radiation_safety_in_dental_practice.pdf

Radiation Safety In Dental Practice A study guide and excerpts from The California Radiation Control Regulations pertaining to dental practice Radiation Safety Protection Program template Copyright © 2014 California Dental Association. California Dental Association 1201 K Street, Sacramento, CA 9...

Radiation Safety In Dental Practice A study guide and excerpts from The California Radiation Control Regulations pertaining to dental practice Radiation Safety Protection Program template Copyright © 2014 California Dental Association. California Dental Association 1201 K Street, Sacramento, CA 95814 888.232.7645 | cda.org Radiation Safety In Dental Practice | A Study Guide Table of Contents Acknowledgements................................................................................................................................... 2 Introduction.............................................................................................................................................. 3 Section I – Licensed Dentist and X-ray Machine Registrant Responsibilities........................................................ 4 A. General Responsibilities................................................................................................................ 4 B. Specific Responsibilities................................................................................................................ 4 C. Enforcement of Regulatory Prohibitions........................................................................................... 5 D. Compliance with Posting and Recordkeeping Requirements............................................................... 5 E. Dental Personnel Training and Competency Evaluation..................................................................... 5 F. Compliance with Occupational Exposure Requirements.................................................................... 6 Section II – Dental Radiographic Machine Requirements................................................................................ 7 A. X-ray Tube Housing...................................................................................................................... 7 B. Collimating Device – Restricting the Size of the X-ray Beam............................................................... 7 C. X-ray Beam Filtration.................................................................................................................... 7 D. Exposure Cord............................................................................................................................ 8 E. Exposure Timer............................................................................................................................ 8 F. X-ray Tube Head and Flexible Arm Assembly................................................................................... 8 G. Portable X-ray Units...................................................................................................................... 8 H. Cone Beam Computed Tomography (CBCT) Units............................................................................ 8 Section III – Patient Protection..................................................................................................................... 9 Section IV – Responsibilities of Dental Personnel Operating X-ray Equipment.................................................. 10 A. Protect Patient from Unnecessary Radiation Exposure..................................................................... 10 B. Use Fast Image Receptors........................................................................................................... 10 C. Plan Dental Radiographic Procedures Carefully and Avoid Unnecessary Retakes............................... 10 D. Using Proper Kilovoltage (kV) ..................................................................................................... 11 E. Milliamperage (mA) and Time Setting........................................................................................... 11 F. Protecting the Operator from Unnecessary Radiation Exposure........................................................ 11 Section V – Dental Radiographic Quality Assurance (QA) and Quality Control (QC)....................................... 13 Section VI – Equipment QA Requirements (General Provisions)..................................................................... 15 PRCD120-1214 Radiation Safety In Dental Practice – A Study Guide | 2 of 69 cda.org/practicesupport Table of Contents, con’t. Section VII – Guidelines for Prescribing Dental Radiographs......................................................................... 16 Section VIII – Occupationally Exposed Women of Childbearing Age............................................................. 20 Section IX – Dental Radiation Protection – Protective Barriers........................................................................ 22 Section X – Glossary of Terms Pertaining to Dental Radiography................................................................... 23 APPENDIX I – Excerpts from the California Radiation Control Regulations Pertaining to Dentistry....................... 29 APPENDIX II – The Dental Monitor Display and Image Quality Considerations................................................ 50 APPENDIX III – Film Processing................................................................................................................. 57 APPENDIX IV – Radiation Safety Program Template..................................................................................... 63 Acknowledgements The California Dental Association thanks the following individuals for their assistance and contributions to this guide. Kenneth Abramovitch DDS, MS Loma Linda University School of Dentistry Linda Angin, DDS University of California, San Francisco School of Dentistry Elham Radan, DDS, MSc Herman Ostrow School of Dentistry of USC Dwight Rice, DDS Loma Linda University School of Dentistry Lisa Russell California Department of Public Health Radiological Health Branch Any comments or inquiries about this guide should be directed to CDA Practice Support at [email protected], or 916.443.0505, or 800.232.7645. Radiation Safety In Dental Practice – A Study Guide | 3 of 69 cda.org/practicesupport Introduction Licensed dentists play an important role in maintaining radiation exposures of patients and staff as low as reasonably achievable (ALARA). Greater numbers of intra-oral radiographs are being requested and a wide range of other dental radiographic examinations (panoramic, cephalometric) are being performed on a routine basis with the addition of advanced imaging modalities (CBCT). Individuals who operate dental X-ray equipment must have a basic knowledge of the inherent health risks associated with radiation and must have demonstrated familiarity with basic rules of radiation safety as explained in this study guide. Licensed dentists should follow the FDA/ADA Guidelines for Prescribing Dental Radiographs. Digital imaging with photostimulable phosphor plates or solid state image receptors (i.e., CCD or CMOS receptors) forego the need for darkroom processing of film. However, quality assurance on maintenance of the receptors, phosphor plate scanners, computers and monitors take on more importance in the management of images acquired with x-radiation. Faulty management of digital data could possibly necessitate remake exposures thus violating the ALARA principle. Can patient exposure be reduced without reducing diagnostic quality? The answer is yes. This was proven by dentists who participated in the Dental Exposure Normalization Technique (DENT) program, developed by the Food and Drug Administration’s Center for Devices and Radiological Health and State radiological health programs. The American Dental Association endorsed the DENT program to aid dental facilities in identifying and correcting exposure problems. What are appropriate exposure levels for dental radiographs? The answer must come from dentists who must evaluate exposure levels used in their facilities and compare these exposure levels to values “generally accepted” as providing diagnostic quality images without overexposure to patients. Generally accepted values are provided in a table in Appendix I. Radiation Safety In Dental Practice – A Study Guide | 4 of 69 cda.org/practicesupport Section I – Licensed Dentist and X-ray Machine Registrant Responsibilities A. General Responsibilities Each licensed dentist and X-ray machine registrant must take all precautions necessary to provide reasonably adequate protection to the life, health, and safety of all individuals subject to exposure to radiation. This includes judicious prescription of radiographs for individual patients based on selection criteria noted in Section VII. B. Specific Responsibilities 1. Registration of Dental Radiographic Equipment Dental X-ray machines and facilities with X-ray machines must be registered with the State Department of Public Health, Radiologic Health Branch in Sacramento within 30 days of acquisition. The owner of a new dental facility must submit the Radiation Machine Registration for New Registrants form RH 2261N. Already registered facilities should use form RH 2261C. The vendor reports machine installation to the FDA and to the State but cannot register the machine on behalf of the owner. Change of name, address, location, sale/transfer/disassembly of equipment or purchase of additional equipment must be reported to the Radiological Health Branch in Sacramento within 30 days of such change using form RH 2261C. Machine registration must be renewed every two years upon payment of the specified fee. 2. Radiation Protection – General Requirements The licensed dentist and X-ray machine registrant must: a. Take all precautions necessary to provide reasonably adequate protection to the health and safety of individuals who are subject to radiation exposure. The main purpose in the control of radiation exposure is to ensure that all exposures are justified in relation to their benefits; that necessary exposures are kept as low as reasonably achievable (ALARA); and that the doses received by patients and personnel are kept well below the allowable limits. b. Provide radiation safety rules to dental personnel including any restrictions of the operating technique required for the safe use of the particular dental X-ray equipment. c. Ascertain that dental personnel demonstrate competence in using the X-ray equipment and imaging software, and comply with the radiation safety rules. d. Assure that individuals whose job requires use of X-rays should be provided individual or personnel monitoring devices. Monitoring devices must be provided if the anticipated annual dose exceeds 10% of the annual occupational dose limits (10CFR20 section 20.1201(a)). Documentation of the basis for not monitoring must be provided upon inspection. Monitoring is strongly recommended for declared pregnant employees as fetal exposure limits are considerably lower. An employee (not declared pregnant) may wear a monitoring device for one year, or for one three-month period with the results extrapolated to determine an annual exposure. If the annual exposure is less than 10% of the maximum allowable dose (5 rems), then monitors need not be worn. This procedure would need to be repeated periodically and whenever changes are made that might affect radiation safety or output to insure personnel safety. An alternative to monitoring is to hire a professional health physicist to assess potential exposure. Radiation Safety In Dental Practice – A Study Guide | 5 of 69 cda.org/practicesupport e. Assure that records of occupational exposure must be made regularly. Records of individual monitoring must be retained for period of employment plus 30 years, per Cal/OSHA requirements (8 CCR §3204). Area monitoring records and health physicist reports should be kept for as long as facility is open. f. Assure that dental personnel do not stand in the path of the useful beam and must remain behind a protective shield or stand at least six feet away from the patient and between 90° - 135° to the direction of the primary beam during an exposure. g. Make or cause to be made such surveys and/or tests, including quality control (QC) tests, as are reasonable and necessary for the protection of life, health or property or are required by law or regulation. h. Report to the Radiologic Health Branch any dental personnel x-radiation overexposure in excess of the allowable occupational dose limits (see Section I.F.1 of this guide). i. Provide information to occupationally exposed individuals regarding health protection issues associated with exposure to radiation, precautions or procedures to minimize exposure, and the purpose and function of protective devices employed. These instructions should be given both verbally and in writing. C. Enforcement of Regulatory Prohibitions 1. Dental personnel during patient exposure may not do any of the following: • • • • • • Hold the patient Hold the image receptor, i.e., film, phosphor plate (PSP), CCD, or CMOS, in the patient’s mouth Hold X-ray tube housing, unless a valid exemption is in place and on file at the dental facility. Current exemptions may be found on the Radiologic Health Branch Web site at cdph.ca.gov/RHB. An exemption for hand-held X-ray units was issued in March 2013. Hold the aiming cylinder (also known as PID or pointer cone) Stand in the path of the useful X-ray beam Stand closer than six feet from the patient being radiographed 2. Dental personnel must not expose any individual to the useful beam for training or demonstration purposes without a valid X-ray prescription from a licensed dentist or a medical doctor stating a diagnostic need for the exposure. D. Compliance with Posting and Recordkeeping Requirements 1. Conspicuously post a current copy of the Department of Public Health Form RH-2364 (Notice to Employees) in a sufficient number of places to permit individuals working in an X-ray room to observe a copy on the way to or from the room. 2. In areas or rooms where X-ray equipment is used, post a sign (that may include the radiation symbol) stating: CAUTION X-RAYS 3. Provide annual report of occupational exposure to all individuals who are being monitored if requested. 4. Post or make available California Radiation Control Regulations or the excerpts of the regulations pertaining to dental practice. The excerpts are included as an appendix of this publication. 5. Post or make available safety instructions, restriction of the operating technique required for safe operation of the particular X-ray apparatus, and current copy of operating and emergency procedures. Radiation Safety In Dental Practice – A Study Guide | 6 of 69 E. cda.org/practicesupport Dental Personnel Training and Competency Evaluation 1. Establish that dental X-ray equipment and imaging software is operated only by individuals adequately instructed in safe operating procedures and who are competent in the safe use of the particular dental X-ray equipment and knowledgeable use of the software. 2. Verify that dental personnel have demonstrated familiarity with basic radiation safety rules as listed in Section 1.C., III and IV. 3. Maintain documentation of training and of evaluation of competent use of the X-ray equipment and imaging software. F. Compliance with Occupational Exposure Requirements 1. Maximum permissible dose equivalent (MPD). The essential goal of radiation safety is to prevent injury from exposure to ionizing radiation. For this reason, regulations have been established with the following annual occupational dose equivalent limits for adults who make radiographic exposures during the course of their work: • • • Whole body (total effective dose equivalent) – 5 rem or 0.05Sv Skin and extremities (shallow-dose equivalent) – 50 rem or 0.5 Sv Lens of the eye (eye dose equivalent) – 15 rem or 0.15 Sv The regulations distinguish the following: • • • • Occupational dose equivalent limits for adults (persons over 18 years of age) Occupational dose equivalent limits for persons under 18 years of age (may receive 10 percent of the adult occupational dose limits) Dose equivalent limits for general population Radiation dose to an embryo/fetus (prenatal radiation exposure) Exception: Radiation dose received for the operator’s own personal medical or dental diagnosis or medical therapy is not considered to be occupational exposure. If the dental hygienist or dental assistant is a patient, then he/she must remove the personnel monitoring device before being exposed. 2. Employees who are occupationally exposed at more than one facility. The annual exposure limit applies to all occupational doses that an individual receives during the year. If an employee is occupationally exposed to ionizing radiation at more than one facility, each employer has the responsibility to monitor the employee’s total occupational exposure to be sure that those dose limits are not exceeded. Since a dental facility has to either (1) provide personnel monitoring or (2) determine that occupationally exposed staff are not likely to exceed 10% of the annual limit, the employer should obtain from an employee who is occupationally exposed at more than one facility: • • A copy of a dosimetry report from each of the other employers (the reporting period should not exceed one year; a quarterly report is preferable); OR Documentation from another employer that has determined that its employees are not likely to receive greater than 10% of the annual exposure limit. Radiation Safety In Dental Practice – A Study Guide | 7 of 69 cda.org/practicesupport 3. Radiation dose limits for individual members of the public other than patients. Each licensed dentist shall conduct X-ray operations so that no individual member of the public will receive more than the maximum radiation dose in any unrestricted area as indicated: • • 0.1 rems (i.e., 100 millirems or 1mSv) in a year, or 0.002 rem (i.e., 2 millirems or 0.02mSv) in any one hour. Section II – Dental Radiographic Machine Requirements A. X-ray Tube Housing The X-ray beam is generated within a vacuum tube containing a cathode with a tungsten filament, and an anode “target,” usually made of copper and tungsten. The X-ray tube itself is enclosed in a metal housing, with a window (port) through which the useful or primary X-ray beam passes. The X-ray tube housing must be of a diagnostic type. A “diagnostic type tube housing” is the type of tube housing constructed so that leakage radiation does not exceed 100 mrems, or 1mSv, in any one hour at a distance of 1 meter (39.37 inches) from the X-ray tube. Note that this definition acknowledges that radiation can escape the X-ray tube housing from areas other than the window (port). B. Collimating Device – Restricting the Size of the X-ray Beam X-rays that extend beyond the area of the dental image receptor (i.e., film, PSP, CCD, or CMOS) serve no useful purpose and should be eliminated to the maximum extent practicable. The X-ray beam shall be restricted to a diameter of not more than 7 cm (2.75 inches) in diameter at the surface of the skin. This size of the X-ray beam is sufficient to allow for reasonable alignment errors. It is highly desirable to add a rectangular collimator that limits the X-ray beam to a size just larger than that of the dental image receptor used. This can be accomplished by either adding a rectangular collimator adapter to the aiming cylinder, replacing the aiming cylinder with a rectangular collimator model, or by incorporating a rectangular collimator into the film holding device. Restriction of the X-ray beam size reduces the total area of exposure and helps avoid exposure of sensitive areas, such as the lens of the eye, or the thyroid gland that are outside the area being examined for dental purposes. Clinically, reduction of the X-ray beam diameter improves the diagnostic quality of the image by lessening the amount of image degradation (fog) caused by scatter radiation. C. X-ray Beam Filtration The primary X-ray beam is made up of X-rays of different energies. Only the X-rays with higher energies can penetrate the tissue of the patient’s face and react with the image receptor area (i.e., film, PSPP, CCD, CMOS). Low-energy X-rays that have no effect on image production and are absorbed by the tissues, can cause tissue damage. A filter functions by absorbing preferentially more of the low-energy (long wavelength) X-rays before they reach the patient, while allowing more of the high-energy (short wavelength) X-rays to pass through. Some X-ray tubes within the X-ray tube head are surrounded by oil (except the “window” through which the useful or primary X-ray beam passes) for electrical insulation and to keep the X-ray tube from overheating. X-ray beam filtration is accomplished by placing a filter (usually aluminum) in the path of the useful or primary beam to absorb some of the low-energy X-rays before they reach the patient. The total filtration of an X-ray beam includes inherent filtration and the added filtration (discussed above). Inherent filtration, which is a permanent part of the X-ray tube, Radiation Safety In Dental Practice – A Study Guide | 8 of 69 cda.org/practicesupport includes the X-ray tube housing, the oil and the glass envelope (window) through which the primary or useful X-ray beam passes. The amount of inherent filtration produced by most diagnostic X-ray tubes usually ranges from 0.5 to over 2.0 mm aluminum-equivalent. Added filtration includes sheets of metal (usually aluminum) placed in the direct path of the X-ray beam between the port and the patient. Added filtration can be changed or modified, as required. Proper filtration for the dental X-ray unit is provided by the manufacturer and need not be modified in most cases. The regulations specify the minimum total filtration as shown below: Tube Operating Minimum Total Filter (inherent plus added) Potential (kV) (millimeters of aluminum or aluminum-equivalent) Below 50 50 to 70 71 and above 0.5 1.5 2.5 Diagnostic X-ray tubes use aluminum or an aluminum-equivalent as the filter material. (“Aluminum-equivalent” is defined as a substance equivalent to aluminum in its ability to absorb preferentially less penetrating radiation.) D. Exposure Cord The exposure switch must be permanently fixed in a safe shielded location or the exposure cord on a remote hand switch must be long enough to permit the operator to make exposures while positioned at least six feet from the patient. This six-feet distance must also be between 90°-135° to the direction of the primary X-ray beam. E. Exposure Timer The X-ray machine must have a device to terminate the exposure after a preset time or exposure. This is usually in the form of a “dead-man” type exposure switch. This type of switch requires constant pressure from the operator in order for the machine to function. F. X-ray Tube Head and Flexible Arm Assembly The flexible extension arm allows the X-ray tube head to be adjusted to various positions required for dental radiography. The mechanical support of the X-ray tube head and cone shall maintain the exposure position without drift or vibration. G. Portable X-ray Units 1. The portable dental X-ray system being used must have FDA approval and must be used in a manner consistent with that approval. 2. The unit must have a manufacturer-provided backscatter shield that is not less than 0.25 mm lead equivalent. The shield must be permanently affixed in place at all times. The X-ray system may not be used if this component becomes broken or dislodged. H. Cone Beam Computed Tomography (CBCT) Units Maintain these units following manufacturer’s recommendations. The units also should be tested by knowledgeable technicians on a periodic basis if not already part of the manufacturer’s recommendations. Radiation Safety In Dental Practice – A Study Guide | 9 of 69 cda.org/practicesupport Section III – Patient Protection A. Dental personnel are responsible for requiring that all individuals unnecessary to the dental radiographic examination leave the X-ray room prior to making an exposure. B. Anyone who is in the X-ray room at the time of exposure must be behind a protective barrier. If someone must also be in the room to assist or maintain patient safety, then this individual must wear a protective apron. The apron should be preferably 0.5 mm of lead or lead-equivalent but not less than 0.25 mm of lead or lead-equivalent thickness. Mobile protective barriers or shields should be available for dental personnel protection and should be used as indicated. C. A specially designed lead-impregnated thyroid collar can be used to protect the thyroid gland from excessive and/ or unnecessary radiation during intraoral X-ray exposures. It is also highly recommended for panoramic, skull and CBCT exposures if the Velcro straps can be secured and kept out of the way of the primary beam or it does not cover an area of primary interest (e.g., if cervical vertebrae need to be included in an extra-oral image.) D. Lead-impregnated leather or vinyl aprons must be used to cover the reproductive organs of all patients, including pregnant patients, who undergo dental X-ray examinations. The ability of the apron material to stop X-rays is measured in “lead-equivalent” thickness, that is equivalent to the same thickness of solid lead. Thus, 0.25 mm of lead-equivalent is equal to 0.25 mm of solid lead. Protective aprons are available which are constructed of a material of 0.5 mm of lead-equivalent and thus provide greater protection to the gonads. The lead-equivalent thickness is stated on a label on the hem of the apron. The American College of Obstetricians and Gynecologists recommends (August 2013) that dental practices reassure patients that prevention, diagnosis, and treatment of oral conditions, including dental X-rays (with shielding of the abdomen and thyroid) and local anesthesia (lidocaine with or without epinephrine), are safe during pregnancy. E. Aprons should be evaluated periodically (at least yearly) for tears and cracks. Seriously compromised aprons may have lead sheeting that is bunched up. This can be detected by feeling the lower portion of the apron. F. A more detailed evaluation can be accomplished with medical radiographic equipment by X-raying the apron using a large image receptor and making a routine exposure (recommended exposure factors: 85 kVp, 10 mAs, 40-inch focal-film distance) or under fluoroscopy. G. Proper storage of protective aprons prolongs their life and effectiveness. Aprons should be properly hung because creases eventually become cracks which allow radiation to penetrate. H. Protective aprons are primarily designed to protect the wearer from scatter radiation. They do not totally protect against the primary X-ray beam to provide enough protection. This is the reason why small beam (rectangular) collimation is preferred. The reduction in exposure resulting from placing 0.25 mm lead-equivalent apron material in a primary X-ray beam of 100 kVp would only be 60% as compared to 0.50 mm lead-equivalent apron that will attenuate the beam by 85%. Radiation Safety In Dental Practice – A Study Guide | 10 of 69 cda.org/practicesupport Section IV – Responsibilities of Dental Personnel Operating X-ray Equipment Dental personnel who perform dental radiography are responsible for adhering to all of the following radiation safety procedures for the protection of the patient and for their own protection. A. Protect Patient from Unnecessary Radiation Exposure Use appropriate protective devices, such as protective aprons, to cover patient’s reproductive organs and a protective lead collar to protect patient’s thyroid gland during exposure. Rectangular collimation of the X-ray beam is highly recommended as a means of decreasing the radiation dose to the patient. For procedures with CCD and CMOS receptors, prepare the computer and imaging software prior to intraoral receptor placement. This helps reduce technique errors and the need for technique related retakes. Taking the X-ray before the computer is prepared may expose the patient to unnecessary radiation. B. Use Fast Image Receptors Without sacrificing diagnostic quality, patient exposure may be reduced by more than 50 percent by changing to a faster film speed or to a digital image receptor. According to the FDA, “The facts that E- and F-speed film products offer significant exposure reduction compared with D-speed film, cost approximately the same and offer comparable clinical benefits strongly support a change of practice for those facilities that continue to use slow-speed film products that contribute to patients’ exposures which are greater than necessary.” fda.gov/downloads/Radiation-EmittingProducts/ RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/UCM329746.pdf Speed Ratings of Commonly Used Dental Films Film Brand Speed Group* Kodak Ultra Speed D AGFA-Dentus, Flow D Kodak Intraoral E AGFA-Dentus E/F Kodak Insight, Flow F Indirect Digital Image Receptors - PSPP n/a Direct Digital Image Receptors – CCD, CMOS n/a *American National Standards Institute C. Plan Dental Radiographic Procedures Carefully and Avoid Unnecessary Retakes Every examination that must be repeated results in excess patient radiation exposure. Retakes represent one of the greatest causes of excessive radiation exposure in dental radiography. Obtaining a quality dental radiographic image is a complex process demanding careful attention to many details. Radiation Safety In Dental Practice – A Study Guide | 11 of 69 cda.org/practicesupport 1. Five of the most important factors relating to the production of quality radiographs are: • • • • • Patient positioning and instruction Alignment of the X-ray beam and the film, or sensor, with the area to be radiographed Use of rectangular collimating device Selection of proper exposure factors (kV, mA, time, distance) Proper film or digital image processing 2. As much as practical, the long axis of the body part being radiographed should be perpendicular to the main X-ray beam (called central ray or CR) and parallel to the image receptor (paralleling technique). 3. Use proper immobilization methods to assure that the patient does not move during exposure. Receptor holding instruments with beam alignment devices should be used instead of the patient retaining the image receptor with fingers. 4. Use an exposure time that is as short as possible to minimize the radiation dose and motion artifact during exposure. 5. Ensure that the focal spot-to-film distance (FFD) is correct. Modern machines have recessed tubes with FFD ranging from 8 to 12 inches. Research has shown 8-inch (20 cm) FFD produces adequate images with minimum absorbed dose to the patient. 6. All patient exposures procedures must be documented in the patient’s record and the images should be properly labeled. 7. The diagnostic information obtained from the radiographic images also should be recorded in a notation or formal report in the patient’s record. D. Using Proper Kilovoltage (kV) Kilovoltage determines the penetrating ability (quality) of the X-ray beam. To a lesser extent it also determines the quantity of X-rays in the X-ray beam. When a high kV is used in a film system, there will be more shades of gray (i.e., low contrast) than when low kV is used. Most of the newer dental X-ray units have fixed milliamperage (mA) and/or fixed kilovoltage (kV). Thus, in such instances the variable factors are: exposure time, target-to-receptor distance and the speed of the image receptor. E. Milliamperage (mA) and Time Setting Milliampere-seconds (mAs) determines the amount (quantity) of x-radiation being produced. The mAs factor is calculated by multiplying the milliamperage (mA) x time (in seconds) = mAs (milliampere-seconds). A common practice is to set the mA at the highest setting available on the particular dental X-ray machine and then establish the proper timer settings. This technique results in the use of shorter time settings, which are helpful in avoiding patient motion artifacts on the radiograph. F. Protecting the Operator from Unnecessary Radiation Exposure 1. Individuals who are occupationally exposed to radiation are not permitted to hold patients or to hold image receptors during exposure; nor shall any individual be regularly used for this service. Radiation Safety In Dental Practice – A Study Guide | 12 of 69 cda.org/practicesupport 2. During the exposure, dental personnel who perform dental radiography should stand behind a protective barrier. In situations where dental personnel cannot stand behind a protective barrier, they must stand at least 6 feet away from the patient and the X-ray tube, not in the path of the primary beam but preferably behind a fixed or mobile barrier such as a lead-shielded wall or movable leaded Plexiglass shield. [17CCR 30311(b)(2)] 3. Increase the distance between the patient (the source of scatter radiation) and the X-ray operator to over 6 feet. The intensity of the primary X-ray beam, scatter radiation and leakage from the X-ray tube diminishes rapidly as the distance between the dental X-ray operator and the source of radiation (or the patient) increases. The degree of beam intensity reduction is related exponentially to the second power of the changes in the distance. If a dental X-ray operator can increase his or her distance from the radiation source by a factor of 2, his or her exposure would be reduced to ¼ of the original amount. 4. Hand-held dental radiographic machines must have the backscatter shield provided by the manufacturer, which provides not less than 0.25 mm lead equivalent, permanently affixed in place at all times. The X-ray machine may not be used if this component becomes broken or dislodged. The operator may wear a lead apron for additional protection however, this measure is not required. Radiation Safety In Dental Practice – A Study Guide | 13 of 69 cda.org/practicesupport Section V – Dental Radiographic Quality Assurance (QA) and Quality Control (QC) Quality assurance (QA) program should include the X-ray and ancillary imaging equipment, education of dental personnel to perform quality control (QC), and preventive maintenance procedures. To complete the daily QC at the beginning of the work day does not take more than five to ten minutes of dental personnel time. The primary cost saving of a QA program is related to the decreased need for repeat studies. The cost savings include reduction in: • • • Downtime of equipment Dental personnel time Cost of equipment service Film The state Department of Public Health in 2012 adopted regulations for quality assurance for X-ray film processing. The regulations implement legislation that was intended to apply to all types of radiographic equipment. The department, in its supporting documents for the regulations, stated that it hoped to develop regulations for digital equipment in the future “when standards have been established, accepted, or published by a nationally recognized radiation protection organization.” Quality assurance (QA) equipment for dental film processing includes: • • Thermometer (dial, digital or electronic but no alcohol or mercury because these may break and contaminate processing solutions). Step wedge (or a sensitometer and densitometer). An aluminum step wedge, acquired from an X-ray accessories supplier or provided by a service representative. A typical protocol for using a step wedge for checking processing solutions is as follows: 1. Expose 15 to 20 films with a step wedge using identical exposure factors (same time, kV and mA for a molar projection) and focal film distance. 2. Process one film in a recently cleaned processor with fresh chemicals. This film will be used as a standard for comparison. 3. Place the remaining films in a cool, dry place, protected from any radiation sources. 4. Process one of these remaining exposed test films daily and compare with the standard film. 5. If differences are noted between the test film and standard film, these can be attributed to faulty processing conditions (usually exhausted chemistry), film fog, or inconsistent exposure. 6. Each time solutions are changed, evaluation of the processing system should be done. The standard film can also be used on a monthly basis as a comparison to detect changes in the exposure factors of an X-ray unit, if changes in density or contrast are noted. Radiation Safety In Dental Practice – A Study Guide | 14 of 69 cda.org/practicesupport When using intra-oral film for dental radiography, the following shall be done: 1. A reference film meeting the interpreting dentists’ criteria for image density, contrast, sharpness and overall quality is selected for use in daily comparisons of dental radiographs. 2. For each day dental radiographs are processed, clinical radiographs are compared to the selected reference film for density, contrast, sharpness, and overall image quality. 3. Corrective action is taken when observable changes occur in clinical radiographic image density, contrast, sharpness and overall quality. 4. Records of the corrective actions taken, and the effectiveness of those corrective actions, are maintained for a minimum of one year from the date the corrective action was taken. Appendix III of this guide includes information on dental film processing. Digital Quality assurance for digital receptors are necessary just as conventional films. Since the phosphor plates and digital sensors are used repetitively, greater care in cleaning and handling is necessary. There should be periodic examination for digital receptors (whether PSP or direct sensors ) for scratching, bend marks, wear and tear or if the same artifacts appear on the images. Worn imaging plates (PSPs) with scratch marks or artifacts which detracts from image quality must be discarded and replaced with new ones. Wire connections for direct digital sensors should be examined and inspected. Any further performance testing should be done in accordance with the manufacturer. Use of a step-wedge with digital receptors (sensors or phosphor plates) can also be part of a daily routine to confirm that computer imaging software is working properly prior to any patient exposure. Radiation Safety In Dental Practice – A Study Guide | 15 of 69 cda.org/practicesupport Section VI – Equipment QA Requirements (General Provisions) All equipment used for producing quality, diagnostic radiographs should be checked periodically to insure optimum performance. Due to the sensitive nature of the tests and the cost of the testing equipment, a qualified service representative for the type of dental X-ray unit needing evaluation should be contacted to perform the necessary tests. Periodic testing should include X-ray output, half value layer, mA and kV calibration, timer accuracy, and collimation and beam alignment. Tube head stability should be checked at least monthly. Extend the arm of the X-ray unit fully, release the unit and observe for drift or vibration. Move the head to multiple locations and angulations and repeat the procedure. If any drift is noted, adjust the unit according to the manufacturer’s instructions or have the service performed by a qualified technician. Radiation Safety In Dental Practice – A Study Guide | 16 of 69 cda.org/practicesupport Section VII – Guidelines for Prescribing Dental Radiographs The joint FDA-ADA guidelines (2012) are designed to ensure continuous radiographic surveillance for caries, alveolar bone loss associated with periodontal disease, periapical disease and other latent pathology. The use of patient selection criteria insures that each patient exposure will have maximum diagnostic benefit. Patient selection criteria are descriptions of clinical conditions derived from patient signs, symptoms and history that identify patients who are likely to benefit from a particular radiographic examination. These guidelines were developed by a panel of general dentists and specialists sponsored by the FDA and were the result of a review of the many studies available on the incidence and progression rates of caries, periodontal disease, growth and development assessment and latent pathology. The guidelines were first developed in 1987 and have been revised in 2004 and 2012. The guidelines categorize patients first by type of visit (new or recall), then by dental status (child with primary or transitional dentition, adolescent, or adult dentulous or edentulous). Lastly the patient’s risk category for caries, periodontal disease or growth and development assessment is considered. Use of these guidelines should promote the appropriate use of X-rays, by reducing overutilization and excessive radiation, and minimizing underutilization of imaging with potential inadequate diagnosis. The full guidelines document, Dental Radiographic Examinations: Recommendations for Patient Selection and Limiting Radiation Exposure, is available on the FDA Web site, fda.gov/Radiation-EmittingProducts/ RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-rays/ucm116504.htm. Cone beam CT imaging should be considered for cases in which intraoral or panoramic imaging are inadequate for proper diagnosis and/or treatment. The following position statements serve as guidelines for CBCT use in dentistry: • • • • The use of cone-beam computed tomography in dentistry: An advisory statement; American Dental Association, JADA August 2012, jada.ada.org/issue/S0002-8177(14)X6067-8 Use of cone beam computed tomography in endodontics 2015 update; A joint position statement of the American Association of Endodontists and the American Academy of Oral and Maxillofacial Radiology aae.org/specialty/wp-content/uploads/sites/2/2017/06/conebeamstatement.pdf Position statement of the American Academy of Oral and Maxillofacial Radiology on selection criteria for the use of radiology in dental implantology with emphasis on cone beam computed tomography, June 2012, ncbi.nlm.nih.gov/pubmed/22668710 Clinical recommendations regarding use of cone beam computed tomography in orthodontics. Position statement by the American Academy of Oral and Maxillofacial Radiology. In Oral Surg Oral Med Oral Pathol Oral Radiol 2013: 116:238-257, oooojournal.net/article/S2212-4403%2813%2900280-0/. Cone beam CT images performed by or under the supervision of a licensed dentist may be performed only for dental diagnosis or treatment and may not be performed for any other purposes. Radiation Safety In Dental Practice – A Study Guide | 17 of 69 cda.org/practicesupport Excerpt from FDA/ADA Dental Radiographic Examinations: Recommendations for Patient Selection and Limiting Radiation Exposure (2012) ada.org/~/media/ADA/Member%20Center/FIles/Dental_Radiographic_Examinations_2012.pdf Recommendations for Prescribing Dental Radiographs These recommendations are subject to clinical judgment and may not apply to every patient. They are to be used by dentists only after reviewing the patient’s health history and completing a clinical examination. Even though radiation exposure from dental radiographs is low, once a decision to obtain radiographs is made it is the dentist’s responsibility to follow the ALARA Principle (As Low as Reasonably Achievable) to minimize the patient’s exposure. Table 1 Patient Age and Dental Developmental Stage Type of Encounter Child with Primary Dentition (prior to eruption of first permanent tooth) Child with Transitional Dentition (after eruption of first permanent tooth) Adolescent with Permanent Dentition (prior to eruption of third molars) New Patient* being evaluated for oral diseases Individualized radiographic exam consisting of selected periapical/ occlusal views and/or posterior bitewings if proximal surfaces cannot be visualized or probed. Patients without evidence of disease and with open proximal contacts may not require a radiographic exam at this time. Individualized radiographic exam consisting of posterior bitewings with panoramic exam or posterior bitewings and selected periapical images. Individualized radiographic exam consisting of posterior bitewings with panoramic exam or posterior bitewings and selected periapical images. A full mouth intraoral radiographic exam is preferred when the patient has clinical evidence of generalized oral disease or a history of extensive dental treatment. Recall Patient* with clinical caries or at increased risk for caries** Posterior bitewing exam at 6-12 month intervals if proximal surfaces cannot be examined visually or with a probe Posterior bitewing exam at 6-18 month Not applicable intervals Recall Patient* with no clinical caries or at increased risk for caries** Posterior bitewing exam at 12-24 month intervals if proximal surfaces cannot be examined visually or with a probe Posterior bitewing exam at 24-36 month intervals Posterior bitewing exam at 18-36 month intervals Adult, Dentate or Partially Edentulous Adult, Edentulous Individualized radiographic exam, based on clinical signs and symptoms. Not applicable Radiation Safety In Dental Practice – A Study Guide | 18 of 69 cda.org/practicesupport Table 1 (con’t.) Patient Age and Dental Development Stage Type of Encounter Recall Patient* with periodontal disease Patient (New and Recall) for monitoring of dentofacial growth and development, and/or assessment of dental/skeletal relationships Child with Primary Dentition (prior to eruption of first permanent tooth) Child with Transitional Dentition (after eruption of first permanent tooth) Adolescent with Permanent Dentition (prior to eruption of third molars) Adult, Dentate or Partially Edentulous Clinical judgment as to the need for and type of radiographic images for the evaluation of periodontal disease. Imaging may consist of, but is not limited to, selected bitewing and/or periapical images of areas where periodontal disease (other than nonspecific gingivitis) can be demonstrated clinically. Clinical judgment as to need for and type of radiographic images for evaluation and/or monitoring of dentofacial growth and development or assessment of dental and skeletal relationships Clinical judgment as to need for and type of radiographic images for evaluation and/ or monitoring of dentofacial growth and development, or assessment of dental and skeletal relationships. Panoramic or periapical exam to assess developing third molars Adult, Edentulous Not applicable Usually not indicated for monitoring of growth and development. Clinical judgment as to the need for and type of radiographic image for evaluation of dental and skeletal relationships. Patient with other circumstances including, but not limited to, proposed or existing implants, other dental Clinical judgment as to need for and type of radiographic images for evaluation and/or monitoring and craniofacial of these conditions pathoses, restorative/ endodontic needs, treated periodontal disease and caries remineralization *Clinical situations for which radiographs may be indicated include, but are not limited to: Radiation Safety In Dental Practice – A Study Guide | 19 of 69 A. Positive Historical Findings 1. Previous periodontal or endodontic treatment 2. History of pain or trauma 3. Familial history of dental anomalies 4. Postoperative evaluation of healing 5. Remineralization monitoring 6. Presence of implants, previous implant-related pathosis or evaluation for implant placement B. Positive Clinical Signs/Symptoms 1. Clinical evidence of periodontal disease 2. Large or deep restorations 3. Deep carious lesions 4. Malposed or clinically impacted teeth 5. Swelling 6. Evidence of dental/facial trauma 7. Mobility of teeth 8. Sinus tract (“fistula”) 9. Clinically suspected sinus pathosis 10. Growth abnormalities 11. Oral involvement in known or suspected systemic disease 12. Positive neurologic findings in the head and neck 13. Evidence of foreign objects 14. Pain and/or dysfunction of the temporomandibular joint 15. Facial asymmetry 16. Abutment teeth for fixed or removable partial prosthesis 17. Unexplained bleeding 18. Unexplained sensitivity of teeth 19. Unusual eruption, spacing or migration of teeth 20. Unusual tooth morphology, calcification or color 21. Unexplained absence of teeth 22. Clinical tooth erosion 23. Peri-implantitis **Factors increasing risk for caries may be assessed using the ADA Caries Risk Assessment forms (0-6 years of age and over 6 years of age) ada.org/~/media/ADA/Member%20Center/FIles/topics_caries_under6.pdf?la=en ada.org/~/media/ADA/Science%20and%20Research/Files/topic_caries_over6.pdf?la=en cda.org/practicesupport Radiation Safety In Dental Practice – A Study Guide | 20 of 69 cda.org/practicesupport Section VIII – Occupationally Exposed Women of Childbearing Age California Radiation Control Regulations state that each licensed dentist must instruct occupationally exposed individuals (dental hygienists and dental assistants) in the health protection problems associated with radiation. A special situation arises with occupationally exposed young women. The precautions should be taken to limit exposure to young women, especially if they could be pregnant. X-ray exposure to the abdomen of such workers would involve radiation dose to the embryo or fetus in the event that they are pregnant. Licensed dentists are responsible for the following: • • • • • Following Nuclear Regulatory Commission Regulation requirements (10 CFR Part 20) incorporated in California Regulations by reference) at Title 17, Section 30253. Providing individual or personal monitoring devices to occupationally exposed individuals if they are likely to receive 10% of the annual limits in 10CFR20 section 20.1201(a). Providing individual or personal monitoring devices to occupationally exposed declared pregnant individuals if they are likely to receive during the entire pregnancy a deep dose equivalent in excess of 0.1 rem (1 mSv). Providing the employee with reasons for the requirements. (See below) Explaining the available options for protecting the embryo/fetus. (See below) A. Dose to an embryo/fetus 1. Definitions: Declared pregnant woman means a woman who has voluntarily informed her employer, in writing, of her pregnancy and the estimated date (month) of conception. Deep-dose equivalent, which applies to external whole-body exposure, is the dose equivalent at a tissue depth of 1 cm (100 mg/cm2). Embryo/fetus means the developing human organism from conception until the time of birth. 2. Regulatory provisions (10CFR20): a. The licensed dentist shall ensure that the dose to an embryo/fetus during the entire pregnancy, due to occupational exposure of a declared pregnant woman, does not exceed 0.5 rem (5 mSv). b. The licensed dentist shall make efforts to avoid substantial variation above a uniform monthly exposure rate to a declared pregnant woman so as to satisfy the limit in paragraph (a) of this section. c. The dose to any embryo/fetus shall be taken as the deep-dose equivalent to the declared pregnant woman. d. If the dose to an embryo/fetus is found to have exceeded 0.5 rem (5 mSv), or is within 0.05 rem (0.5 mSv) of this dose, by the time the woman declares the pregnancy to the licensed dentist, the dentist shall be deemed to be in compliance with paragraph (a) of this section if the additional dose to the embryo/fetus does not exceed 0.05 rem (0.5 mSv) during the remainder of the pregnancy. B. Reasons for requirements Some studies have shown that there is an increased risk of leukemia and other cancers in children if the expectant mother was exposed to a significant amount of radiation. Women employees must be aware of possible risks so they can take appropriate steps to protect their offspring. Radiation Safety In Dental Practice – A Study Guide | 21 of 69 cda.org/practicesupport It is strongly suggested that the instruction be given both orally and in writing. Also each woman employee should be given an opportunity to ask questions, and each woman employee should be asked to acknowledge in writing that the instruction has been received. Further, it would be prudent to keep records of such acknowledgment indefinitely. The following facts should be given to the woman employee: • • • • • The first three months of pregnancy are the most important as the embryo-fetus is most sensitive to radiation at this time. In most cases of occupational exposure, the actual dose received by the embryo-fetus is less than the dose received by the mother, because some of the dose is absorbed by the mother’s body. At the present occupational dose equivalent limits, the risk to the unborn baby is considered to be small, but experts disagree on the exact amount of risk. There is no need for women to be concerned about sterility or loss of ability to bear children from occupational exposure. Once a pregnancy becomes known, radiation dose of the embryo-fetus shall be no greater than 0.5 rem (5mSv) for the entire pregnancy. Special circumstances apply if the pregnant worker has already exceeded this dose prior to declaring her pregnancy (See Section VIII A.2.d of this document). C. Available options for protecting embryo/fetus • • • • • Temporary assignment to tasks which involve less risk of being exposed to radiation Use of protective apron (full size, half-size, wrap-around, or any other protective clothing appropriate to the situation) while actually exposing patients Abiding by the regulatory prohibitions Use of monitoring devices such as a film badge worn at the abdomen Staying out of the X-ray room and behind the protective barrier during exposure Radiation Safety In Dental Practice – A Study Guide | 22 of 69 cda.org/practicesupport Section IX – Dental Radiation Protection – Protective Barriers A discussion on protective barriers is found in the National Council on Radiation Protection and Measurements (NCRP) Report No. 145, Radiation Protection in Dentistry (2003). A. General The objective of dental radiography is to obtain diagnostic quality dental radiographs with minimum exposure to the patient, dental personnel and the public. Efforts toward these objectives include: • • • • Use of the fast film (F-speed) or digital image receptors Maintenance and adherence to proper film processing Assurance of adequate and proper X-ray tube filtration, kV, mA and time accuracy through regular maintenance and calibration by a qualified service technician Operator protection (standing behind a protective barrier during exposure) B. Barriers Conventional building materials in walls, partitions, floor and ceiling may provide adequate shielding from x-radiation; however, there may be situations where lead shielding would be required due to workload, office design or other circumstances. The Radiologic Health Branch recommends that the shielding design for your particular situation be developed by a qualified expert, an individual knowledgeable in evaluating dental radiation protection requirements. A list of individuals and/or companies who perform such services is available from the Radiologic Health Branch: Department of Public Health Radiologic Health Branch P.O. Box 997414, MS 7610 Sacramento, CA 95899-7414 cdph.ca.gov/Programs/CEH/DRSEM/Pages/RHB.aspx Generally, a wall made of two layers of 5/8” offset gypsum board can be assumed to provide the minimum protection from scatter radiation if the following conditions are met: 1. Areas occupied by patients are protected by this wall or a wall of equivalent attenuating material, and there is at least a 6 feet distance between the dental X-ray chairs. 2. Dental personnel should be careful not to aim the primary beam toward areas adjacent the X-ray room. 3. The use of dental X-ray equipment does not exceed the following operating parameters: • • 60 seconds/week of actual beam “on-time” at 90 kVp, or 100 seconds/week of actual beam “on-time” at 65 kVp NOTE: If your X-ray facility is located in one of the following counties, you must contact that county’s Radiation Control Office prior to construction or remodeling of your X-ray operatory. Los Angeles County: (213) 351-7391 San Diego County: (619) 694-2169 Radiation Safety In Dental Practice – A Study Guide | 23 of 69 cda.org/practicesupport Section X – Glossary of Terms Pertaining to Dental Radiography Absorbed Dose: See Dose. Absorption (differential, rare earth screen, specific rate of, visible light): The transfer of energy from an X-ray beam to the atoms or molecules of the matter through which it passes. The process whereby radiation is stopped and reduced in intensity as it passes through matter. Lead, which is denser than most materials, is one of the best absorber of X-rays. Added Filter: See Filter. Aiming Cylinder: A round/circular metal tube/shield attached to the X-ray tube housing or placed in front of the X-ray tube to limit the size of the X-ray beam to a predetermined size and shape. ALARA: An acronym for As Low As Reasonably Achievable, economic and social factors being taken into consideration. Relates to radiation dose to the patients, the public, and occupationally exposed individuals. Aluminum Equivalent: The thickness of aluminum affording the same attenuation, under specified conditions, as the material in question. Anode: A positive electrode, also referred to as a target, toward which electrons are accelerated from the cathode. The target is usually composed of tungsten. Artifact: Any density or mark on a radiograph caused by something not belonging to the part being X-rayed. Attenuation: The process by which an X-ray beam is reduced in intensity by absorption or scattering when passing through material. Barrier, Protective: Barrier of attenuating materials used to reduce radiation exposure. Barrier, Primary: Barrier sufficient to attenuate the useful beam to the required degree. Barrier, Secondary: Barrier sufficient to attenuate scatter (i.e., stray) radiation to the required degree. Beam: A unidirectional flow of electromagnetic radiation. Primary Radiation or X-ray Beam: That part of the radiation which passes through the window, aperture, cone, or other collimating device of the tube housing. Also called “useful beam.” Bone marrow: A soft tissue which constitutes the central filling of many bones and serves to produce blood cells, including erythrocytes, leukocytes, thrombocytes, etc. Bone marrow is especially sensitive to X-rays. Cataract: a clouding of crystalline lens of the eye which obstructs the passage of light. Cathode: A negative electrode; electrode in the X-ray tube from which electrons are emitted. It consists of one or two tungsten filaments and a focusing cup. Centigray: 0.01 Gray (Gy). 1 cGy equals 1 rad. Central Ray (Central Beam): Refers to the X-rays in the center of the useful or primary beam. Characteristic Curve: A type of input-output curve used to express the change in density with the change in radiation dose (exposure) of photographic or X-ray film. The slope of the straight line portion of this curve is called “gamma.” Charge-Coupled Device (CCD): Direct digital image receptor (sensory that forms images on a silicon crystal pixel matrix which automatically transfers data to a computer. Chromosome: Important macromolecules found in the nucleus of all body cells. Chromosomes contain the genes of heredity-determining units. Chronic Exposure: Irradiation which is spread out over a period of years. Those who are occupationally exposed to radiati