Sink Your Teeth Into Radiation Safety by STEPHANIE PATRICK, BS, RT (R)(M)(QM)


Health and Senior Services—as of May 2023 there are close to 5,000 facilities in Missouri with ionizing radiation equipment, and 2,106 of those are dental sites.1


A All x-ray


units must undergo radiation safety testing, and the scheduling depends on what type of equipment a dental practitioner has installed in their office. This inspection must be performed by an approved Qualified Expert (QE), individuals the MRCP has recognized and approved as having a significant back- ground and training in radiation physics and safety, as well as proficiency in surveying devices producing ionizing radiation.


In this article, dental site requirements from the MRCP, general survey information and safe radiation practices will be discussed.


REGISTRATION DATES VS SURVEY DATES


All facilities that have operational ionizing radiation equipment must complete registra- tion documents from the state every two years and update any important information. The survey (inspection) timeline depends on the equipment.


All intraoral wall units, handheld/portable units and panoramic units are considered a class D and are required to be tested every six years prior to their due date; all cone-beam computed tomography units (CBCT 3D) are class E and are required to be inspected every three years due to the higher radiation output and dose. A practice that has both a CBCT unit and other dental x-ray units will have equipment on both survey schedules.2


The MRCP sends reminders for both the registration and survey dates to all practices generally 90 days before they are due, and the MDA works with the MRCP to provide an updated list of facilities and due dates at modental.org/radiationinspections.


ccording to the Missouri Radiation Control Program (MRCP)—an entity of the Missouri Department of


The MDA works with the MRCP to provide an updated list of facilities and due dates at modental.org/radiationinspections.


Noncompliance with either the registration renewal or the required radiation safety survey will result in a warning, followed by a cease-and-desist mandate.


When a dental practice moves locations or adds an x-ray unit to its site, there are ad- ditional stipulations from the MRCP. If the office relocates, even if it is just down the street, all equipment in the new location must be surveyed. In addition, when a unit is added to a practice, it must be inspected. If the unit is a handheld, panoramic or wall unit, it must be surveyed within 90 days of installation; if it is a CBCT unit, it must be inspected within 30 days. Should a dentist set up a new practice, all x-ray units must be surveyed for acceptance testing and regis- tered with the MRCP.2


QEs help dental sites


navigate the compliance process with adher- ence to radiation safety.


WHAT ARE WE REALLY INSPECTING AND LOOKING FOR DURING A SURVEY?


QEs are testing a variety of important aspects of the dental x-ray units that all boil down to important radiation safety basics: ensuring the dose to the patient is as safe and as low as possible; the output of the unit is operat- ing safely within set parameters; and, the operator of the equipment and surrounding staff will be safe from leakage and scattered radiation as well. In addition, we look at how the unit is set for making exposures to the patient and make recommendations if needed for patient safety.


General radiation physics aspects of the dental x-ray machine survey include testing the kVp, mA, timer, exposure rate, half value layer, reproducibility, linearity, and general mechanics of the dental x-ray unit itself (see Fig. 1). When panoramic and cone-beam CT units are surveyed, scattered radiation surveys will also be performed in the sur- rounding areas. CBCT units will generally produce at least 10 times as much scattered


18 focus | SUMMER 2023 | ISSUE 2


radiation compared to panoramic units.3 Some CBCT manufacturers involve addi- tional quality control testing protocols using phantoms, such as resolution capabilities, uniformity, collimation alignment and evalu- ation of materials, air and water.


For a quick physics refresher, kilovoltage (kV) is the energy and penetration power of the x-ray beam; milliamperage (mA) and time (in seconds) together represent mAs, which regulates the amount of x-ray photons being produced. If you double the mAs, you double the exposure rate and therefore the dose to the patient. When these values are out of limits, the unit must be serviced and recalibrated and sometimes replaced. After the testing is complete, the updated sum- mary results form is submitted to the MRCP by the QE.


Figure 1. Partial setup of an intraoral unit.


HOW MUCH RADIATION DOSE IS THE PATIENT REALLY RECEIVING?


The answer to that question depends on the type of equipment producing the radiation, technique used and receptor type. With most dentists using digital sensors instead of film, the dose to the patient is lower than in previous decades and can be reduced 40 to 70 percent with digital imaging.3


However, CONTINUED PAGE 20


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