Extremity Dosimetry

Information on eye lens dosimetry

Source: MAVIG GmbH /Radiation Protection Glasses

With the new German Radiation Protection Act (§78, sect 2, point 1) taking effect as of 31st of December 2018, the annual dose limit for eye lens is lowered from 150 mSv to 20 mSv.

The reduction is a consequence of recent data on the occurrence of radiation-induced cataracts in correlation with radiation exposure of the lens of the eye. As a result, especially in interventional radiology and cardiology, many work places are now being evaluated with regard to a possible eye lens risk exposure. It is likely that in many of these cases, monthly monitoring of the eye lens dose will become mandatory. This may also affect other work places in industry, research and medicine, including nuclear medicine or veterinary medicine.

Which jobs and activities are affected?

All previous national and international studies on this topic show that there is no clear correlation between the level of lens exposure and a certain activity.  Especially in radiology, the measured doses depend strongly on the individual experience of doctors and staff, the quality of the local radiation protection procedures, the used devices and structural radiation protection in their vicinity and on the use of personal radiation protection and safety equipment such as glasses or visors. The results of the studies on the affected workplaces and activities can be summarized with the foloowings:

Nuclear technology

Doses are not expected to reach or exceed the dose limit. Eye lens dose can be very well estimated with normal whole body dosemeters due to rather homogeneous radiation fields. Beta radiation is effectively shielded by the use of RP visors or RP glasses.

Nuclear medicine

In this field exposure to gamma rays (e.g. 99mTc), to high energy beta radiation (e.g. 90Sr/Y) and due to the presence of positron sources (e.g. 68Ga, 18F) is possible. Low energy beta radiation can effectively be removed by laboratory safety glasses and high energy beta radiation by means of radiation protection glasses. High energy gamma rays as well as 511 keV annihilation radiation from positron sources cannot be removed completely by RP glasses, however none of the studies indicates that extrapolated annual doses could reach the new annual limit.

Interventional Radiology and Cardiology

In all used interventional procedures the new dose limit can potentially be reached or even exceeded. Even though average and most likely doses are well below the limit, individual factors such as the lack of use of RP equipment such as local or personal shielding lead to maximum doses increased by up to a factor of 100. Most affected procedures are embolisations, PM/ICD, PTA/PTCA, TIPS, ERCP, RFA, etc. Consequently work place characterization or individual monitoring are required.

Surgery

There is no valid data available so far, but temporary measurements for risk assessment should also be carried out, especially in trauma surgery.

Veterinary medicine

There is not yet much data available in veterinary medicine, but initial studies show indications of similar problems as in human radiology.

Industry/Research

In this field no evidence for large eye lens doses has been found so far.

*Personal protective equipment (PPE)

The use of  PPE and especially RP glasses reduces the eye lens dose very efficiently. Lead glasses with 0.5 mm Pb equivalent shielding can be considered optimum, if the shielding extends beyond the glasses to cheekbones and temples.

When is it necessary to regularly monitor eye lens dose?

In accordance with the new Radiation Protection Ordinance, monitoring is mandatory if 15 mSv organ equivalent dose for the eye lens can be reached in a calendar year.

If personal protective equipment (PPE) is used correctly, e.g. radiation protection goggles or visors, the new annual limit should not be exceeded. 

To obtain an indication as to whether regular monitoring of the eye lens dose for your work place is required or not, there is a a survey measurement available (please see: "How to carry out survey measurements?").

How to carry out survey measurements?

In order to determine for which workplaces regular monitoring of the eye lens dose is required, we offer the possibility of survey measurements. These measurements can be carried out using special adaptors for eye lens dosemeters for wearing on a headband or for fixation to PPE. Since the start of 2019, these are available. Measurements are performed with Hp(3) dosemeters especially developed for the monitoring of eye lens dose in accordance with the new Radiation Protection Ordinance.

For setting up survey measurements please contact our customer service, Tel. +49 89 3187 - 2220, .

After determining your dosemeter requirements and the measurement period, you will receive an individual offer.

How can regular monitoring of the eye lens dose be provided in the future?

We will offer our new eye lens dosemeter as an official legal dosemeter as soon as the national certification by PTB Braunschweig is completed later in 2019. The new dosemeter can be integrated into radiation protection glasses developed by MAVIG. Alternatively, it can be worn with different adaptors, e.g. with an adhesive adaptor in other PPE or on a headband.

Information on the available types of glasses (type of prescription glasses, dosemeter location) and their lease or purchase price as well as on the adapter alternatives will follow as soon as glasses are PPE certified and become available later this year.

Final designs of the glasses:

Source: Marvig GmbH/ Radiation Protection Glasses

Source: AWST Munich

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