Answer to Question #12406 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment and Shielding — Shielding

The following question was answered by an expert in the appropriate field:

Q

I am a medical assistant at a physician's office that utilizes a computerized tomography (CT) machine for imaging the sinuses. The room is small, but has lead shields in front of the machine and to the side of the machine. We wear radiation badges during the scan and they are sent in every few months. I was curious, we have never been told to wear vests and we are supposed to stay in the room while the scan is active. Often, the doctor also stays in the room. The machine was manufactured back in 2009, so it is a relatively new machine. How worried should I be of radiation exposure? There are some days I have done four scans, but most days I do none.

A

The use of x-ray equipment is regulated by the state that the equipment is located in. State regulations typically indicate a minimum amount of shielding for anyone who must stay in an x-ray room during a procedure. Ohio, for example requires persons in the room to be protected by at least 0.25 mm of lead equivalent material for scatter radiation and 0.5 mm of lead equivalent material for primary beam radiation. Typically, states will have the same or similar regulations (you should verify what the regulations are for your state). If these are the limits in your state, then the shields in the room would need to be at least 0.25 mm of lead equivalent and should be as tall or taller than you, and you must stand behind one during the exposure. If not, then you must wear a lead apron while in the room during the exposure.

Radiation dose limits for occupational radiation workers (you and anyone working in the room with you) are also state regulated. Typically, the radiation dose limits are 50 mSv y-1 for deep dose equivalent, 150 mSv y-1 for lens of eye dose and 500 mSv y-1 for shallow skin dose. As long as your dosimetry results for the year do not exceed any of these numbers, you are within state regulations. However, based on how you describe the situation you probably have results significantly lower than the above. Medical facilities use the As Low As Reasonably Achievable (ALARA) principle to keep radiation doses low. Typically, most radiation workers in medical facilities are below 30% of the annual dose limits, and most of those persons are below 10% of the annual dose limits. If your results on an annual basis are below 30% of the limits above, and you are following the protection practices of time, distance, and shielding, then you do not need to be worried about radiation exposure.

Kennith "Duke" Lovins, CHP

Reference
Ohio Administrative Code OAC 3701:1-66-02(G)(3)(a) & (b). Available at https://codes.ohio.gov/ohio-administrative-code/rule-3701:1-66-02. Accessed 18 June 2018.

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 18 June 2018. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.