New eye lens dosemeters for integration in radiation protection glasses

Simulation of Hp(0,07) beta and photon response of a BeOSL finger ring dosemeter

Simulation of a dosemeter's energy and angular response lowers development cost and time. To support development of a new beta sensitive dosemeter we simulate both the dosemeter and the skin dose in a rod phantom as there are no fluence to dose conversion coefficients in the ICRU Report 47 for electrons. Published spectra for BSS2, N-Series and S-Cs and S-Co were used to define sources, with CAD models used to define the simulation geometry. Simulation tools were validated with experimental beta and photon responses available for the BeOSL photon ring. The developed toolchain was then used to simulate several iterations of a beta sensitive detector element inside a beta ring holder, with the goal to minimise the need for repeated prototype fabrication and characterisation. Simulation results for the final design were compared to measurements on 3D printed prototypes with all radiation qualities, except 90Sr/90Y 0°, falling within measurement uncertainty.

Development of ring radiation dosemeters using 3D printing

Extremity radiation monitoring is an important tool for the assessment of occupational exposures to staff at a variety of workplaces where ionising radiation is used. This work shows the feasibility of applying 3D printing for the development of customisable ring dosemeters. The rings were developed using two types of resin, hard and flexible and has the possibility of sterilisation using different techniques. The printed ring dosemeter was associated with BeO optically stimulated dosemeters. The energy and angular response were found within ±20% in the energy range from 24 to 662 keV and from 0° to 60° angle of incidence. This contributes to the reduction of measurement uncertainty when compared with currently used thermoluminescent detectors dosemeters. The new ring dosemeter showed a satisfactory response with respect to the performance criteria of the IEC 62387 Standard, in addition to providing improved ergonomics in relation to the commercial ring dosemeter.

Protected and Unprotected Radiation Exposure to the Eye Lens During Endovascular Procedures in Hybrid Operating Rooms

OBJECTIVE

Radiation cataract has been observed at lower doses than previously thought, therefore the annual limit for equivalent dose to the eye lens has been reduced from 150 to 20 mSv. This study evaluated radiation exposure to the eye lens of operators working in a hybrid operating room before and after implementation of a dose reduction program.

METHODS

From April to October 2019, radiation exposure to the first operator was measured during all consecutive endovascular procedures performed in the hybrid operating room using BeOSL H_p(3) eye lens dosimeters placed both outside and behind the lead glasses (0.75 mm lead equivalent). Measured values were compared with data from a historic control group from the same hospital before implementation of the dose reduction program.

RESULTS

A total of 181 consecutive patients underwent an endovascular procedure in the hybrid operating room. The median unprotected eye lens dose (outside lead glasses) of the main operator was 0.049 mSv for endovascular aortic repair (EVAR) (n = 30), 0.042 mSv for thoracic endovascular aortic repair (TEVAR) (n = 23), 0.175 mSv for complex aortic fenestrated or branched endovascular procedures (F/BEVAR; n = 15), and 0.042 mSv for peripheral interventions (n = 80). Compared with the control period, EVAR had 75% lower, TEVAR 79% lower, and F/BEVAR 55% lower radiation exposure to the unprotected eye lens of the first operator. The lead glasses led to a median reduction in the exposure to the eye lens by a factor of 3.4.

CONCLUSION

The implementation of a dose reduction program led to a relevant reduction in radiation exposure to the head and eye lens of the first operator in endovascular procedures. With optimum radiation protection measures, including a ceiling mounted shield and lead glasses, more than 440 EVARs, 280 TEVARs, or 128 FEVARs could be performed per year before the dose limit for the eye lens of 20 mSv was reached.

Current status of eye-lens dosimetry in Canada

For occupational exposures in planned exposure situations International Commission on Radiological Protection (ICRP) publication 118 recommends an equivalent dose limit for the lens of the eye of 20 mSv yr^-1averaged over five years with no single year exceeding 50 mSv. This constitutes a reduction from the previous limit of 150 mSv yr^-1. The Canadian nuclear regulator, the Canadian Nuclear Safety Commission, responded to the ICRP recommendation by initiating amendments to theRadiation Protection Regulationsthrough a discussion paper which was published for comment by interested stakeholders in 2013. The revised equivalent dose limit of 50 mSv in a one-year dosimetry period for nuclear energy workers came into effect in January 2021. This paper presents the outcome of discussions with Canadian stakeholders in diverse fields of radiological work which focused on the implementation of the reduced occupational equivalent dose limit for the lens of the eye in their respective workplaces. These exchanges highlighted the existing practices for monitoring doses to the lens of the eye and identified current technological gaps. The exchanges also identified that, in many cases, the lens of the eye dose is anticipated to be well within the new dose limit despite some of the gaps in technology. The paper also presents the monitoring and eye-lens dose assessment solutions that are available based on different methods for eye-lens monitoring; presented together with criteria for their use.

Staff dose evaluation by application of radiation protection during endoscopic retrograde cholangiopancreatography (ERCP) procedures performed with a mobile C-arm

BACKGROUND

The radiation dose to staff performing endoscopic retrograde cholangiopancreatography (ERCP) is not negligible.

PURPOSE

To evaluate the shielding effect of a table-suspended lower-body radiation shield for the positions in the room occupied by the operator, assisting nurse, and anesthesiologist, used during ERCP procedures with a mobile C-arm.

MATERIAL AND METHODS

Eye lens dose, whole body dose, and extremity dose were measured with and without a table-suspended lower-body radiation shield in a phantom model and in clinical routine work. The effect of the shield was evaluated for each scenario and compared, and a projection was made for when shielding should be required from a regulatory point of view.

RESULTS

In the phantom measurements, the shield provided significant shielding effects on the body and lower extremities for the operator but no significant shielding of the eye lens. The shielding effect for the assisting nurse was limited to the lower extremity. The clinical measurements yielded the same general result as the phantom measurements, with the major difference that the shield provided no significant reduction in the whole-body dose to the operator.

CONCLUSION

The table-suspended shield has a significant shielding effect for the lower extremities of the operator and assisting nurse. For annual dose-area product values >300,000 cGycm², the protection of the operator should be reinforced with a ceiling-suspended shield to avoid doses to the eye lens and body in excess of regulatory dose restrictions.

Eye protection in interventional procedures

Data suggest that radiation-induced cataracts may form without a threshold and at low-radiation doses. Staff involved in interventional radiology and cardiology fluoroscopy-guided procedures have the potential to be exposed to radiation levels that may lead to eye lens injury and the occurrence of opacifications have been reported. Estimates of lens dose for various fluoroscopy procedures and predicted annual dosages have been provided in numerous publications. Available tools for eye lens radiation protection include accessory shields, drapes and glasses. While some tools are valuable, others provide limited protection to the eye. Reducing patient radiation dose will also reduce occupational exposure. Significant variability in reported dose measurements indicate dose levels are highly dependent on individual actions and exposure reduction is possible. Further follow-up studies of staff lens opacification are recommended along with eye lens dose measurements under current clinical practice conditions.

Report of IRPA task group on issues and actions taken in response to the change in eye lens dose limit

In 2018, the International Radiation Protection Association (IRPA) established its third task group (TG) on the implementation of the eye lens dose limit. To contribute to sharing experience and raising awareness within the radiation protection community about protection of workers in exposure of the lens of the eye, the TG conducted a questionnaire survey and analysed the responses. This paper provides an overview of the results of the questionnaire.

Evaluation of a 3D printed OSL eye lens dosimeter for photon dosimetry

This work demonstrates the use of high-resolution 3D printing to fine-tune the low energy dependence of an eye lens dosimeter holder associated to a BeO OSL detector element (ezClip). Five geometries of the denominated iBe dosimeter were developed, three with a variation in the thickness of the wall in front of the sensitive element that tailor the response at low radiation energies; and three with variations of width and curvature in order to vary the angular response of the dosimeter badges. Additive manufacturing was accomplished using stereolithography which gave a high degree of accuracy and precision. The optimised dosimeter badges showed a low energy and angular dependence, within -20% to +20% in the energy range of 24 keV to 662 keV and from 0 to 60° incidence; and within -10% to +10% in the energy range of 24 keV to 164 keV and from 0 to 60° incidence. In contrast to other dosimeters with higher effective atomic numbers, the use of BeO as the sensitive element resulted in a flat energy and angular dependence response at low energies. A significant reduction in the measurement uncertainty in the diagnostic radiology energy range was achieved.