Answer to Question #13454 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
I am a dental hygienist. I have been instructed to start using a handheld dental x-ray machine. How does the amount of radiation from a handheld/portable dental x-ray machine compare to that from a wall-mounted dental x-ray machine?
The bottom line: It is possible that in some situations operator exposure could be greater from handheld dental x-ray units than from wall-mounted dental x-ray units. If operated and maintained properly, however, handheld units should still keep operator exposure well below regulatory limits on occupational exposure.
A traditional (i.e., wall-mounted) dental x-ray machine is connected to a flexible mechanical arm which is mounted on the wall of the treatment room. The wall-mounted unit generates the x-ray beam after the operator has stepped behind a wall or other appropriate barrier, and thus the operator should be protected from essentially all x rays in the beam itself (i.e., the "primary beam"), and x rays that would be leaked from the machine ("leakage") and emitted from the patient ("scatter").
Due to the cost and bulk of wall-mounted x-ray machines, they are typically not available in every treatment room of every dental office, and therefore the patient must sometimes be moved from one room to another in order to make use of the wall-mounted machine. Handheld dental x-ray units are considered more convenient in some clinical situations, as they can be brought to the patient. These handheld units are comparable in size to a small handheld kitchen mixer or handheld carpenter's drill.
A handheld dental x-ray unit is held at arm's length by the operator and the operator sits next to the patient while the x-ray beam is generated. Handheld units are designed to protect the operator from the primary beam, from leakage radiation, and from scattered radiation. Research performed on such units has demonstrated that, if operated according to manufacturer's instructions, radiation exposure to the operator is well below that which would exceed regulatory limits on occupational exposure for dental personnel. However, given the proximity of the operator to the handheld unit, the exposure of the operator of a properly operated handheld unit is likely to be slightly higher than the exposure to the operator of a properly operated wall-mounted unit. In both cases, with proper operation of a properly maintained unit, the operator's exposure should be well below the regulatory limit on occupational exposure.
Because the operator is in control of the distance of the unit from the operator's body, and because the operator controls the angle at which the handheld unit is positioned, the amount of x-ray exposure of the operator's body could vary from one situation to the next.
To repeat the bottom line: It is possible that in some situations operator exposure could be greater from handheld units than from wall-mounted units. This bottom line is supported by a recent paper comparing five different handheld dental x-ray units.
If you are required to use a handheld dental x-ray unit, you could ask your employer to provide dosimetry monitoring for a few months in order to confirm that your occupational exposure is well below the regulatory limit.
S. Thomas Deahl, DMD, PhD
Editor’s note: Handheld dental x-ray machines are relatively new. The HPS has received other questions regarding these units.You may also want to review those questions and answers.Some specifics about the question topic have been addedto the title in parentheses.
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