Answer to Question #12614 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment/Shielding — Shielding

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

Q

Logic dictates that the new handheld x-ray machines at a dentist office is more dangerous to the patient. Handheld x-ray machine manufacturers claim they protect the dental worker from backscatter radiation with a cone. Logic would dictate it thereby bounces off the cone right back at the patient's face including their sensitive eyes. Dentists are increasingly using them, so my question is: Do these devices cause more backscatter radiation on the patient and shouldn't this be disclosed to the dentist and their patients by the manufacturers?  

A

Several studies have been published that show patient doses for handheld dental x-ray units is the same as, or lower than, doses from conventional dental x-ray systems. 

There are several reasons for this. First, the position indicating device (PID) on the Aribex Nomad system (the most commonly used system) is a smaller diameter irradiating a smaller tissue volume, 6 cm vs 7 cm, resulting in a 25% reduction in radiation dose to the patient. Second, the x-ray waveform has little fluctuation resulting in a "harder" x-ray beam which penetrates the tissue more easily, thereby requiring less dose. And, the leaded acrylic shield around the PID is almost in contact with the patient and absorbs most of the radiation falling on it, i.e., there is minimal backscatter from this lead shield.

Joel Gray, PhD, FAAPM

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 17 October 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.