Radiation Safety CONTINUED FROM PAGE 18


the digital world allows for a wider exposure latitude regarding radiation output, meaning the operator can use a variety of technical factors and still have an acceptable image. The set factors chosen might produce more or less radiation than necessary, as the sensor and digital processing will adjust to pro- duce an image. This is not the case with the old-style film imaging, when doubling the output resulted in an image that was twice as dark. It is important the radiation output be routinely surveyed by the QE to ensure the technical factors are within acceptable limits.


xdr alara collimator


We are all exposed to background radia- tion, including cosmic radiation, every day. Professional radiology organizations, such as the Radiological Society of North America and the American College of Radiology, compare the medical dose to patients to being exposed to background radiation for a better understanding of exposure dose. For example, a series of intraoral x-rays taken on a patient is equivalent to about one day of background radiation; a panoramic x-ray is equivalent to about three days of back- ground radiation; and, a cone-beam CT scan is equivalent to about 22 days of background radiation.4


shield must remain in place during exposure to protect the operator3,5


(see Fig. 3).


The NCRP states the operator of a handheld x-ray unit is not required to wear a protective lead apron although the state of Missouri recommends one be worn.3,5


It is also advised


the facility provide personal dosimeters to operators of these devices for the first year of use to determine whether ongoing monitor- ing is needed. Personal dosimeters should be worn for occupational workers who are likely to receive an annual effective dose of 100 mrem or higher (1 mSv).3,6


Many of the CBCT units have parameter selections that include normal and also higher definition outputs, which can significantly increase the patient’s dose. Comparatively, a chest x-ray dose is about 10 days of background radiation, and a chest CT scan is about two years’ worth.4


backwards compatible ring with existing rinn-type aiming rings


There are risks associated with all x-ray imaging, and the benefit to the patient must outweigh the risk. Ionizing radiation can cause damage to DNA and increases a chance of developing cancer.3


ARE HANDHELD X-RAY UNITS SAFE?


There are currently seven manufacturers approved by the MRCP for handheld dental x-ray devices.5


Figure 2. External rectangular collimators for intraoral units. Image courtesy of XDR Radiology.


In addition, the National Council on Radia- tion Protection and Measurements (NCRP) recommends utilizing rectangular collima- tion for intraoral radiographs, which is usually an attachment to the round cone end of the unit (see Fig. 2). This practice improves image quality and reduces patient dose by four to five times; the beam size will more closely match the image receptor shape. The operator does need to be more precise in the exposure alignment preparation so anatomy cutoff will not occur on the image, and it is noted that this technique is not currently in use in most offices.3


For those sites still using


film, higher speed film, such as E or F speed, must be utilized to decrease patient dose while still maintaining image quality.3


Figure 3. Example of an approved handheld dental x-ray unit.


20 focus | SUMMER 2023 | ISSUE 2 These x-ray units are increas-


ing in popularity due to their ease of use by being lightweight and portable in multiple operatories within a practice. The output is similar to an intraoral wall unit, with addi- tional built-in housing shielding for operator safety, and the attached leaded acrylic scatter


There are several organizations that have current campaigns to lower patient dose and improve radiation safety. Image Gently is an alliance that advocates lowering the exposure factors and using a smaller field of view for pediatric imaging.7


Image Wisely


aims to educate imaging professionals on using appropriate techniques and radiation dose monitoring for safety in adult imaging.8 In summary, there are multiple methods for dental practices to utilize to keep patients and staff safe while performing radiographic imaging.


Intraoral, panoramic and cone-beam CT imaging all have an excellent purpose for spe- cific anatomical diagnosis and procedures. With proper technique, shielding and routine testing being employed, QEs assist sites with radiation safety equipment surveys to ensure these units continue to be operated with adherence to standardized limits and keeping dose as low as is reasonably achievable for the safety of all patients and dental staff.


WHAT ABOUT SHIELDING THE PATIENT?


According to the NCRP’s Report No. 177, “Technological and procedural improve- ments have eliminated the requirement for the radiation protective apron; however, some patients expect it and may request it. Thyroid shielding is required for patients due to the high radiosensitivity of the thyroid when it will not interfere with the exam.” A significant portion of the dose to the body is from internal scattered radiation which can- not be shielded.3 statements.


The MRCP supports these


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