Consumer and Clinical Radiation Protection Bureau Environmental and Radiation Health Sciences Directorate Healthy Environments and Consumer Safety Branch Health Canada 2022 ISBN: 978-0-660-43152-9 Show
Cat No.: H129-131/2022E-PDF Table of ContentsOverviewSafety Codes are a series of documents prepared by Health Canada to provide radiation protection guidance. They help promote consistency in radiation protection practices to support the safe use of radiation emitting devices in Canada. This document supersedes the previous version of Safety Code 30, entitled "Radiation Protection in Dentistry: Recommended Safety Procedures for the Use of Dental X-ray Equipment," which was published in 1999. The updates in this version address new dental X-ray technologies, such as hand-held devices, cone beam computed tomography and the introduction of digital image receptors replacing the use of film. These technological advancements, along with new international guidance and standards applicable to dental radiography, necessitate updates to radiation protection requirements and practices. Safety Codes provide radiation protection guidance, information and advice. Health Canada's Safety Codes are sometimes referenced in regulations, standards and policies of other authorities, such as federal, provincial or territorial government departments and agencies. In those situations, the applicable department or regulatory authority determines how compliance with the Safety Code is verified. For example, Safety Code 30 is referenced in the Canada Occupational Health and Safety Regulations for the instruction and guidance of persons employed in Federal Public Service departments and agencies, as well as those whose employers are under the jurisdiction of the Canada Labour Code. Rules governing the safe installation and use of X-ray equipment, as well as protocols and safety requirements for operators, may be established through provincial and territorial legislation, professional orders and associations. This may include requirements relating to who can perform specific actions or fulfill the roles and responsibilities outlined in this Safety Code. In some cases, provincial/territorial authorities may also reference Health Canada Safety Codes. The authorities listed in Appendix I should be contacted for details of the regulatory requirements of individual provinces and territories and to determine the applicability of this Safety Code. Who this safety code is forThe information in this Safety Code has been prepared to provide guidance to the owners of dental facilities, dentists, dental hygienists, dental therapists, dental assistants, radiation/X-ray safety officers and other individuals or organizations concerned with radiation safety procedures, equipment performance, and radiation protection for the use of dental X-ray equipment. Principle objectives of this safety codeThis Safety Code sets out principles and best practices to help ensure radiation protection of all individuals who may be exposed to radiation from dental X-ray equipment. It provides dental facilities with the necessary information to achieve the following principal objectives:
To assist in meeting these objectives, this Safety Code:
Scope and limitationsThis Safety Code provides radiation protection guidance for the safe installation and use of conventional and hand-held intra-oral dental X-ray equipment, as well as panoramic, cephalometric and conebeam computed tomography extra-oral dental X-ray equipment. It supersedes the previous version of Safety Code 30, entitled "Radiation Protection in Dentistry: Recommended Safety Procedures for the Use of Dental X-ray Equipment," which was published in 1999. The words must and should in this Safety Code have been chosen with purpose. The word must is used to indicate essential radiation protection requirements, while should indicates an advisory recommendation that is highly desirable and is to be implemented where possible. As technology continues to advance, it should be noted that this Safety Code cannot cover all possible situations. Over time, it will be reviewed and revised, and a particular requirement may be reconsidered at any time if it becomes necessary to address unforeseen situations. Recommendations may be modified in atypical circumstances, but only upon the advice of the relevant authorities and/or experts in radiation protection or dental radiography quality assurance. Interpretation or elaboration on any point can be obtained by contacting the Consumer and Clinical Radiation Protection Bureau, Health Canada (Appendix I). This Safety Code does not address other aspects of health and safety applicable to dental radiography (e.g. infection control practices). In this safety codeThis Safety Code is composed of three sections: Responsibilities and Protection, Facility and Equipment Requirements and Quality Assurance Program. Section A: Responsibilities and protection This section sets out the responsibilities of the owner, the coordinator of the radiation protection program, the X-ray equipment operator, the prescribing dental practitioner, the expert in radiation protection, and repair and maintenance personnel for the safe installation, operation and control of the equipment. It also sets out practices to minimize radiation doses to patients, staff and the public. Section B: Facility and equipment requirements This section sets out requirements for the facility design and minimum equipment construction and performance standards. Section C: Quality assurance program This section sets out requirements for quality assurance programs including acceptance testing and quality control procedures. The contents of this document are built upon and generally align with existing Canadian and international standards and guidelines. This includes Schedule II, Part II of the Radiation Emitting Devices Regulations, which regulates the construction and functioning of dental X-ray equipment, and international guidance documents such as the National Council on Radiation Protection and Measurements (NCRP) Report No. 145 and Report No. 177 (Radiation Protection in Dentistry), the European Commission (EC) Issue No. 136 (European guidelines on radiation protection in dental radiology), and International Electrotechnical Commission (IEC) standards for dental X-ray equipment. IntroductionDental radiography is one of the most valuable tools used in dental health care. It is used in the diagnosis of physical conditions that would otherwise be difficult to identify, as well as to assist in the planning of treatment. In the past twenty years, there have been numerous technological advances in dental radiography, including the introduction of digital image receptors replacing the use of film, cone beam computed tomography equipment, and hand-held X-ray devices. The radiation dose from a properly conducted dental X-ray procedure is generally low in comparison to other medical imaging modalitiesFootnote 1, Footnote 2, Footnote 3, and the annual dose received from natural background radiation4. While the science of low dose radiation is evolving, the current radiation protection risk model assumes that any radiation exposure may cause stochastic health effects (namely cancer), the probability of which is proportional to the doseFootnote 4, Footnote 5; therefore, any procedure involving exposures to ionizing radiation must be carefully managed. The radiological protection community recommends the use of the ALARA (As Low As Reasonably Achievable) principle. This approach to radiation protection manages and controls exposures to personnel and the general public to as low as is reasonably achievable, taking into account social and economic factors. The health risk associated with well-conducted dental X-ray procedures is typically very small and the benefit of appropriately justified imaging for directing patient care far outweighs these risks. There are four main aspects of radiation protection to be considered in dental radiography:
While in some cases regulatory dose limits have been established for occupationally-exposed personnel and the general public, these limits do not apply to doses received by a patient undergoing medical X-ray procedures. For patients, the risk associated with the exposure to radiation must always be weighed against the clinical benefit of an accurate diagnosis or treatment. There must always be a conscious effort to reduce patient doses to the lowest practical level consistent with optimal quality of diagnostic information. Through close cooperation between prescribing dental practitioners, the coordinator of the radiation protection program, X-ray equipment operators, experts in radiation protection, and any other support staff, it is possible to achieve an effective radiation protection program and maintain a high quality dental radiography program. Dental X-ray modalitiesThis section describes the types of dental X-ray technologies that are covered in this Safety Code. Intra-oralIntra-oral dental radiography consists of an image receptor that is placed inside the mouth of the patient, while the X-ray source is positioned outside the mouth. The X-ray beam must pass through the targeted area of the patient to reach the image receptor. The image receptor should be placed in a positioning device which aids in alignment of the cone of the X-ray source assembly. The images produced by intra-oral equipment are projection radiographs. Intra-oral radiographs are the most common type of dental radiographs. Conventional For conventional intra-oral equipment, the X-ray source is attached to a movable positioning arm that is mounted on the wall. The control panel and irradiation switch are generally affixed to a wall, which is not in the path of the primary beam, at a distance of greater than 2 m from the X-ray source assembly, or behind appropriate shielding. Transportable Transportable refers to equipment that is intended to be moved from one place to another, whether or not it is connected to a power supply and without an appreciable restriction of range. Transportable intra-oral equipment can be mounted on a stand with a corded or remote irradiation switch that allows the operator to stand more than 2 m from the X-ray source assembly. Mobile equipment is a subset of transportable equipment; it is intended to be moved from one location to another while supported by its own means, such as a mechanical stand on wheels. Hand-held Hand-held intra-oral equipment is a type of transportable equipment that can be held in the hand of the operator, while in operation, and can also be placed on a stand and operated with a corded or remote irradiation switch. Hand-held equipment must only be held by hand when it is not reasonably feasible for it to be supported on a stand and used remotely with the corded or remote irradiation switch. Extra-oralExtra-oral dental radiography consists of the X-ray source and the image receptor both being outside of the mouth of the patient. Unlike intra-oral radiography, the X-ray beam must pass fully through the patient to reach the image receptor. Extra-oral radiography consists of three modalities: Panoramic Panoramic radiography is a form of linear tomography where the X-ray source and image receptor rotate synchronously around the head of the patient to produce a two-dimensional radiograph for the entire dentition, or a portion thereof. The X-ray beam is collimated to a thin vertical strip. Only a thin area (the focal trough) around the teeth is in focus, while anatomy in front of or behind the teeth is blurred. For film panoramic images, the focal trough is defined by the coordinated movement of the rotating X-ray source and horizontal translation of the image receptor. Cone beam computed tomography Cone Beam Computed Tomography (CBCT) is a volumetric radiography technique where the X-ray source and image receptor rotate around the head of the patient acquiring many two-dimensional radiographic views. These views are combined using a computer to produce a three-dimensional image. The volume can also be viewed as a series of two-dimensional tomographic slices. Some CBCT machines can generate panoramic images and other reconstructed views (e.g. lateral and poste-anterior cephalometric images, and cross section views). Cephalometric Cephalometric radiography is a form of projection radiography where the image receptor remains stationary. The X-ray source is either stationary, in which case the X-ray exposure is a "snapshot" as in conventional medical radiography, or the X-ray source is a horizontally collimated thin beam that is scanned across the patient. Cephalometric radiography produces a two-dimensional projection radiograph of the patient. Section A: Responsibilities and protectionA.1.0 Responsibilities and qualifications of personnelAlthough staff responsibilities described below are grouped separately, to obtain the optimal level of radiation safety and image quality, it is imperative that full cooperation exists among all concerned parties. Provincial and territorial professional orders and regulations may also establish requirements relating to who can perform specific actions or roles outlined in this Safety Code, including the responsibilities and qualifications described in this section. The authorities listed in Appendix I should be contacted for details of the regulatory requirements of individual provinces and territories. A.1.1 OwnerThe responsibility for radiation safety of a dental facility rests with the owner. The owner is defined as the person or group of persons in control of the possession and use of dental X-ray equipment. The owner may be an individual, a corporation, a district, a province or some other entity. The following section lists the specific radiation safety tasks which are the responsibility of the owner. The owner may delegate the tasks to qualified staff. How these tasks are delegated will depend on the number of staff members, the nature of the operation and on the number of dental X-ray units owned. A.1.1.1 Responsibilities of owner The owner is responsible for:
A.1.2 Coordinators of the radiation protection programThe coordinator of the radiation protection program may be the dentist or other qualified staff member. Some provincial/territorial jurisdictions have a regulatory requirement for an X-ray Safety Officer in dental facilities with X-ray equipment, thus in these jurisdictions the X-ray Safety Officer would be the coordinator. A.1.2.1 Qualifications for coordinator of the radiation protection program The coordinator of the radiation protection program must:
A.1.2.2 Responsibilities of the coordinator of the radiation protection program: The coordinator of the radiation protection program must: Procedures
Equipment and facility
Quality assurance & quality control program
Operator safety
Training
A.1.3 X-ray equipment operatorsA.1.3.1 Qualifications of X-ray equipment operators The X-ray equipment operator must:
A.1.3.2 Responsibilities of X-ray equipment operators All dental X-ray equipment operators have the responsibility of carrying out prescribed dental radiological procedures in a manner which does not cause any unnecessary exposures to patients, themselves, other workers and the public in the facility. All dental X-ray equipment operators must:
A.1.4 Prescribing dental practitionerA.1.4.1 Qualifications of prescribing dental practitioners The prescribing dental practitioner must:
A.1.4.2 Responsibilities of prescribing dental practitioners The prescribing dental practitioner is the individual authorized to prescribe dental X-ray procedures. The main radiation protection responsibility of the prescribing dental practitioner is to ensure that the use of X-rays is justified. Currently, dental therapists in all jurisdictions and dental hygienists in some jurisdictions are authorized by legislation to order X-ray examinations. In such cases, the responsibilities of the prescribing dental practitioner listed below would apply to those individuals. It is recommended to contact the appropriate provincial or territorial radiation safety agencies, listed in Appendix I, for information on any applicable provincial or territorial statutes or regulations. The prescribing dental practitioner must:
and should:
A.1.5 Expert in radiation protectionAn "Expert in radiation protection", as referenced throughout this Safety Code, is a person with extensive knowledge and expertise in radiation protection. For example, individuals in the following professions may have such expertise: medical physicist, biomedical engineer, radiation protection physicist, physical engineer, or radiation protection specialist. A.1.5.1 Qualifications of experts in radiation protection According to any professional designations they have, the expert in radiation protection must:
A.1.5.2 Responsibilities of experts in radiation protection The role of the expert in radiation protection is to support the owner and coordinator of the radiation protection program in ensuring radiation safety of the dental facility. Specific functions of such support are referenced by use of the term "Expert in radiation protection" throughout the guidance in this Safety Code, such as conducting facility radiation surveys, assessing the need for use of personal dosimeters, calculating facility shielding requirements, and performing optimization of doses from X-ray devices. A.1.6 Repair and maintenance personnelPersonnel in this group perform maintenance and repairs on dental X-ray generators, control systems, imaging systems and their operating software. This function may be contracted to an outside service provider, or to the equipment manufacturer. The repair and maintenance personnel must:
A.2.0 Procedures for minimizing radiation exposure to personnelThe guidance outlined in this Section is primarily directed toward occupational health protection. However, adherence to these procedures will also, in many instances, provide protection to visitors and other individuals in the vicinity of a dental facility with X-ray equipment. These safe work practices should be regarded as a minimum, to be augmented with additional requirements, when warranted, to cover special circumstances in particular facilities. To achieve optimal safety, operators of dental X-ray equipment must make every reasonable effort to keep radiation exposures to themselves and to others as far below the limits specified in Appendix II as achievable (i.e. ALARA). A.2.1 General requirements and recommendationsEquipment & room
Procedures - personnel
Procedures - patients
A.2.2 Requirements for hand-held dental X-ray devicesProvinces and territories may have specific requirements for the use of hand-held dental X-ray devices. Facilities that fall under provincial or territorial jurisdiction should consult the regulatory authority listed in Appendix I for their respective region to obtain detailed information on any provincial or territorial statutory or regulatory requirements. Conditions of use
Procedures
Training and education
A.3.0 Procedures for minimizing radiation exposure to patientsThe largest single contributor of man-made radiation exposure to the population is medical radiology, which includes dental radiology. In total, medical use of X-rays accounts for more than 90% of the total man-made radiation dose to the general populationFootnote 4. The risk to the individual patient from a single optimized dental X-ray examination is low relative to other medical imaging procedures and the benefit to each individual from a justified dental X-ray examination outweighs the risk. However, the risk to a population is increased by increasing the frequency of X-ray examinations and by increasing the number of persons undergoing such examinations. For this reason, it is important to minimize through proper justification the number of dental radiographs taken and the number of persons examined radiographically, as well as to optimize the doses associated with the examinations. To minimize the radiation risk, it is essential that patients only be subjected to justified radiological examinations and when a radiological examination is required, patients must be protected from excessive radiation during the examination. The guidelines for the protection of the patient, outlined in this section, are directed toward the prescribing dental practitioner and the X-ray equipment operator. They are intended to provide guidance for the elimination of unnecessary dental radiological examinations and for minimizing doses to patients when radiological examinations are necessary. A.3.1 Guidelines for the prescription of dental X-ray examinationsPrescribing a dental X-ray examination should be based on professional experience, judgment, and current prescribing guidelines. Unnecessary radiation exposures of patients can be significantly reduced by ensuring that all X-ray examinations are clinically justified. This can be done by adhering to certain basic recommendations as presented below.
The following documents provide additional guidance on prescription criteria for dental X-rays, and may be used to aid in assessing the need for dental radiography:
A.3.2 Guidelines for protecting the patient during dental X-ray examinationsNext to the elimination of unnecessary X-ray examinations, the most significant factor in reducing patient dose is ensuring that examinations are performed using proper technique. It is the responsibility of the operator and the prescribing dental practitioner to be aware of this and to know how to carry out a prescribed examination with the lowest practical dose to the patient. The guidelines that follow are intended to provide guidance to the operator and the prescribing dental practitioner in exercising their responsibility towards reduction of radiation exposure to the patient. A.3.2.1 General guidelines for dental X-ray examinations
A.3.2.2 Requirements and recommendations for intra-oral examinations
A.3.2.3 Requirements and recommendations for panoramic examinations
A.3.2.4 Guidelines for cone beam computed tomography examinations
A.3.3 Guidelines for optimizing dental X-ray examinationsAs part of the ALARA principle, it is important that presettings and techniques for dental X-ray devices are optimized for each procedure performed in the facility to ensure patient radiation doses are minimized. An optimized X-ray procedure uses the least amount of X-ray exposure required to create a diagnostically acceptable image. Optimization of dental X-ray devices, including ongoing periodic assessment after initial installations, must be done by the vendor or dental service provider through which the device was purchased, or by an expert in radiation protection. Optimization also requires cooperation and input from the dental practitioner who is authorized to interpret patient images. The guidelines in the subsequent section help ensure optimization of dental X-ray devices. A.3.3.1 General guidelines for all dental X-ray examinations
A.3.3.2 Guidelines for intra-oral examinations For intra-oral devices, the image receptor is typically not integrated with the X-ray generator. Loading factors for preset techniques available from the X-ray generator can therefore be further optimized for the specific imaging system being used. An optimized technique chart must be used to manually set techniques if none are integrated to the X-ray generator. The following guidance applies to optimization of intra-oral devices when paired with a specific imaging system:
A.3.3.3 Requirements and recommendations for extra-oral examinations For digital extra-oral X-ray devices, the image receptor is integrated with the X-ray generator, and the devices are typically operated using preset techniques with loading factors set by the manufacturer. The vendor or dental service provider through which the device was purchased, or a third party expert in radiation protection, must evaluate the preset techniques for optimization based on the results of acceptance testing of the device. A.3.3.4 Diagnostic reference levels (DRLs) and achievable doses (ADs) Doses for dental radiographic procedures can vary widely between equipment and facilities (Both for a given technology and level of image quality selected), especially for panoramic and CBCT equipmentFootnote 1,Footnote 33. An effective approach to help minimize this variation and optimize patient dose is the establishment and use of Diagnostic Reference Levels (DRLs)Footnote 34. DRLs provide guidance to manage doses, attempting to ensure that equipment settings and the resulting dose is appropriate for the diagnostic objective DRLs are typically based on the 75th percentile of dose index distributions established from surveys of imaging practice for commonly performed examination types, each of which may also list clinical indications for which the examination is prescribed. DRLs attempt to summarize what would be considered reasonable application of a measured quantity of ionizing radiation. They can be an effective measure in reducing patient exposures for frequently used examination protocols, while allowing sufficient latitude to manage clinical needs and maintain diagnostic image quality for the clinical purpose intended. They are not regulatory or punitive limits, and can be exceeded where there is clinical need, but they provide thresholds to indicate a rationale should be provided when that practice level is exceeded. The need for a rationale is even stronger when a median dose of a particular examination/device consistently exceeds the DRL. DRLs may be established at the national (country), regional (multi-national), and local (single large facility or group of facilities in a geographic area) levels. Similarly, Achievable Doses (ADs) represent the median value (50th percentile) of the dose index distribution used to set the DRL value and can represent a second target for further dose optimization activities. DRLs for specific patient groups such as adults and children, and of different sizes where applicable for the imaging device (e.g. CBCT with different jaw size settings available), should be established. While this Safety Code recommends representative DRLs and ADs, a facility can set their own local values if enough data are available. The facility should create a list of reference doses for their examination protocols for each dental device and use these values within their quality assurance program. DRLs and ADs should be reviewed at least annually to assess their appropriateness. Determination of DRLs and optimization of doses must be assessed during the annual Quality Assurance testing (refer to Section C.3.3) by the service provider through which the device was purchased, or by an expert in radiation protection. Facilities which fall under provincial or territorial jurisdiction should contact the responsible regulatory authority in their respective region for information on any provincial or territorial statutory or regulatory requirements concerning dose limits. A listing of these responsible agencies is provided in Appendix I. Table 1 presents representative DRLs and ADs for dental X-ray procedures performed on an average adult patient, including the appropriate dosimetric indicator to use when measuring the dose for each procedure and the relevant conditions of measurement. Note that the values apply to equipment using both film and digital image receptors. These DRL and AD values are as referenced in the National Council on Radiation Protection and Measurements Report No. 172Footnote 35. It should be noted that the DRLs in Table 1 are based on the NCRP survey data from 2012 (U.S. and European data only; no Canadian data available), and as future technological advances cannot be predicted, it is possible that the appropriate values for the DRLs and ADs could change (i.e. lower) over time.
While DRLs (or ADs) serve as an indication of when optimization of radiation doses should be assessed, simply meeting a DRL does not necessarily mean that patient doses have been fully optimized. If the median dose indicator is found to be consistently below the suggested DRL, reasonable efforts to further minimize patient doses are still beneficial and should be pursued in order to attain a dose level that is ALARA while still maintaining sufficient diagnostic image quality for the purpose intended. It may be possible to acquire images of sufficient clinical image quality at doses well below any published DRL or AD values. Dental DRL values are recommended from distributions of the dose indices air kerma (Kair, mGy) and/or air kerma area product (KAP, mGy∙cm2). DRLs are based on typical/routine examinations using the standard techniques and loading factors at the facility. Since the same standard exposure settings are used for the majority of dental examinations, a measurement of output with the appropriate settings can be considered as the median incident air kerma for each dental examination protocol on a particular imaging device, or measurements from individual patient exams can be used to establish the DRLs. Separate measurements should be made for exposure settings for adult and child, and for different sizes where applicable for the imaging deviceFootnote 34. Section B: Facility and equipment requirementsB.1.0 Facility requirementsB.1.1 General criteriaIn the planning of any dental facility it must be ensured that persons in the vicinity of the facility are not exposed to levels of radiation which surpass the current exposure limits. Appropriate steps must be taken to ensure the following requirements are met:
Appendix II provides a detailed description of recommended dose limits. However, facilities under provincial/territorial jurisdiction may have different limits. While these dose limits establish the maximum exposure levels, in keeping with ALARA facilities can be designed to a lower shielding goal that reduces the exposure of dental workers in controlled areas and individuals in uncontrolled areas to levels below these limits (See Section B.1.2.3). For dental facilities, controlled areas are typically in the immediate areas where the X-ray equipment is used. The workers in these areas are primarily X-ray equipment operators who are trained in the proper use of the equipment and in radiation protection. Uncontrolled areas are those occupied by individuals such as patients (e.g. waiting areas), visitors to the facility, and employees who do not work routinely with or around radiation sourcesFootnote 36. In general, radiation levels directly beside dental X-ray equipment are such that the above limits could be exceeded, depending on the design of the equipment, the techniques used and the total workload. However, reduction in radiation intensity can be accomplished with the presence of a suitable shielding barrier between the patient and the operator, a suitable distance from the sources of radiation, or a combination of these, and restriction of persons from all areas in which the respective recommended dose limit could be exceeded. B.1.2 Design and plan of dental facilityThe owner is responsible for the radiation safety of the facility, including ensuring plans meet any requirements set forth by the applicable regulatory authority. In the early stages of designing and planning a dental facility, three steps should be taken to ensure the following requirements are met:
B.1.2.1 Preparation of facility plan In order to determine the shielding requirements for a radiographic facility a floor plan must be prepared, clearly identifying the following components:
B.1.2.2 Considerations for room design and layout When designing the layout of the X-ray facility, the following general recommendations must be considered.
B.1.2.3 Determination of parameters governing structural shielding requirements The thickness of the shielding material, such as lead, concrete, or gypsum wallboard, required to reduce radiation levels to the recommended dose limits or lower can be determined through calculations. In general, the radiation exposure to individuals depends primarily on the amount of radiation produced by the source, the distance between the exposed person and the source of the radiation, the amount of time that an individual spends in the irradiated area, and the amount of protective shielding between the individual and the radiation source. For all types of dental X-ray equipment, an expert in radiation protection must be consulted to ensure that the level of radiation safety of the facility is adequate. Given that dental radiography is performed at relatively low doses, dental facilities where the radiological workload is low may not need shielding in addition to the level of protection provided by typical gypsum wallboard construction. Special consideration must be given to radiation protection when using CBCT, transportable or mobile dental X-ray equipment. The parameters listed below must be considered for the calculation of barrier thicknesses. Allowance should be made for possible future changes in any one or all of these parameters, including increases in use and occupancy factors, in operating tube voltage and workload, as well as modifications in techniques that may require ancillary equipment. 1. The Maximum X-ray Workload (W) The workload is a measure of the operational time or the amount of use of the X-ray equipment. The workload can be determined by recording the current-time product of each irradiation taken for each dental X-ray device over a set period of time (i.e., week). If actual workload values are not available, estimated total workloads for various dental X-ray equipment are available in referencesFootnote 17. 2. The Occupancy Factor (T) The occupancy factor is the fraction of time that the area under consideration is occupied by the individual (employee or public) who spends the most time at that location while the X-ray equipment is operating. If occupancy factors cannot be readily estimated, typical factors are available from referencesFootnote 17. 3. The Use Factor (U) The use factor is the fraction of the workload during which the X-ray beam is pointed in the direction under consideration. If use factors cannot be readily estimated, typical factors are available from referencesFootnote 37. 4. Shielding Design Goal (P) The shielding design goal is the air kerma value used in shielding calculations to ensure that exposure levels for persons in controlled and uncontrolled areas are lower than or meet exposure limits. The shielding design goals for facilities with dental X-ray equipment should be one of the following in controlled areas:
The shielding design goal for uncontrolled areas should be 1 mGy/y. Provinces and territories may have specific requirements for shielding design goals. Facilities that fall under provincial or territorial jurisdiction should consult the regulatory authority listed in Appendix I for their respective region to obtain detailed information on any provincial or territorial statutory or regulatory requirements. B.1.3 Shielding calculationsIn dental facilities, shielding calculations must be made for both primary and secondary protective barriers. Primary protective barriers provide shielding from the direct X-ray beam and therefore must be placed in such an orientation as to intersect the X-ray beam. Secondary protective barriers are required to provide shielding from scattered and leakage X-rays. Comprehensive shielding calculations for dental facilities should only be performed by individuals with current expertise in structural shielding design and the acceptable methods of performing these calculations. It is recommended that shielding calculations be performed using the methodology presented in the National Council on Radiation Protection Measurements Report No. 145: Radiation Protection in DentistryFootnote 37. Note that shielding values should always be calculated, rather than using the values listed in the table in appendix F of NCRP Report No. 145. While NCRP Report No. 177 was published in 2019 and supersedes NCRP Report No. 145, this Safety Code recommends the shielding calculations methodology of NCRP Report No. 145 be used as it includes primary shielding considerations for intra-oral dental X-ray devices which will offer more comprehensive protection. The information outlined in Section B.1.2 along with the final plans of the installation must be submitted to the appropriate responsible government regulatory authority for review as required. Radiological facilities that fall under provincial or territorial jurisdiction should contact the responsible regulatory authority in their respective province or territory listed in Appendix I. B.1.3.1 Shielding of radiographic films and CR cassettes Film storage containers must be adequately shielded to ensure that excessive exposure of film by X-rays does not occur. Sufficient film shielding as needed must be in place to reduce the radiation level to stored film to less than 1.75 µGy over the storage period of the film. Once films are loaded into cassettes, radiation exposure levels should be less than 0.5 µGy and the resulting increase in the base-plus-fog should be less than 0.05 O.D. Given that CR Cassettes are used more frequently and therefore stored for shorter periods of time, the limit of 0.5 μGy is also considered to provide sufficient shielding for CR cassettes. B.1.3.2 Intra-oral dental X-ray equipment Primary and secondary shielding must be addressed for intra-oral dental X-ray equipment for which the X-ray tube can be manipulated in several directions. The walls where the X-ray tube can be directed are considered primary barriers, whereas the other walls, ceiling, and usually the floor are secondary barriers. If the patient is fully reclined and the X-ray tube is directed to the floor, then the floor becomes a primary barrier. If there is more than one dental chair in the room, shielding considerations must take into account the protection of patients and personnel from dental X-ray equipment used at both of the dental chairs. Shielding calculations are not generally performed for hand-held dental X-ray equipment operated in a temporary location. Consequently, strict adherence to other protective measures, including a distance of at least 2m between the hand-held X-ray device and all persons other than the operator and patient, is necessary to avoid unintentional radiation exposure to personnel and the public. To ensure appropriate radiation protection, a controlled area where imaging is conducted must be established and access restricted. B.1.3.3 Extra-oral dental X-ray equipment Extra-oral dental X-ray equipment generally has primary shielding behind the image receptor, meaning facility shielding only needs to address the secondary radiation. Due to differences in radiation output, the shielding requirements of panoramic and CBCT dental X-ray equipment cannot be assumed to be equivalent, and should be treated separately. B.2.0 Dental X-ray equipment requirementsB.2.1 Regulatory requirements for dental X-ray equipmentAll new, used and refurbished dental X-ray equipment, and accessories for such equipment, which are sold, imported or distributed in Canada, must conform to the requirements of the Radiation Emitting Devices Act and the Food and Drugs Act and their promulgated regulations, which are the Radiation Emitting Devices Regulations and the Medical Devices Regulations. The Radiation Emitting Devices Regulations, Schedule II, Part II - Dental X-ray Equipment38 sets out the requirements for information and labelling, construction and performance of dental X-ray equipment, with respect to radiation safety. The Medical Devices Regulations set out requirements for device safety, quality and effectiveness including device licensing. It is the responsibility of manufacturers, distributors and importers to ensure that their equipment complies with these regulations prior to importation and/or sale in Canada. Regulatory requirements should be reviewed during acceptance testing to ensure all device radiation safety, quality and effectiveness requirements are met. Dental facilities under provincial or territorial jurisdiction may be subject to additional requirements specified under their statutes and regulations. The Radiation Emitting Devices Act, the Food and Drugs Act and their promulgated regulations are available on the Government of Canada Justice Laws websiteFootnote 39. B.2.2 Equipment purchasingWhen purchasing dental X-ray equipment, a needs analysis should be performed to identify the appropriate type and specifications of equipment required to meet the clinical X-ray imaging needs. The following points should be considered: the types of investigations that the facility intends to perform with the equipment, the level of performance needed from the equipment, whether the dental staff of the facility possesses the expertise to use the equipment, whether adequate space is available for installation of the new equipment, the electrical capabilities of the facility with respect to equipment requirements, and the date on which equipment must be installed and operational at the facility. The need for additional equipment should be determined in advance and these items should be purchased at the same time as the X-ray equipment. This may include patient protective equipment (such as thyroid shields), personnel monitoring equipment (such as personal dosimeters), and testing equipment required to perform daily and monthly quality control procedures (such as specific test tools or phantoms). B.2.3 Acceptance testingAcceptance testing must be performed prior to any clinical use of the X-ray equipment. Acceptance testing is a process to verify compliance with the performance specifications of the X-ray equipment and that the equipment performance complies with federal and provincial or territorial regulations. For clarification regarding regulatory requirements, contact the applicable regulatory authority listed in Appendix I. The results from the acceptance testing should be used to set baseline values and acceptance limits on operational performance of the X-ray equipment. It is recommended that acceptance testing be performed by an expert with in-depth knowledge of the X-ray equipment, relevant regulations and radiation protection principles. The owner may consider having the acceptance testing performed by a person or organization who is independent of the manufacturer. A detailed description of the acceptance testing is provided in Section C.2.0. B.2.4 Existing dental X-ray equipmentIt should be noted that under the Radiation Emitting Devices Act the definition of a radiation emitting device includes "any component of or accessory to a device" that is capable of producing and emitting radiation. Replacements for any component or subassembly of dental X-ray equipment for which a construction or performance standard has been specified in the regulations must comply with the standard. In addition, upgraded components and/or software must be licensed by Health Canada. For replacement components, as well as resale of dental X-ray equipment, devices and components that are manufactured after May 15, 2018 are subject to the current dental X-ray equipment standard of the Radiation Emitting Devices Regulations. Devices and components manufactured prior to May 15, 2018 are subject to the standard as it read immediately before that date. Current and previous versions of the Radiation Emitting Devices Regulations are available on the Government of Canada Justice Laws website. Information on licensing of dental X-ray equipment, accessories or software is available from the Medical Devices Directorate of Health Canada (contact information available in Appendix I). The owner of a dental facility must ensure that any upgrades or changes to the equipment or software meet all applicable federal, provincial and territorial requirements. For clarification regarding regulatory requirements, contact the applicable regulatory authority listed in Appendix I. Any changes or upgrades of equipment affecting image quality and/or radiation dose must undergo acceptance testing. B.2.5 Retrofitting with digital imaging systemsWhen retrofitting a digital image receptor (e.g. Digital Radiography (DR) or Computed Radiography (CR) system) into a new or existing dental X-ray system, the owner of the facility must ensure that the digital image receptor meets the requirements of the Radiation Emitting Devices Act and Regulations, as well as the Food and Drugs Act and the Medical Devices Regulations. The system must be calibrated to reflect the sensitivity of the digital image receptor, and the system must be capable of sufficiently short exposure time settings for optimized exposure of the digital image receptor. For intra-oral dental X-ray equipment, all anatomical presettings must be adjusted to optimize for the digital image receptor, in order to minimize patient dose. The adjustments should be done by the vendor or dental service provider through which the device was purchased, or by an expert in radiation protection. B.3.0 Imaging processing systemsImage processing includes both film and digital processing of radiological images. Film processing systems have been extensively used in the past. Recently, with advances in digital technology, digital image processing systems are being used in many dental facilities. No matter the type of system used, optimization of image quality at an acceptable dose to the patient is a priority for dental facilities. This is achieved by ensuring image processing is an integral component of the facility's quality assurance program. B.3.1 Film based systemsThe ability to produce a radiograph of satisfactory diagnostic quality at an acceptable dose to the patient depends on the technique used when performing the examination, the appropriate selection of loading factors, the film-screen employed, the handling and processing of the film, and on the conditions of viewing the image. Good image quality requires proper darkroom techniques, routine processor quality control monitoring, and careful adherence to film and processor manufacturers' instructions. B.3.1.1 X-ray film X-ray films are sensitive to light, heat, humidity, chemical contamination, mechanical stress and X-radiation. Unexposed film must be stored in such a manner that it is protected from stray radiation, chemical fumes and light. Generally, X-ray films should be stored on edge, in an area away from chemical fumes, at temperatures in the range of 10°C to 21°C and humidity between 30% and 60%. The film manufacturers' instructions must be followed. Sealed film packages must be allowed to reach room temperature before opening to prevent condensation on the films. Radiation exposures to stored film must be limited to 1.75 µGy for the entire storage period of the film. Loaded cassettes must be stored in an area shielded from exposure to radiation; this area is usually in or near the X-ray room. Films should never be left inside cassettes with screens for any extended period of time. For panoramic dental X-ray equipment, the location of loaded and unexposed cassettes must be clearly marked. X-ray film past its expiry date should be discarded. B.3.1.2 Cassette and screen Facilities operating panoramic or cephalometric X-ray equipment may use film cassettes with screens as part of the image receptor. Cassettes or screens in poor condition will impair diagnostic quality. Problems are caused by dirty or damaged screens, warped cassettes, fatigue of foam, compression material or closure mechanism, light leaks, and poor film-screen contact. Cassettes should be checked regularly for wear and cleanliness and any damaged cassettes should be replaced. Manufacturers' recommended screen cleaner should be used. To avoid artifacts caused by dirt and dust, the intensifying screens and cassettes should be cleaned at least monthly. B.3.1.3 Darkroom Manual processing of films requires the use of a proper, well-equipped darkroom. Automatic film processors also require properly designed darkrooms, with the exception of daylight loaders on automatic image processors. While specific details may vary from installation to installation, all darkrooms must include the following basic features:
B.3.1.4 Cleanliness Cleanliness in the darkroom and of the screens and cassettes is essential. It is important to maintain the cleanest environment possible in order to minimize any artifacts caused by dirt, dust, or improper handling of film.
B.3.1.5 Handling of film
B.3.1.6 Film processing Improper or careless processing of exposed radiographic films can cause films of poor diagnostic quality and consequently result in an increased chance of a wrong diagnosis or the need for repeat exposures. With both manual and automatic processing, to achieve full development of a film which has been exposed using correct radiographic technique factors, the film must be processed in chemically fresh developer, at proper temperature and for sufficient time to ensure that the silver in exposed silver halide crystals in the film emulsion is completely reduced into black metallic silver. If this is not done, the blackening of the film will not be optimal and the tendency will be to increase radiation exposure to achieve proper image density. Other factors can also affect the quality of the processed film. These include cleanliness of the processing system, film immersion time, and agitation. To ensure proper processing of films certain basic recommendations must be considered:
B.3.1.7 Viewbox The conditions of viewboxes must be checked regularly along with the conditions under which dentists and other health care professionals examine radiographs since this may influence diagnostic accuracy. Problems with improper illumination due to the non-uniformity of fluorescent tubes or degradation and discolouration of the viewing surface must be corrected. It is best to use only one type of fluorescent tube within a facility. These tubes should be changed when signs of aging develop, such as flickering, inconsistent illumination or low light output. Care should be taken to clean the viewing surface of the viewbox such that no dirt could influence diagnostic accuracy. B.3.2 Digital imaging systemsMany Canadian dental facilities have transitioned from film-screen imaging to digital imaging. Various digital systems are available using different types of image receptor technologies to produce the digital images. In general, digital imaging equipment is categorized into two groups: Computed Radiography (CR) systems or Digital Radiography (DR) systems.
Quality control testing of digital image systems is essential. Verification of proper functionality of the X-ray imaging equipment along with appropriate selection of technique and loading factors remains essential for obtaining a satisfactory image at a minimal dose to the patient. For digital systems, specific quality control testing must also be performed on the image acquisition, storage, communication and display systems. In Section C of this Safety Code, general quality control tests have been included for digital imaging systems. In addition to these tests, all equipment-specific, manufacturer-specified tests must also be performed. B.3.2.1 Computed radiography imaging plates Computed radiography imaging plates are reusable and can be exposed, read and erased repeatedly. For this reason, it is necessary to evaluate the conditions of imaging plates on a regular basis. With normal use, the accumulation of dust, dirt, scratches and cracks may reduce image quality. Exposure to chemical agents, such as non-approved imaging plate cleaners, handling with dirty or wet hands or contact with hand lotions are all possible causes of imaging plate damage. A log book should be maintained to track the physical conditions of all imaging plates and cassette assemblies. The cleaning frequency depends on patient volume, plate handling, and the frequency at which artifacts are perceived. When significant artifacts are visible in the image, plates need to be discarded. Significant artifacts detrimentally impact the diagnostic quality of the image and may lead to unnecessary retakes. In general, a weekly visual inspection for dust and dirt is recommended. The imaging plates must be cleaned monthly following manufacturer recommended procedures and using manufacturer recommended cleaners. Cleaner must not be poured directly onto the plates as this may cause staining. B.3.2.2 CR cassette Under normal conditions of use, dust and dirt can accumulate on cassettes. A log book should be maintained to track the physical conditions of all cassettes. In general, a weekly visual inspection for dust and dirt should be done. Monthly cleaning of CR cassettes following manufacturer recommended procedures and using manufacturer recommended cleaners must be done (See Section C.3.2, item M1). When not in use, CR cassettes, loaded with an imaging plate, must be stored in a closed container that blocks out ambient light and such that the level of radiation exposures is limited to 0.5 µGy for the storage period. B.3.2.3 Intra-oral CR and DR image receptors Intra-oral image receptors must be cleaned and disinfected after each patient use. Manufacturer recommended cleaners and cleaning procedures should be used. Also note that, while beyond the scope of this Safety Code, regulatory authorities may have infection prevention and control requirements applicable to disinfecting image receptors. Intra-oral CR and DR image receptors may deteriorate over time due to extensive handling and positioning within the mouth, therefore these receptors must be regularly inspected for damage, including wear, warping, dents and cracks that may result in image artifacts. When significant artifacts are visible in the image, receptors need to be discarded. Significant artifacts detrimentally impact the diagnostic quality of the image and may lead to unnecessary retakes. The cable on DR image receptors must also be checked regularly for damage (e.g. fraying) that may prevent acquisition of the image data. If a cord is damaged, the receptor must not be used until the damaged cords are replaced. Damaged cords may lead to unnecessary retakes due to failure of the image receptor. B.3.2.4 Electronic display devices The performance of electronic display devices must be checked routinely. Monthly verification of the display must be performed using test patterns designed for evaluating various characteristics of display performanceFootnote 40,Footnote 41 (See Section C.3.2, item M7). A detailed annual evaluation should be performed by a expert with knowledge in electronic display device testing. The cleanliness of the display surface must be maintained and basic functionality should be confirmed (power on/off, visible display). Manufacturer recommended cleaners and cleaning procedures must be followed. Section C.3.3, item A16 of this document provides a description of these quality control tests. Attention must be given to reading room viewing conditions when performing quality control tests of display monitors. B.3.2.5 Imaging software There are many options for image processing available across various imaging software, ranging from standard image enhancement options (e.g. window and levelling, edge enhancement), to implant planning software for CBCT equipment as well as the possibility of adding a management system that can maintain an exposure registry for repeat analysis. The capabilities of the imaging software used to display dental radiographs must suitably address the specific clinical needs of the facility. Image processing software should also ensure preservation of the original image data, such that after image processing options have been applied the unprocessed image can still be viewed. The imaging software should not allow diagnostically inadequate images to be immediately deleted, so that reject/retake analysis of the inadequate image can be done during quality control. B.3.2.6 Image archiving system In digital imaging, a system must be in place to manage patient images so that secure storage and timely retrieval of images is possible. Attention must be given to ensure that the quality of patient images is maintained (i.e. uncompressed, original image data) and that patient information is not lost or unintentionally altered. Such situations can lead to repeat radiographic examinations and misdiagnoses for patients. When deciding upon specifications of an image archiving system, the following key components should be considered:
B.3.2.7 Teleradiology Teleradiology is the electronic transmission of radiological images from one location to another for the purposes of interpretation and/or consultation. Through teleradiology, digital images and patient information can be accessed electronically from multiple sites simultaneously. The benefits of teleradiology include more efficient delivery of patient care and the ability to provide radiological services to facilities in remote areas which do not have image interpretation capabilities available on-site. Security of patient information must be a priority. Only authorized individuals must be able to access patient data and images. Authorized system users must understand the importance of keeping system passwords confidential. Since teleradiology involves the acquisition and interpretation of patient images at different sites, it is important that policies and procedures be in place at all locations to ensure image quality is optimized and comparable among all facilities accessing patient images. This is especially important when official authenticated written interpretations are made through teleradiology. Images sent by teleradiology must not be digitally compressed, as this will reduce the image quality. Images obtained through post processing of the original image must not be used to the exclusion of the original images themselves, as they must only be used to support the interpretation process. The relevant workstation quality control tests set out in Section C must be performed at the required frequencies for workstations used for interpretation of teleradiology images. B.4.0 Other equipmentConsideration must be given to other equipment, such as those used for personnel and patient protection, and equipment testing, which are necessary for ensuring the radiation safety of a dental facility. Protective equipment must provide adequate protection without being unduly restrictive and heavy. All test equipment must be properly maintained and carefully stored. B.4.1 Protective Equipment
B.4.2 Test equipment
B.5.0 Radiation protection surveysA radiation protection survey is an evaluation of the radiation safety of a dental facility. The survey is intended to ensure compliance with the requirements of this Safety Code, to demonstrate that X-ray and auxiliary equipment function properly and according to applicable standards, and that the equipment is installed and used in a way which provides maximum radiation safety for operators, patients and others. As part of the radiation safety program for a facility, it is the responsibility of the owner to ensure that radiation protection surveys are conducted as indicated in Section B.5.1 below. Facilities under provincial or territorial jurisdiction may be subject to requirements under their statutes. The authorities listed in Appendix I should be contacted for details of the regulatory requirements of individual provinces and territories. The regulatory authority may request reports of quality control performed at the facility during the investigation or once it has been completed. Safety measures such as protective equipment and shielding are also examined to ensure that they are present and provide the required protection. It is important, therefore, that X-ray facilities are surveyed at regular intervals. B.5.1 General proceduresRoutine operation of any new installation or an installation which has undergone modifications should be deferred until a complete survey has been made by an expert in radiation protection. These procedures include evaluation of the facility design to ensure adequate shielding is in place, inspection and evaluation of the performance of X-ray equipment and accessories, and evaluation and recommendation of radiation protection programs. The owner of the facility (or another delegated staff member) must contact the appropriate regulatory authority to ascertain inspection and acceptance testing procedures in that jurisdiction. Some jurisdictions may require that the facility be declared in compliance with applicable governmental regulations prior to operations. Provincial and territorial regulations and professional orders may also establish requirements relating to who can perform specific actions or roles outlined in this Safety Code, including some in this section. For clarification regarding regulatory requirements, contact the applicable regulatory authority listed in Appendix I. For a new facility, it is particularly advantageous to perform visual inspections during the construction phase, to ensure compliance with design specifications and to identify faulty material or workmanship, since deficiencies can be remedied more economically at this stage than later. Such inspections should include determination of lead and/or concrete thickness and density, and degree of overlap between lead sheets or between lead and other barriers. Evidence/documentation of installation of the shielding should be retained as part of the facility's shielding records. For existing installations, a survey must be carried out after any changes are made which might produce a radiation hazard. This includes alteration of protective barriers, equipment modification and replacement, change in location or orientation of an X-ray device, structural changes to the room, changes in operating procedures, or increased workloads. Finally, radiation protection surveys must be carried out at regularly scheduled intervals during routine operations to detect problems due to equipment failure or any long-term trends toward a decrease in the level of radiation safety. Facilities shouldntact the applicable regulatory authority to establish the survey schedule. If a survey frequency is not set by the responsible regulatory authority, surveys may be conducted every three years. For clarification regarding regulatory requirements, contact the applicable regulatory authority listed in Appendix I. The results of such surveys, including conclusions drawn by the expert in radiation protection, must be submitted to the owner in a written report. All such reports must be retained by the owner. For federal facilities, radiation survey reports must be maintained for 5 years and personnel dosimetry records for the lifetime of the facility. B.5.2 Survey reportThe survey report must present, in a clear systematic way, the details and results of the measurements carried out, as well as the conclusions drawn and recommendations made by the surveyor. Any unusual findings about the equipment itself, the facility or operating procedures, which could affect the safety of operators or other persons in the vicinity of the X-ray facility, must be clearly identified. The survey report must include the following:
B.6.0 Disposal of dental X-ray equipmentWhen X-ray equipment is considered for disposal, an assessment should be made as to whether the equipment can be refurbished and/or recycled. Communication with the manufacturer or supplier of the equipment should be made as to whether the equipment or components of the equipment can be recycled or returned. Once the decision has been made to dispose of X-ray equipment, an assessment must be made to determine if any equipment components contain hazardous materials. An assessment should include the following:
It is strongly recommended that disposal of X-ray equipment be delegated to an X-ray service provider that specializes in the disposal of such systems. Safe work practices during disposal must be used so that workers are not exposed to hazards. The following disposal actions are recommended:
It is recommended that dental facilities under provincial or territorial jurisdiction contact the responsible regulatory authority in their respective province or territory for further information. A listing of these responsible regulatory authorities is provided in Appendix I. Section C: Quality assurance programC.1.0 IntroductionAll dental facilities must develop and maintain an effective quality assurance program. In dental radiography, a quality assurance program is defined as the planned and organised actions necessary to provide adequate confidence that dental X-ray equipment and related components reliably produce quality radiographs with minimum doses to patients and staff. A Quality Assurance program includes quality control procedures for the monitoring and testing of dental X-ray equipment and related components, and administrative procedures to ensure that monitoring, evaluation and corrective actions are properly performed. The owner of a dental facility has the responsibility of establishing a quality assurance program that examines all practices of the facility which affect:
C.1.1 Goals of the quality assurance programThe ultimate goal of a quality assurance program is to ensure accurate and timely diagnosis at the minimum dose to the patient and staff. In order to have a successful quality assurance program it is essential that equipment is in proper working condition and all staff members understand the goals of the program and are committed to the implementation of the program through full participation. Any program initiated only to comply with regulatory requirements is not likely to provide maximum possible benefit to the patient. It is, therefore, essential that all dental staff understand, support and participate in the operation of the quality assurance program. Some provincial/territorial jurisdictions require facilities to implement and participate in a quality assurance program. For clarification regarding regulatory requirements, contact the applicable regulatory authority listed in Appendix I. Information obtained from dental X-ray equipment must be of highest quality to ensure accurate diagnosis and treatment. If critical elements are missing or image artifacts are present, the image is considered to be of poor quality. The consequence of poor quality diagnostic information may be incorrect diagnosis resulting in repeat X-ray procedures, unnecessary radiation doses to the patient and operator, delayed or improper patient treatment and increased cost. C.1.2. Implementation of quality assurance programThe implementation of a quality assurance program need not be complicated. It consists of establishing quality control procedures for the equipment along with an administrative methodology to ensure that monitoring, evaluation and corrective actions are properly performed. C.1.2.1 Establishment of quality control procedures The following four steps must be included for the establishment of quality control procedures:
Many dental X-ray equipment supply companies distribute quality assurance kits which include test equipment to perform quality control tests and record keeping forms. Such kits may be useful in setting up quality assurance programs. C.1.2.2 Establishment of administrative procedures The following administrative procedures must be included in the establishment of an effective quality assurance program:
C.2.0 Acceptance testingAcceptance testing is a process to verify compliance with the performance specifications of the X-ray equipment and that the equipment performance complies with federal and provincial or territorial regulations. Acceptance testing must be performed prior to any clinical use of the equipment. It is recommended that acceptance testing be performed by an expert with in-depth knowledge of the X-ray equipment, relevant regulations and radiation protection principles. The owner may want the acceptance test to be performed by a person or organization who is independent of the manufacturer. Acceptance testing of a dental X-ray system includes several major steps:
Regulatory requirements should be reviewed during acceptance testing to ensure all requirements for device radiation safety, quality and effectiveness are met (See Section B.2.1). The results from the acceptance testing should be used to set baseline values and acceptance limits on operational performance of the X-ray equipment. These baseline values and limits are essential to the quality assurance program. C.2.1 Acceptance testing evaluationAcceptance testing for dental X-ray equipment should evaluate at least the items listed in Table 2. Not all equipment will be subject to the full set of tests. The type of equipment and its configuration will dictate the sets of tests to be performed. More detailed information on acceptance testing on dental X-ray equipment, including specifications for phantoms, is available from the International Electrotechnical Commission (IEC) for traditional devicesFootnote 46 and cone beam CTFootnote 47, as well as the European CommissionFootnote 8,Footnote 16. Appropriate loading factors that optimize the radiation dose while maintaining sufficient diagnostic image quality must be established for all imaging techniques used. For techniques that are set manually, a techniques chart must be affixed on or near the control panel. The loading factors for all preset techniques, where the techniques are selectable by anatomical indications (e.g. for "adult" and "bitewing"), must be optimized based on the results of acceptance testing, with the presets on the devices adjusted as required. It should not be assumed that the manufacturer recommended settings for preset techniques will provide optimized radiation doses for a given specific installation of a dental X-ray device.
CR: Computed Radiography, DR: Digital Radiography, CBCT: Cone Beam Computed Tomography C.3.0 Quality control testing procedures and equipmentQuality control testing must be carried out during routine operation of a dental facility. This section sets out the required and recommended quality control tests, the associated test equipment and testing frequencies. More detailed information on quality control testing on dental X-ray equipment, including specifications for phantoms, is available from the International Electrotechnical Commission (IEC) for traditional devicesFootnote 46 and cone beam CTFootnote 47, as well as the European CommissionFootnote 8,Footnote 16. Quality control testing of a dental X-ray system includes several major steps:
Test equipment required for these tests must be readily available to the individuals responsible for performing these tests. All test equipment must be calibrated and verified to be operating accurately according to the frequency determined by manufacturer. Individuals performing quality control tests must be trained in the proper operation of the test equipment and in performing the tests. In the following sections, the descriptions of each test indicate whether performance of the test is required or recommended. In addition, not all equipment will be subject to the full set of tests listed in the following sections. The type of imaging system, whether film-based, CR, or DR, to which the quality control tests apply, is identified. Alternative tests can be performed in place of those specified if it can be shown that the test is capable of verifying the necessary parameter or performance. The quality control tests and frequencies indicated in this safety code are for general application to all dental X-ray equipment. However, any additional quality control tests or requirements for more frequent testing as indicated by the manufacturer for a specific dental X-ray device should be followed. C.3.1 Daily quality control testingDaily quality control tests are listed in Table 3. The X-ray systems to which the tests are applicable, and the test numbers corresponding to the descriptions following the table are provided. These tests must be performed at the beginning of each day that dental radiography is conducted before commencing patient examinations and processing any patient images. These tests should be able to be performed by dental X-ray equipment operators.
CR: Computed Radiography, DR: Digital Radiography, CBCT: Cone Beam Computed Tomography
The following quality control tests must also be performed:
Test equipment for the daily quality control testing is listed in Table 4.
FB: Film Based, CR: Computed Radiography, DR: Digital Radiography, IO: Intra-oral, PN: Panoramic, CP: Cephalometric, CBCT: Cone Beam Computed Tomography C.3.2 Monthly quality control testingMonthly quality control tests are listed in Table 5. The X-ray systems to which the tests are applicable, and the test numbers corresponding to the descriptions following the table are provided. These tests should be able to be performed by dental staff.
CR: Computed Radiography, DR: Digital Radiography, CBCT: Cone Beam Computed Tomography
Test equipment for the monthly quality control testing is listed in Table 6.
FB: Film Based, CR: Computed Radiography, DR: Digital Radiography, IO: Intra-oral, PN: Panoramic, CP: Cephalometric, CBCT: Cone Beam Computed Tomography C.3.3 Annual quality control testingAnnual quality control tests are listed in Table 7. The X-ray systems to which the tests are applicable, and the test numbers corresponding to the descriptions that follow the table are provided. These tests should be performed by the manufacturer or a service provider with appropriate expertise.
CR: Computed Radiography, DR: Digital Radiography, CBCT: Cone Beam Computed Tomography
|X1 - X2| ≤ 0.1 (X1 + X2) where X1 and X2 are average air kermas (exposures) per current time product. The values of X1 and X2 must be determined at (a) where the X-ray tube current is fixed, at each combination of two settings of the controlling timer, and (b) where the irradiation time is fixed, at each combination of two X-ray tube current settings (if the equipment uses a one-peak high voltage generator, the range of X-ray tube current time product must be limited to irradiation times not shorter than 80 ms).
The performance of the backup timer must be verified to ensure safe performance of the equipment. For extra-oral dental X-ray equipment, the current time product must not exceed 640 mAs or the product of X-ray tube voltage, X-ray tube current and irradiation time must not exceed 64 kJ. For intra-oral dental X-ray equipment, the current time product must not exceed 32 mAs or the product of X-ray tube voltage, X-ray tube current and irradiation time must not exceed 3.2 kJ.
Test equipment for the annual quality control testing is listed in Table 8.
FB: Film Based, CR: Computed Radiography, DR: Digital Radiography, IO: Intra-oral, PN: Panoramic, CP: Cephalometric, CBCT: Cone Beam Computed Tomography Appendix I: Federal/provincial/territorial regulatory authoritiesA listing of Federal/Provincial/Territorial Radiation Protection Committee members is available online. https://www.canada.ca/en/health-canada/services/environmental-workplace-health/radiation/federal-provincial-territorial-radiation-protection-committee.html Federal government Consumer and Clinical Radiation Protection Bureau, Health Canada Medical Devices Directorate, Health Canada Labour Program, Employment and Social Development Canada British Columbia Senior Manager, Risk Analysis Unit WorkSafeBC E-mail: or Website: http://worksafebc.com/en Alberta Specialized Professional Services Occupational Health & Safety Program Delivery Alberta Labour and Immigration E-mail: Website: https://www.alberta.ca/register-radiation-equipment.aspx Saskatchewan Radiation Safety Unit Ministry of Labour Relations and Workplace Safety E-mail: Website: https://www.saskatchewan.ca/business/safety-in-the-workplace/hazards-and-prevention/radiation Manitoba Radiation Protection Services Medical Physics Division CancerCare Manitoba E-mail: Website: https://www.cancercare.mb.ca/Research/medical-physics/radiation-protection-services Ontario (for issues related to patient and public safety) X-ray Inspection Service Ontario Ministry of Health E-mail: General Enquiries: ; Shielding applications: Website: http://www.health.gov.on.ca/en/ Ontario (for issues related to worker safety) Manager, Radiation Protection Service Occupational Health and Safety Branch Ministry of Labour, Training and Skills Development E-mail: Website: http://www.labour.gov.on.ca/ Quebec Direction du Génie biomedical, de la logistique et de l'approvisionnement (DGBLA) Ministère de la Santé et des Services sociaux (MSSS) E-mail: Website: https://www.msss.gouv.qc.ca/index.php New Brunswick WorkSafeNB Prevention Division Manager - Ergonomics & Occupational Hygiene E-mail: Website: https://www.worksafenb.ca/ Nova Scotia General Inquiries and Reporting Occupational Health and Safety Division Nova Scotia Department of Labour, Skills and Immigration Toll Free 1-800-952-2687 (24 Hrs) E-mail: Website: https://novascotia.ca/lae/healthandsafety/ Prince Edward Island Workers Compensation Board of PEI Occupational Health and Safety Division E-mail: Website: http://www.wcb.pe.ca Newfoundland and Labrador Department of Digital Government and Service NL Occupational Health and Safety Division E-mail: Website: https://www.gov.nl.ca/dgsnl/ohs/ Northwest Territories and Nunavut Occupational Health and Safety Government of the Northwest Territories E-mail: Website: https://my.hr.gov.nt.ca/health-safety Yukon Territory Occupational Health and Safety Yukon Workers' Compensation Health and Safety Board E-mail: Website: https://www.wcb.yk.ca/ Appendix II: Dose limits for occupational ionizing radiation exposuresFor the purpose of this Safety Code, individuals may be classified in one of two categories: (1) radiation workers, and (2) members of the public and persons who are not declared radiation workers. The dose limits are given for both categories in Table AII.1. These dose limits are based on the latest recommendations of the International Commission on Radiological Protection (ICRP) as specified in ICRP Publication 103Footnote 49 and 118Footnote 50. Dose limits for occupationally-exposed dental workers apply only to irradiation resulting directly from their occupation and do not include radiation exposure from other sources, such as medical diagnosis and background radiation.
Appendix III: Facility radiation protection checklist
Appendix IV: Radiation measurement unitsExposureFollowing the lead of the International Electrotechnical Commission, the air kerma (in gray, Gy) replaces the exposure (in roentgen, R) as the measure of exposure. The relationship between the two units is as follows:
Absorbed doseThe gray (Gy) replaces the rad (rad) as the unit of absorbed dose. The relationship between the two units is as follows:
Equivalent dose or effective doseThe sievert (Sv) replaces the rem (rem) as the unit of equivalent dose or effective dose. The relationship between the two units is as follows:
Note: m = milli = 10-3; µ = micro = 10-6 AcknowledgementsThis Safety Code reflects the work of many individuals. It was prepared and compiled by Richard Smith, Richard Tremblay and Jennifer Renaud of the Ionizing Radiation Physical Sciences Division, Consumer and Clinical Radiation Protection Bureau. The assistance of the members of the Ionizing Radiation Physical Sciences Division during the preparation of this Safety Code is acknowledged. Appreciation is expressed to following individuals, organizations, and agencies whose comments and suggestions helped in the preparation of this Safety Code:
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Hereditary Effects of Radiation. United Nations Scientific Committee on the Effects of Atomic Radiation, Report to the General Assembly, with Scientific Annex (United Nations, New York). Return to footnote 5 referrer Footnote 6UNSCEAR (2000). Sources and Effects of Ionizing Radiation. Volume I: Sources; Volume II: Effects. United Nations Scientific Committee on the Effects of Atomic Radiation, Report to the General Assembly with Scientific Annexes. (United Nations, New York). Return to footnote 6 referrer Footnote 7Siewerdsen J. H. Jaffray D. A., Cone‐beam computed tomography with a flat‐panel imager: Magnitude and effects of x‐ray scatter. Med Phys. 2001; 28: 220-31. Return to footnote 7 referrer Footnote 8EC (2012). European Commission. Radiation Protection No. 172: Cone Beam CT For Dental And Maxillofacial Radiology (European Commission, Brussels). Return to footnote 8 referrer Footnote 9Smith R, Tremblay R, Wardlaw GM. 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Evaluation and routine testing in medical imaging departments - Part 3.4: Acceptance tests - Imaging performance of dental X-ray equipment, 1st ed., IEC 61223-3.4 Return to footnote 46 referrer Footnote 47IEC (2021). International Electrotechnical Commission. Evaluation and routine testing in medical imaging departments - Acceptance testing and quality control of dental extra-oral X-ray equipment used with dental cone beam computed tomography, 1st ed., IEC 61223-3-7 Return to footnote 47 referrer Footnote 48Stam W, Pillay M. Inspection of lead aprons: a practical rejection model. Health Phys. 2008;95 Suppl 2:S133-6. Return to footnote 48 referrer Footnote 49ICRP (2007). International Commission on Radiological Protection. The 2007 Recommendations of the International Commission on Radiological Protections, ICRP Publication 103, Annals of the ICRP 37(2-4) (Elsevier Science, New York). Return to footnote 49 referrer Footnote 50ICRP (2012). International Commission on Radiological Protection. ICRP Statement on Tissue Reactions / Early and Late Effects of Radiation in Normal Tissues and Organs - Threshold Doses for Tissue Reactions in a Radiation Protection Context. ICRP Publication 118, Annals of the ICRP 41(1/2) Return to footnote 50 referrer |