Search

The objective of this study was to evaluate the feasibility of assessing the eye lens dose when lead glasses are used, by attaching a small radiophotoluminescent (RPL) glass dosemeter to the lead glasses. RPL dosemeters were placed over and under the shielding of the glasses and their response was evaluated for a range of parameters, including irradiations in a standard X-ray beam and Monte Carlo simulations of a cardiac/radiologic intervention (scattered beam). For the specific situations taken into account in this study, the optimal position was found to be a dosemeter placed close to the bridge of the lead glasses, over its shielding.

The reduction in the occupational dose limit of the eye lens has created the need for optimising eye protection and dose assessment, in particular for interventional clinicians. Lead glasses are one of the protection tools for shielding the eyes, but assessing the eye lens dose when these are in place remains challenging. In this study, we evaluated the impact of the position of H p (3) dosemeters on the estimated eye lens dose when lead glasses are used in interventional settings. Using the Monte Carlo method (MCNPX), an interventional cardiology setup was simulated for two models of lead glasses, five beam projections and two patient access routes. H p (3) dosemeters were placed at several positions on the operator and the obtained dose was compared to the dose to the sensitive part of the eye lens (H lens). Furthermore, to reproduce an experimental setup, a reference dosemeter, H p (3)ref, was placed on the surface of the eye. The dose measured by H p (3)ref was, on average, only 60% of H lens. Dosemeters placed on the glasses, under their shielding, underestimated H lens for all parameters considered, by from 10% up to 90%. Conversely, dosemeters placed on the head or on the glasses, over their shielding, overestimated H lens, on average, up to 60%. The presence or lack of side shielding in lead glasses affected mostly dosemeters placed on the forehead, at the left side. Results suggest that both use of a correction factor of 0.5 to account for the presence of lead glasses in doses measured outside their shielding and placing an eye lens dosemeter immediately beneath the lenses of lead glasses may lead to the underestimation of the eye lens dose. Most suitable positions for eye lens dose assessment were on the skin, unshielded by the glasses or close to the eye, with no correction to the dose measured.

Assessing the radiation doses received by patients in computed tomography is still challenging. To overcome this, the American Association of Physicists in Medicine has introduced the concept of the size specific dose estimate (SSDE). However, the calculation of SSDE for head CT scans requires the knowledge of attenuation characteristics of the volume scanned, making its implementation in the daily clinical workflow cumbersome. In this study, we defined conversion coefficients from CTDIvol,16cm to SSDE for head CT scans based solely on the age of the patient. Using the head circumference-for-age from the child growth standards of the World Health Organization (WHO), the effective diameter-for-age was calculated for male and female individuals from 0 to 60 months-old. The effective diameter was converted into a water equivalent diameter-for-age, using a correlation established from the measurements of both quantities in 295 exams of male and female patients, from 0 to 18 years-old. WHO-estimated water equivalent diameter-for-age was validated against the measured water equivalent diameter-for-age. The head circumference-for-age from WHO was extrapolated for male and females individuals up to 18 years-old and their respective water equivalent diameter were estimated. Finally, the SSDE was calculated for all the CT head scans performed in a 9-years period in patients aged from 0 to 18 years old. Typical values of CTDIvol,16cm and DLP were also defined. SSDE varied from 0.80 up to 1.16 of the CTDIvol,16cm, depending on sex and age of the patient. WHO-estimated water equivalent diameter-for-age differed less than 20% from the measured water equivalent diameter-for-age. Typical values of SSDE varied from 28.5 up to 38.9 mGy, while typical values ranged from 30.9 up to 47.6 mGy for the CTDIvol,16cm and from 417.6 up to 861.1 mGy*cm for the DLP. SSDE can be directly calculated for head CT scans once the age of the patient is known.

Hospital based workers that perform interventional radiology are at risk of reaching the eye lens dose limit of 20 mSv/y. These workers are exposed to the radiation scattered by the patient, which creates a complex field, with low radiation energy reaching the eyes of the medical staff from wide angles. Therefore, the dosemeter used in the assessment of the eye lens dose of interventional radiologists needs to respond accurately in such conditions. In this study, the angular response of a commercially available radiophotoluminescent glass dosemeter, GD-352M, was optimized via Monte Carlo simulations, aiming at its use as eye lens dosemeter in interventional radiology. The improved dosemeter was manufactured and then characterized in terms of Hp(3), the quantity recommended for eye lens dosimetry. Its response was compared to the IEC 62387:2012 requirements for Hp(3) and to requirements proposed specifically for eye lens dosemeters used in interventional radiology. The improved dosemeter meets the IEC 62387:2012 requirements for energy and angular response for Hp(3) and also shows good agreement with the more strict requisites proposed for eye lens dosemeters to be used in interventional radiology.

Aims This study aimed to evaluate the effectiveness of ceiling suspended screens, lead glasses and lead caps in reducing radiation doses to the brains of interventional cardiologists. Methods and results Interventional procedures where the thorax of the patient is irradiated with different beam projections were modelled. The dose reduction in the white matter and hippocampus of the Zubal head phantom was studied for two sizes of ceiling suspended screens, two types of lead glasses and lead caps of surgical and hood models, which cover different regions of the head. Ceiling screens were the most effective, reducing the dose to brain tissue by 74% or even as much as 94%. The dose reduction provided by lead glasses varies between 10% and 17%. For the lead caps, it strongly depends on the model, varying from 6% (surgical) up to 68% (hood that also covered lower parts of the head). Conclusions The dose to the brain can be reduced by using appropriate radiation protection devices. This study has shown that lead caps are less protective than previously described and that the best protection is given by ceiling suspended screens, which are widely available in interventional theatres.

International audience; In the context of the decrease in the eye lens dose limit for occupational exposure to 20 mSv per year stated by the recent revision of the European Basic Safety Standards Directive 2013/59/EURATOM, the European Radiation Dosimetry Group (EURADOS) has organised in 2014, for the first time, an intercomparison exercise for eye lens dosemeters. The main objective was to assess the capabilities of the passive eye lens dosemeters currently in use in Europe for occupational monitoring in medical fields. A total of 20 European individual monitoring services from 15 different countries have participated. The dosemeters provided by the participants were all composed of thermoluminescent detectors, of various types and designs. The irradiations were carried out with several photon fields chosen to cover the energy and angle ranges encountered in medical workplace. Participants were asked to report the doses in terms of H-p(3) using their routine protocol. The results provided by each participant were compared with the reference delivered doses. All the results were anonymously analysed. Results are globally satisfactory since, among the 20 participants, 17 were able to provide 90 % of their response in accordance with the ISO 14146 standard requirements.

Recent studies demonstrated that lens opacities can occur at lower radiation doses than previously accepted. In view of these studies, the International Commission of Radiological Protection (ICRP), recommended in their Publication 118 to reduce the eye lens dose limit from 150mSv/y down to 20mSv/y. This implies the need of monitoring doses received by the eye lens. Small rod radiophotoluminescence (RPL) glass dosemeter GD-352M, which is currently common in personal dosimetry, could be suitable for this purpose. In this study, RPL dosemeters were characterized in terms of their energy (137Cs, 60Co and the X rays ISO narrow spectrum series) and angular dependence (0° up to 90°, with 2 energies: 137Cs and N60 X rays ISO narrow spectrum). All acquisitions were performed at the SCK•CEN – Belgium, on the cylindrical phantom. For selected energies and angles (137Cs, 60Co, N40, N60 and N80; 60° and 90°), the dosemeters were also irradiated on the ISO water slab phantom, at the Ruđer Bošković Institute - Croatia. All data were analyzed in terms of Hp(3). GD- 352M showed relatively good energy dependence at low energies, relative to 137Cs, on the cylindrical phantom. From 0° up to 45°, the dosemeters showed no significant angular dependence on the cylindrical phantom. However, at 90°, a difference of 68%, relative to 0°, was observed. Comparing these results with those obtained on the slab phantom, differences were mainly present at high angles. First results show that GD-352M has good properties related to Hp(3), although some improvements and further investigations are necessary.