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20 July 2008

Answer to Question #6596 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment/Shielding — Equipment

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

I am a dentist in the military. When we are deployed (usually for 12- to 15-month periods) we use a portable HDX handheld x-ray device and digital x-ray sensor. My concern is for the safety of my technician who is holding the x-ray head. Most of the time, due to space and other conditions, I am also in the same room when the x ray is taken. The 6" tube has a scatter shield and the settings are 65 kV DC, 7 mA, and 0.15 seconds. We will take close to 20 x rays per day at this setting for the next 15 months. What amounts of scatter radiation exposure are we most likely getting? I am very concerned about any long-term effects. I have spoken to several other dentists who are/have been deployed and the same scenario exists. I would be grateful of any feedback.

I performed an Internet search for this device and was unable to find any information. I did, however, find a slide presentation on a handheld dental x-ray device called the Nomad by Aribex. In addition, I have performed physics testing on a Nomad at a federal hospital recently.

The concept of a handheld x-ray device immediately raises concern primarily because the operator has his/her hand wrapped around the unit, just under the x-ray tube, for all exposures. Based on an assumption that these units are Food and Drug Administration (FDA) approved in the United States, it is most likely that the radiation exposure to the operator is very low per x ray taken and still below acceptable limits for performing many procedures each day.

The vendor-supplied presentation that I found for the Nomad indicates that the use of a lower x-ray technique (due to use of digital image receptor), a shielded x-ray tube and cone assembly, and an external backscatter shield yields leakage radiation below FDA limits. The backscatter shield would reduce operator exposure due to scatter radiation produced in the patient, while the shielded x-ray assembly would protect against most of the leakage radiation from the x-ray tube itself.

Assuming the device you are using is FDA approved, it should be safe for one operator to use for normal work weeks. I recommend that the operator consider wearing an extremity dosimeter (ring badge) to monitor radiation dose. This will assure that the dose to the operating hand does not exceed any dose limits. I also recommend that you discuss this issue with the military health physicist who has jurisdiction over the use of your x-ray units, since it is likely that this individual may have training and/or vendor-supplied information regarding the radiation safety aspects of your unit.

Ken "Duke" Lovins, CHP

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