Answer to Question #9730 Submitted to "Ask the Experts"

I am an interventional cardiologist. The way we interventional cardiologists work is that we stand parallel to the table with the patient and the x-ray tube is on the left side of us and we look straight perpendicular to the screens. This makes me think that the majority of the scatter radiation is coming from the left side/left front side of me. I use a wrap-around lead-equivalent apron that provides 0.5 mm protection on the sides, and in the front it overlaps to 1 mm. I wonder if it would be more meaningful to have more protection (thicker lead) on the left side of my body than just in the front only.

Would it be more meaningful to have a frontal apron of the same weight but with thicker lead than to have a full wrap of the same weight but less side/front protection? I almost always control the fluoro pedal—I do not remember exposing my back to the radiation.

A review of a recent paper (Zuguchi et al. 2008) indicates that the attenuation of the scattered x rays from interventional procedures for a 0.475 mm lead-equivalent apron ranges from practically 100% at 60 kV to about 96% for 120 kV. This would be consistent with the attenuation you are receiving from the nonoverlapped part of the lead apron you wear (i.e., to your left side, closest to the patient).

I'm not certain you could purchase a lead apron (or one of the composite lead aprons) that provides the equivalent of 1 mm of lead. Theoretically, you could wear two 0.5 mm lead-equivalent aprons and achieve that level of attenuation, but when you think about the added weight, it is very questionable as to the benefit in terms of additional attenuation provided.

In radiation protection, we constantly emphasize the importance of maintaining radiation exposures as low as reasonably achievable (ALARA). Sometimes, there is too much emphasis on "low" and not enough consideration given to what is "reasonable."  In your case, an additional 0.5 mm of lead equivalence would lower your exposure—I don't think anyone would argue with that. However, one must consider the added weight associated with a heavier or additional lead apron. How would that affect you personally and possibly your ability to perform the procedure (e.g., a fatigue factor)? In other words, is the benefit of the additional attenuation reasonable compared to the risk? 

Of course, the aforementioned information is provided without knowing the actual radiation exposure that you are receiving through your lead apron. That is pretty easy to determine. I assume you wear some type of dosimetry badge to monitor your exposure. Some institutions require the use of a single badge worn at the collar level, outside the lead apron. Other institutions require the use of one badge worn at the collar level, outside the lead apron, and another badge worn under the lead apron. If you have an under apron badge, I would suggest you wear it on the left side of your body, under the apron. That would give you the best information regarding how much radiation you are being exposed to under the apron. If you don't have an under apron badge, ask the individual who provides your badge (perhaps the radiation safety officer) for a badge to wear under your lead apron for a few weeks or months. I suspect you will find that the level of radiation penetrating your lead apron is a relatively small percentage of the maximum amount you can receive by regulation. While it is somewhat difficult to determine a numerical value for ALARA, regulators tend to feel that exposures that are less than 10% of the occupational limit typically are considered to meet the ALARA philosophy.

Finally, there are other shielding devices that can be used to reduce the scattered radiation from the patient. Ceiling-mounted lead-acrylic shields can be positioned between you and the patient. Lead drapes then are suspended from the x-ray table or image intensifier and are available. These types of devices can be used as additional protection to what is provided by the lead apron. There is most likely someone at your facility (usually a medical physicist or a health physicist) designated as the radiation safety officer. You should consult with that individual for additional recommendations.

Mack L. Richard, MS, CHP
Radiation Safety Officer

Reference
Zuguchi M, Chida K, Taura M, Inaba Y, Ebata A, Yamada S. Usefulness of non-lead aprons in radiation protection for physicians performing interventional procedures. Radiation Protection Dosimetry 131(4):531-534; 2008.