regional workshop on the international basic safety … documents...bss gsr part 3 • the icrp...

IAEA International Atomic Energy Agency

Regional Workshop on the

International Basic Safety Standards

Session 2: Implications of the New Dose Limit

for the Lens of the Eye

16-19 October 2012, Kiev, Ukraine

Igor Gusev

Radiation Protection Unit

Division of Radiation, Transport and Waste Safety

IAEA

ICRP statement on Tissue Reactions, April 2011

Lens of the eye

• Threshold now considered to be 0.5 Gy

• For occupational exposure, in planned exposure

situations, recommended:

• Equivalent dose limit of 20 mSv in a year

• Averaged over 5 year periods, with

• No single year exceeding 50 mSv

BSS Workshop Ukraine 2012

IAEA

BSS GSR Part 3

• The ICRP statement was issued while the new BSS was in

the final stages of approval

• Specific advice was sought from Member States

• ICRP statement was incorporated into the new BSS


IAEA

BSS dose limits for the lens of the eye – old & new

Planned exposure situations

Occupational Exposure of Workers Occupational Exposure of

Apprentices & Students Public Exposure

> 18 years 16 – 18 years

Equivalent dose to the lens of the eye:

New Old New Old New Old

20 mSv per year

averaged over 5

consecutive years, and

50 mSv in any single

year

150 mSv in a

year

20 mSv in a year

50 mSv in a year

15 mSv in a

year

15 mSv in a

year


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WHAT ARE THE IMPLICATIONS OF

THE NEW DOSE LIMIT FOR THE

LENS OF THE EYE?


IAEA

Image-guided interventional procedures

• Medical interventions performed using radiation to

“see what is going on”

• Initially in cardiology

• Now, utilized in many other specialties

• Rapid increase in use

• In some countries, a doubling rate every 3-4

years

• Interventionists often are not trained in radiation

protection

• In contact with the patient

• Occupational dose largely determined by

patient dose

• Often high patient doses


IAEA

Image-guided interventional procedures

The hardware • “Open” configuration

• Flexibility in orientation


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If no protective tools used for the eyes

• Significant amounts of

scatter will reach the

eyes of an operator

close to the patient

• For a typical workload

• Dose limit would be

exceeded

• Over time

• Opacities

X Ray tube

Dose rate to the eyes

5 μGy/min

e.g. Patient entrance surface

dose rate = 20 mGy/min

Per average IC intervention:

~ 100 – 400 µSv to the eyes

Average workload ~ 300 pat. /

year

Eye dose > 100 mSv per year


IAEA

What can be done?

A clear need for protective tools when performing image-

guided interventional procedures

Provide significant reduction in occupational

exposure to the eyes

But must be positioned correctly

Depending on design, up to 90% dose reduction for the dose to the eyes from scatter

Protective screens

Lead glasses


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If using protective tools

• Ceiling suspended screens and/or lead glasses

• ~ 10 µSv eye dose per procedure, or less

• For 300 procedures per year • ~ 3 mSv per year


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Other groups?

Industrial radiographers? • IAEA survey (ISEMIR project)

• 2% of radiographers in 2009

• Effective doses > 20 mSv

• Radiographer data & regulatory

body data, independently

• Eye doses?

• Not monitored

• Ratios of DT(eyes)/Ka to E/Ka at 400

keV

• ~ 1.2 (AP, ROT, ISO)

• Some industrial radiographers may

be at risk?

• What can be done?


IAEA

What are the implications of the new dose limit

for the lens of the eye?

• Who are the “at risk” occupational groups? • What can be done?

• Are eye doses being monitored?

• How good is the dosimetry?

• How will Regulatory Bodies implement the new

dose limit • How can compliance be assessed?


IAEA

IAEA Technical Meeting

2 - 4 October 2012

The New Dose Limit for the Lens of the Eye –

Implications and Implementation


IAEA

Thank you for your attention


[email protected]

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