educational, and research activities. Occupational exposure is employee-related radiation exposure that occurs in a variety of work situations, such as medical (includes dental and veterinary medicine), aviation, nuclear power, military, academic, and industrial environments. Among occupationally exposed individuals, the medical and aviation categories comprise the greatest number of workers and the highest collective effective dose. Individuals in the aviation industry experience a higher concentration of natural radiation at higher altitudes due to a higher amount of radiation from cosmic rays present at higher altitudes than the level of cosmic radiation at ground level (Alden, 2020). However, industrial and occupational sources combined account for less than 0.01% of the total annual effective dose per person. Table 3: Diagnostic Examinations with Typical Effective Dose Type Examination Effective Dose (mSv) Effective Dose (mrem)
FM = full mouth; PSP = photostimulable phosphor; CBCT = cone beam computed tomography. Note . Adapted from American Dental Association. (2016). Oral health topics: X-rays. Retrieved from http://www.ada.org/en/member- center/oral-health-topics/x-rays; (American Dental Association, 2019; Health Physics Society, 2021; Effective doses in radiology and diagnostic nuclear medicine: A catalog. Radiology, 248 (1), 254-263; and Radiological Society of North American. (2016). Radiation dose in X-ray and CT exams: Effective radiation doses in adults . Retrieved from http://www.radiologyinfo.org/en/info.cfm?pg=safety-xray#safety- benefits-risks. Table 4 summarizes radiation sources and exposure doses, revealing that the radiation from natural and artificial sources results in an average effective dose of 6.2 mSv per year for persons living in the United States (United States Environmental Protection Agency, 2021b). Table 4: Source Contribution to Annual Effective Dose
Effective Dose (mrem)
Radiation Source Radon (internal inhalation)
Percent Contribution
Effective Dose
Chest radiography
0.1
10
Type
Medicine (exposure from single diagnostic x-ray)
Mammography
0.4
40
37
2.28
228
Upper GI series
6.0
600
Coronary CT angiography
12
1,200
Cosmic (space)
5
0.33
33
Natural 3.1 mSv
Kidney (filtration rate) 99mTc DTPA Thyroid scan (sodium iodide-123) Bone scan 99mTc MDP
6.0
600
Internal terrestrial External terrestrial
5
0.29
29
1.9
190
Nuclear medicine (exposure from entire procedure)
3
0.21
21
6.3
630
Computed tomography
24
1.47
147
Brain (PET) 18F FDG 14.1
1,410
Nuclear medicine
12
0.77
77
Heart stress-rest test 201Tl chloride
41
4,100
Medical 3.0 mSv
Interventional fluoroscopy Conventional radiography/ fluoroscopy (dental 2.5%)
7
0.43
43
Four bitewings PSP or F-speed film rectangular collimation
0.005
0.5
5
0.33
33
Panoramic
0.01
1
FM survey PSP or F-speed film
0.035
3.5
Consumer
2
0.13
13
Other 0.1 mSv
rectangular collimation
Occupational
<0.1
0.005
0.5
Dental
Industrial
<0.1
0.003
0.3
FM survey PSP or F-speed film round collimation Dentoalveolar CBCT small and medium field view Maxillofacial CBCT large field view
0.171
17.1
Total 620 Note : Adapted from Health Physics Society, 2020; United States Nuclear Regulatory Commission, 2020. All sources 100 6.2
0.011 to 0.674
1.1 to 67.4
0.030 to 1.073
3 to 107.3
RADIATION SAFETY AND PROTECTION
Radiation safety and protection are based on the ALARA principle. ALARA is an acronym for “as low as reasonably achievable.” This principle maintains that exposures to ionizing radiation should be kept as low as possible (American Dental Association, 2019). It means that every effort should be made to reduce unnecessary radiation exposure for patients and dental professionals alike.
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