Answer to Question #7133 Submitted to "Ask the Experts"

I am a nurse working in a nuclear stress laboratory and am now in my first trimester of pregnancy. My office does not have lead aprons. I am wondering if I am at risk by being near patients injected with ²⁰¹Tl or ^99mTc sestamibi. Should I insist on an apron?

The radiation dose received by nursing personnel working in a nuclear stress laboratory is generally low and not a concern even if the individual is pregnant. However, it is also important to keep radiation dose ALARA (as low as reasonably achievable). In a nuclear stress laboratory, this means appropriately applying the radiation safety principles of time, distance, shielding, and contamination control.

You specifically asked about applying shielding by wearing a lead apron. The thickness of the lead makes a difference in the amount of shielding provided. You indicated use of thallium (²⁰¹Tl) or sestamibi (^99mTc). For ²⁰¹Tl and ^99mTc, a lead apron of 0.5 mm (equivalent*) lead could reduce the radiation dose up to 75%, and a 0.25 mm (equivalent*) lead apron would reduce the level by about 50%. Prior to determining if wearing an apron is appropriate, all the principles of ALARA need to be applied. Lead aprons are heavy and significantly affect a person's mobility. Frequent wearing of lead aprons may result in back issues.

In a nuclear stress laboratory, radiation doses to nursing personnel can favorably be reduced by applying the radiation safety principles of time, distance, and contamination control. Minimize your time in any area where radiopharmaceutical dosages and/or patients who have recently been administered a radiopharmaceutical are present. Maximize distance whenever possible. Maximizing distance is one of the best and often easiest radiation safety principles to apply as a nurse in a nuclear stress laboratory. If you do not have to be in direct contact with a patient to perform your duties, step back a step or two. Moving from a couple of feet away to four feet away reduces your radiation exposure by about a factor of four (400%). Perform good contamination control by practicing universal precautions, washing your hands, and monitoring yourself regularly.

Finally, although the radiation dose generally received by nursing personnel working in a nuclear stress laboratory is generally low and not a concern even if the individual is pregnant, confidence and peace of mind are also important. I recommend that you discuss your concerns and specific applications of radiation safety principles with your radiation safety officer. The radiation safety officer is responsible by regulation to ensure the radiation dose to you and your fetus is maintained within regulatory limits and is kept ALARA and to provide you guidance in regard to radiation safety. If desired, declare your pregnancy and request a fetal dosimeter. Although the doses detected by most dosimeters are not available for a period of time, they do document the dose received and frequently confirm that the dose received is either indistinguishable from natural background or very low and that applying radiation safety principles minimized any radiation dose received.

Victoria Morris, MS, CHP

*The term equivalent is used here because the actual shielding material may not be lead but has the shielding characteristics that make it equivalent to either 0.5 mm or 0.25 mm of actual lead.