Can you handle the truth about personal radiation protection?
By Michael Crosby.
Healthcare professionals hear a lot of information and opinion about radiation protective apparel and the core materials they contain. It is high-time the record was set straight.
If I am exposed to very low levels of ionising radiation, I will not have any radiation-related health issues in the future.
While deterministic health effects appear in cases of exposure to high levels of radiation, stochastic effects are associated with long-term, low-level exposure. Increased levels of exposure make these effects more likely to occur, but do not influence the type or severity. Cancer and genetic mutation are the main health effects.
Lead, lead-composite and lead-free core materials are essentially the same in terms of weight and protection.
Lead core materials are made of dispersed lead mixed with matrix materials while lead-free products use no lead at all, instead replacing it with bismuth and lighter atomic weight elements such as tin, antimony and barium. Composite-lead uses the same light weight elements but add lead instead of bismuth.
As lead-free and lead-composite materials incorporate lower atomic weight elements, they can be made significantly lighter than lead products. Although protection levels are usually comparable to lead, lead-free and lead-composite materials have lower K-edge values meaning they can have reduced attenuation at certain kV levels.
Lead equivalences provides simple, informative indication of protection levels.
In attenuation terms, 0.25 Pb material provides 90% attenuation at 80kV or 98% with 0.50 Pb material (ASTM testing). Common conclusions are that using a 0.50 Pb apron provides twice the protection of a 0.25 Pb apron, or that the difference in terms of attenuation is only 8% (ASTM). Both are wrong.
ASTM attenuation figures suggest 0.50 Pb material does not provide close to twice the protection of 0.25 Pb material. Using transmission factors (TF) instead of attenuation percentages (TF 0.25 Pb = 10% 100%-90%); TF 0.50 Pb = 2% (100%-98%) the wearer of a 0.25 Pb apron will be exposed to approximately 5 times the radiation as someone wearing a 0.50 Pb apron (10% as compared to 2%).
As long as my protective apparel product is tested to a recognised certification standard, I can be sure that I am receiving good protection.
There are a number of issues with existing major certification standards such as IEC 61331-1:1994 and ASTM F2547-06. These range from the inability to properly test lead-free materials and being tested on main beam not scatter radiation, to overly aggressive beam filtrations and lack of real protection level data.
New standards such as IEC 61331-1:2013/2014 (Draft) and DIN 6857-1 specifically address lead-free and lead -composite products as well as some of the other issues identified above.
X-ray procedure technology has changes in recent times resulting in increased kV ranges.
Sometimes, with new technology comes new or increased risks. Certain X-ray technology has increased the kV range for procedures meaning there is greater risk of exposure. For example, C-Arm with Fluoroscope and X-ray machines operate at 50-80 kV and 80-100 kV ranges respectively while CT machines operate at a range of 100-140 kV.
As the protection of a apparel item increases, so does its weight.
Apart from differences between lead and lead-free or lead-composite materials, there is very little that can be done to lighten protective apparel without compromising protection. Beware of lighter aprons that offer less coverage area or use half the specified levels of protection in crossover panels – both present dangers of increasing exposure for wearers.
Certain inner core materials provide better protection than others.
Different core materials attenuate better or worse at differing kV levels. Additionally, certain materials will attenuate scatter radiation better than others. Ensure you are adequately protected by a core material by insisting that it complies to the IEC or an equivalent standard.