Posted:
3/5/2019
Dr. Juan Yepes
Recently, there has been increased concern in the public and with healthcare professionals about exposure to radiation (medical and dental) in children. In 2007, the International Commission on Radiation Protection changed the calculation of the effective dose from ionizing radiation and this change moved back the interest in the concept of As Low As Reasonably Achievable.
In comparison with adults, children are inherently at greater risk of cancer induction from radiation exposure. Sensitivity to radiation is higher early in life. The greater sensitivity in children is probably related to a rapid cell division in developing tissues. The radiation exposure from a single dental diagnostic procedure is usually small. Because of the increased lifetime risk per unit dose for children, the potentially higher doses, and the increasing frequency of pediatric radiology procedures, including dental that use radiation can lead to a small, but non-negligible, increase in the risk of cancer. While these procedures are clearly beneficial, the magnitude of exposure of children can often be reduced without significant loss of information.
The Alliance of Radiation Safety in Pediatric Imaging, is a coalition of different and numerous healthcare organizations dedicated to provide safe, high quality pediatric imaging. [1] The main mission of the Alliance is to create and increase awareness in the imaging community of the need to adjust radiation dose when imaging children. The American Academy of Oral and Maxillofacial Radiology, the American Academy of Oral and Maxillofacial Pathology, The American Academy of Pediatric Dentistry, The American Dental Association, the American Association of Oral and Maxillofacial Surgeons, The American Association of Endodontists, and The American Association of Orthodontists are part of the alliance. The Image Gently in dentistry focuses on improving safety and effectiveness in pediatric imaging of the maxillofacial complex by informing dental professionals and parents about radiation safety best practices.
The campaign outlines six steps during pediatric dental procedures:
- Select x-rays for individual needs, not merely as a routine
- Use the fastest image receptor possible
- Collimate the beam to areas of interest
- Always use thyroid collars
- Child-size exposure time
- Use cone-beam CT only when necessary
Reducing exposure in dental imaging with children: Justification and Rectangular Collimation
· Justification
Justification refers to the pertinence of each radiograph performed. There are no limits in the exposure when there is a clear justification. The clinician has the responsibility to assure that each exposure is justified. If the image is indicated, there are no limits or restrictions on patient exposure. [2] In the pediatric patient, as well as with adults, radiology is part of the diagnostic process but it is not the only piece of the diagnostic diagram. The decision is made on the findings from the patient history, clinical examination, and review of any previous radiograph. Critical is also the particular circumstances of each patient. For example, a bitewing radiograph is probably not justified in a child with posterior open contacts. The critical point is that the dentist must take the decision placing into the account the individual characteristics of the patient. The anticipated individual benefits must be that the radiographic examination is likely to add new information to the patient’s treatment. The American Academy of Pediatric Dentistry endorsed the selection criteria guidelines published by the American Dental Association. [3]
· Rectangular Collimation
Several ways are available to limit the size of the x-ray beam. The National Council on Radiation Protection and Measurements (NCRP) Report 145 (2003) [4] provides radiation protection guidance for the use of x-rays in dental practice. The NCRP was charted by the U.S. Congress in 1964 to perform several tasks related to the use of radiation, including to periodically assess new technologies and radiation safety practices in order to make recommendations. Following the report, dentists and patients can obtain maximum benefit and minimum radiation exposure to patient, operator and the public. Rectangular collimation has been widely available for several decades. Several US dental schools (probably the majority) recommend the use of rectangular collimation. However, there is not a significant acceptance in the dental office.
Using the appropriate collimation to the precise size of the image receptor eliminates scatter radiation. When scatter radiation hits the receptor, the result will be a reduction in image quality. Most companies produce large, round cones with large x-ray beam patterns so the operator will be sure to expose the film or receptor. Round collimation adds scattered radiation, decreases the image quality, and increases the patient radiation dose. The NCRP Report 145 suggests that rectangular collimation of the beam shall be used routinely for periapical radiography [5]. Each dimension of the beam, measured in the plane of the image receptor, should not exceed the dimension of the image receptor by more than 2% of the source-to-image receptor distance. Advantages of rectangular collimation include the reduction of scatter radiation and the increase of the image contrast. Scattered radiation adds unwanted and non-diagnostic photons to the image and that decreases the contrast.
Juan F Yepes DDS, MD, MPH, MS, DrPH is an Associate Professor of Pediatric Dentistry at Indiana University School of Dentistry and Riley Hospital for Children. He is an active member in the American Academy of Pediatric Dentistry, the American Academy of Oral and Maxillofacial Radiology, the American Dental Association and Indiana Dental Association. Hear him speak at the 2019 Hinman Dental Meeting and learn more about his courses here.
