and neutron dosimetry, was used. First, absorbed dose was calculated for organs located outside the clinical target volume using a series of hybrid computational phantoms for different ages and considering a realistic treatment plan. In general, secondary neutron dose was found to decrease as the distance to the treatment field increases and as the patient age increases. In addition, secondary neutron doses were studied as a function of the beam incidence. Next, neutron equivalent dose was assessed using organ-specific energy-dependent radiation weighting factors determined from Monte Carlo simulations of neutron spectra at each organ. The equivalent dose was found to reach a maximum value of ∼155 mSv at the level of the breasts for a delivery of 49 proton Gy to an intracranial tumour of a one-year-old female patient. Finally, a thorough comparison of the calculation results with published data demonstrated the dependence of neutron dose on the treatment configuration and proved the need for facility-specific and treatment-dependent neutron dose calculations.

Secondary neutron doses in proton therapy treatments of ocular melanoma and craniopharyngioma.

Monte Carlo simulations were used to assess secondary neutron doses received by patients treated with proton therapy for ocular melanoma and craniopharyngioma. MCNPX calculations of out-of-field doses were done for ∼20 different organs considering realistic treatment plans and using computational phantoms representative of an adult male individual. Simulations showed higher secondary neutron doses for intracranial treatments, ∼14 mGy to the salivary glands, when compared with ocular treatments, ∼0.6 mGy to the non-treated eye. This secondary dose increase is mainly due to the higher proton beam energy (178 vs. 75 MeV) as well as to the impact of the different beam parameters (modulation, collimation, field size etc.). Moreover, when compared with published data, the assessed secondary neutron doses showed similar trends, but sometimes with sensitive differences. This confirms secondary neutrons to be directly dependent on beam energy, modulation technique, treatment configuration and methodology.

A correlation study of eye lens dose and personal dose equivalent for interventional cardiologists.

This paper presents the dosimetry part of the European ELDO project, funded by the DoReMi Network of Excellence, in which a method was developed to estimate cumulative eye lens doses for past practices based on personal dose equivalent values, H(p)(10), measured above the lead apron at several positions at the collar, chest and waist levels. Measurement campaigns on anthropomorphic phantoms were carried out in typical interventional settings considering different tube projections and configurations, beam energies and filtration, operator positions and access routes and using both mono-tube and biplane X-ray systems. Measurements showed that eye lens dose correlates best with H(p)(10) measured on the left side of the phantom at the level of the collar, although this correlation implicates high spreads (41 %). Nonetheless, for retrospective dose assessment, H(p)(10) records are often the only option for eye dose estimates and the typically used chest left whole-body dose measurement remains useful.

Radiation protection in digestive endoscopy: European Society of Digestive Endoscopy (ESGE) guideline.

This article expresses the current view of the European Society of Gastrointestinal Endoscopy (ESGE) about radiation protection for endoscopic procedures, in particular endoscopic retrograde cholangiopancreatography (ERCP). Particular cases, including pregnant women and pediatric patients, are also discussed. This Guideline was developed by a group of endoscopists and medical physicists to ensure that all aspects of radiation protection are adequately dealt with. A two-page executive summary of evidence statements and recommendations is provided. The target readership for this Guideline mostly includes endoscopists, anesthesiologists, and endoscopy assistants who may be exposed to X-rays during endoscopic procedures.

Extremity exposure in nuclear medicine: preliminary results of a European study.

The Work Package 4 of the ORAMED project, a collaborative project (2008-11) supported by the European Commission within its seventh Framework Programme, is concerned with the optimisation of the extremity dosimetry of medical staff in nuclear medicine. To evaluate the extremity doses and dose distributions across the hands of medical staff working in nuclear medicine departments, an extensive measurement programme has been started in 32 nuclear medicine departments in Europe. This was done using a standard protocol recording all relevant information for radiation exposure, i.e. radiation protection devices and tools. This study shows the preliminary results obtained for this measurement campaign. For diagnostic purposes, the two most-used radionuclides were considered: (99m)Tc and (18)F. For therapeutic treatments, Zevalin(®) and DOTATOC (both labelled with (90)Y) were chosen. Large variations of doses were observed across the hands depending on different parameters. Furthermore, this study highlights the importance of the positioning of the extremity dosemeter for a correct estimate of the maximum skin doses.

Active personal dosemeters in interventional radiology: tests in laboratory conditions and in hospitals.

The work package 3 of the ORAMED project, Collaborative Project (2008-11) supported by the European Commission within its seventh Framework Programme, is focused on the optimisation of the use of active personal dosemeters (APDs) in interventional radiology and cardiology (IR/IC). Indeed, a lack of appropriate APD devices is identified for these specific fields. Few devices can detect low-energy X rays (20-100 keV), and none of them are specifically designed for working in pulsed radiation fields. The work presented in this paper consists in studying the behaviour of some selected APDs deemed suitable for application in IR/IC. For this purpose, measurements under laboratory conditions, both with continuous and pulsed X-ray beams, and tests in real conditions on site in different European hospitals were performed. This study highlights the limitations of APDs for this application and the need of improving the APD technology so as to fulfil all needs in the IR/IC field.

Extremity and eye lens doses in interventional radiology and cardiology procedures: first results of the ORAMED project.

The main objective of WP1 of the ORAMED (Optimization of RAdiation protection for MEDical staff) project is to obtain a set of standardised data on extremity and eye lens doses for staff in interventional radiology (IR) and cardiology (IC) and to optimise staff protection. A coordinated measurement program in different hospitals in Europe will help towards this direction. This study aims at analysing the first results of the measurement campaign performed in IR and IC procedures in 34 European hospitals. The highest doses were found for pacemakers, renal angioplasties and embolisations. Left finger and wrist seem to receive the highest extremity doses, while the highest eye lens doses are measured during embolisations. Finally, it was concluded that it is difficult to find a general correlation between kerma area product and extremity or eye lens doses.

Extremity ring dosimetry intercomparison in reference and workplace fields.

An intercomparison of ring dosemeters has been organised with the aim of assessing the technical capabilities of available extremity dosemeters and focusing on their performance at clinical workplaces with potentially high extremity doses. Twenty-four services from 16 countries participated in the intercomparison. The dosemeters were exposed to reference photon ((137)Cs) and beta ((147)Pm, (85)Kr and (90)Sr/(90)Y) fields together with fields representing realistic exposure situations in interventional radiology (direct and scattered radiation) and nuclear medicine ((99 m)Tc and (18)F). It has been found that most dosemeters provided satisfactory measurements of H(p)(0.07) for photon radiation, both in reference and realistic fields. However, only four dosemeters fulfilled the established requirements for all radiation qualities. The main difficulties were found for the measurement of low-energy beta radiation. Finally, the results also showed a general under-response of detectors to (18)F, which was attributed to the difficulties of the dosimetric systems to measure the positron contribution to the dose.

Evaluation of the calibration procedure of active personal dosemeters for interventional radiology.

An overview of the use of active personal dosemeters (APD) in interventional radiology is presented. It is based on the work done by the working package 7 of the CONRAD coordinated action supported by the EC within the frame of the 6th FP. This study was done in collaboration with the working package 4 of CONRAD to deal with the calculations required for studying the new calibration facility. The main requirements of the standard for the APD and the difficulties caused by the use of pulsed radiations are presented through the results of an intercomparison organised in a realistic calibration facility similar to the workplace situation in interventional radiology. The main characteristics of this facility are presented.

An overview of the use of extremity dosemeters in some European countries for medical applications.

Some medical applications are associated with high doses to the extremities of the staff exposed to ionising radiation. At workplaces in nuclear medicine, interventional radiology, interventional cardiology and brachytherapy, extremities can be the limiting organs as far as regulatory dose limits for workers are concerned. However, although the need for routine extremity monitoring is clear for these applications, no data about the status of routine extremity monitoring reported by different countries was collected and analysed so far, at least at a European level. In this article, data collected from seven European countries are presented. They are compared with extremity doses extracted from dedicated studies published in the literature which were reviewed in a previous publication. The analysis shows that dedicated studies lead to extremity doses significantly higher than the reported doses, suggesting that either the most exposed workers are not monitored, or the dosemeters are not routinely worn or not worn at appropriate positions.

An overview on extremity dosimetry in medical applications.

Some activities of EURADOS Working Group 9 (WG9) are presently funded by the European Commission (CONRAD project). The objective of WG9 is to promote and co-ordinate research activities for the assessment of occupational exposures to staff at workplaces in interventional radiology (IR) and nuclear medicine. For some of these applications, the skin of the fingers is the limiting organ for individual monitoring of external radiation. Therefore, sub-group 1 of WG9 deals with the use of extremity dosemeters in medical radiation fields. The wide variety of radiation field characteristics present in a medical environment together with the difficulties in measuring a local dose that is representative for the maximum skin dose, usually with one single detector, makes it difficult to perform accurate extremity dosimetry. Sub-group 1 worked out a thorough literature review on extremity dosimetry issues in diagnostic and therapeutic nuclear medicine and positron emission tomography, interventional radiology and interventional cardiology and brachytherapy. Some studies showed that the annual dose limits could be exceeded if the required protection measures are not taken, especially in nuclear medicine. The continuous progress in new applications and techniques requires an important effort in radiation protection and training.

Coincidence measurement of residues and light particles in the reaction 56Fe+p at 1 GeV per nucleon with the spallation reactions setup SPALADIN.

The spallation of 56Fe in collisions with hydrogen at 1A GeV has been studied in inverse kinematics with the large-aperture setup SPALADIN at GSI. Coincidences of residues with low-center-of-mass kinetic energy light particles and fragments have been measured allowing the decomposition of the total reaction cross section into the different possible deexcitation channels. Detailed information on the evolution of these deexcitation channels with excitation energy has also been obtained. The comparison of the data with predictions of several deexcitation models coupled to the INCL4 intranuclear cascade model shows that only GEMINI can reasonably account for the bulk of collected results, indicating that in a light system with no compression and little angular momentum, multifragmentation might not be necessary to explain the data.

IRSN methodological guide to conducting workplace studies in compliance with French regulations.

Under French regulations governing radiation protection of workers, dosimetric workplace studies are mandatory. However, their practical implementation is not described. IRSN has developed a guide to help stakeholders in the radiological protection of workers conduct such studies. It proposes a general methodology applicable to most cases and 'workplace sheets', which apply this methodology to specific occupational settings. At present, two sheets are available: conventional radiology and interventional radiology.

Workplace characterisation in case of rail transport of radioactive materials.

IRSN has been asked by SNCF (French Railways) to carry out measurements in order to establish the values of ambient dose equivalents H*(10) in the vicinity of shipments of radioactive materials to assess the external exposure to ionising radiation to which employees may be subjected during the carriage of radioactive goods. Detailed dosimetric characterisations of the wagons have been made and the external exposure at different stages of the work that is done by the employees have been measured in terms of H*(10). For the study presented in this paper, and corresponding to a used fuel shipment composed of UO2 and UO2-PuO2, it has been observed that the photon and neutron doses are very similar. In addition, the order of magnitude of the total dose integrated by an employee who would carry out 100 times the series of essential operational tasks, has been found to be approximately 250 microSv. This value is compared with those observed for other previously investigated shipments involving the exposure to photon fields only.

Impact of high-energy nuclear data on radioprotection in spallation sources.

The high-energy programme of the HINDAS European project has provided a large amount of experimental data and led to a better understanding of the spallation reaction mechanism and the development of more reliable spallation models. These data, or the new models, which have been implemented into high-energy transport codes, can be now used to predict with a larger confidence or, at least with a known uncertainty, some important quantities for the design of spallation sources. In this paper, examples concerning the residue production in a Pb-Bi target and the high-energy neutrons escaping the target are presented. In the first case, the activity and the amount of radioactive volatile elements that can be released, in case of a containment failure, are calculated and the level of confidence of the calculation is assessed. The second example shows that the models correctly predict the high-energy tail of the neutron spectrum, which is important for radioprotection in the facility.

Feasibility study of an active extremity dosimetry prototype.

In nuclear medicine departments, where radioactive sources are manipulated, the personnel can receive large radiation doses to the skin of their hands. For performing detailed characterisations and dose optimisations of these workplaces, active extremity dosemeters can be used as complementary tools to passive hand monitoring. Active extremity dosimetry is still a subject of research. In this context, IRSN has started a research and development programme. As a first step, a hospital workplace study has been performed using thermoluminescence dosemeters and has shown, in agreement with previous works, that the pads of the fingers, points that are very difficult to instrument, receive the largest doses. Numerical studies have now started, with the aim of calculating the dose equivalent gradients through the hands, in order to optimise the locations of the detectors.

Performance of a cylindrical tissue-equivalent proportional counter for use in neutron monitoring.

Tissue-equivalent proportional counters (TEPC) allow the measurements of the absorbed dose and the ambient dose equivalent for neutron fields. A device based on this approach, called NAUSICAA((1,2)), has already been developed by IRSN to be used in high energy neutron fields for space applications. The response of this detector underestimates significantly the dose equivalent at low energies (several hundred keV) which represent the major component of neutron fields at workplaces in the nuclear industry. A counter with a similar geometry (cylindrical detector) and a lower gas pressure was studied in order to simulate a 1 microm biological site. In 2003, the performance of the device was further improved by adding a small amount of 3He to the tissue-equivalent gas (propane based) in order to increase the response for the lower energies of neutrons. Three amplification circuits were used to cover lineal energy range from 10(-1) to 10(4) keV microm(-1). Tests were performed in monoenergetic neutron and source fields. This paper presents the experimental results obtained with this change.