Chapter 9 Human Use of Radiation Producing Equipment

Transcription

1 Chapter 9 Human Use of Radiation Producing Equipment 9.1 Acquisition and Registration of Radiation Producing Equipment The Radiation Safety Section (RSS) is responsible for maintaining the registration and for ensuring adherence to the regulations for the use of all equipment that produces ionizing radiation and must be kept informed about all plans to acquire, store, and dispose of radiation producing equipment. Acquisition includes purchases, transfers from other departments or institutions, gifts, loans, leases, etc. In addition, information must be provided regarding who is responsible for the use or storage of the equipment. The Purchasing Section assists the RSS by providing copies of all purchase requisitions for radiation producing machines. Purchase of machines for approved facilities will proceed normally. Purchase of machines for facilities that have not been approved may encounter significant delays, especially if the facility does not meet the standards for radiation levels in unrestricted areas. 9.2 General Requirements and Administrative Controls All personnel who administer x rays or other forms of ionizing radiation to humans are subject to the requirements outlined in this chapter. Most of these requirements are taken from the Illinois Radiation Protection Act and Sections 340, 360, 400, and 401 of the Illinois Emergency Management Agency (IEMA) regulations Personnel Permitted to Use Radiation Producing Machines in the Healing Arts Licensed Medical, Dental, and Podiatric Practitioners - Persons licensed to practice the treatment of human ailments by virtue of the Illinois Medical, Dental, or Podiatric Medical Practice Acts are permitted to intentionally administer radiation to human beings. Other Accredited Personnel - Accredited individuals may administer radiation to humans while under the supervision, prescription, or direction of a person licensed to practice under the Illinois Medical, Dental, or Podiatric Medical Practice Acts. The IEMA recognizes and accredits medical radiographers, nuclear medicine technologists, radiation therapy technologists, and chiropractic technologists in accordance with Section 401 of their regulations. UIC departments who employ accredited personnel must maintain clear legible copies of the current certificates of accreditation for all individuals who are required to be accredited. These copies must be maintained for all current employees and for all individuals employed within at least the last two years. Personnel Exempted From Accreditation - The following personnel are exempted from accreditation requirements: A student enrolled in a training program approved by IEMA applicable to his/her profession who, as a part of his or her course of study, may apply ionizing radiation to human beings while under the supervision of a practitioner licensed in Illinois; A person registered with IEMA as a student-in-training in limited diagnostic radiography may Page 1 of 19

2 apply ionizing radiation to humans while under the supervision of a licensed practitioner provided the procedure is listed in Appendix A of Part 401 of the IEMA regulations. A copy of Appendix A may be obtained from the RSS; A person employed as a dental assistant who performs dental radiography for a dentist licensed in Illinois; A technician, nurse, or other assistant who performs radiography under the supervision of a person licensed under the Illinois Podiatric Medical Practice Act; and A nurse, technician, or other assistant who, under the supervision of a person licensed under the Illinois Medical Practice Act, administers radiation to human beings, but only when such administration is performed on employees of a business at a medical facility owned and operated by that business Prohibited Uses of X-ray Equipment The following uses of x-rays and other machine produced ionizing radiations are strictly prohibited: Exposure of individuals for training, demonstration, or other non-healing arts purposes; Exposure of individuals for the purpose of healing arts screening (defined as the examination of human beings for the detection or evaluation of potential diseases when such examinations are not specifically ordered by a licensed practitioner of the healing arts legally authorized to prescribe such x-ray examinations for the purpose of diagnosis or treatment. However, healing arts screening does not include mammography or self-referred patients.); Use of fluoroscopy as a substitute for radiography or in lieu of proper anatomical positioning/centering procedures prior to radiographic studies; Use of fluoroscopic equipment with phosphorescent screens. Image intensification shall be utilized on all fluoroscopic equipment; Use of direct exposure x-ray film (without intensifying screens) for routine diagnostic radiological imaging procedures, other than intraoral dental radiography and therapeutic portal imaging; and Use of photofluorographic systems Personnel Monitoring (Dosimeters and TLD Rings) All personnel who are associated with the operation of any x-ray system are subject to the requirements outlined in Chapter 12 of this manual with regard to wearing Dosimeters and TLD rings. If an individual is likely to receive 10% or more of any exposure limit, that individual must be monitored for radiation exposure. In general, all operators of x-ray equipment and any ancillary personnel are required to wear dosimeters. Personnel whose hands are in close proximity to the beam of a fluoroscopy unit may also need to wear a TLD ring badge. An RSS Health Physicist can assist you in these matters. Page 2 of 19

3 Monthly monitoring reports are sent to a representative in each monitoring group for posting or circulation. These results are also kept on file in the RSS and an individual may review his or her monitoring results at any reasonable time Reduction of Unnecessary Patient Exposure Reduction of unnecessary patient exposure can be accomplished by proper utilization of three distinct processes; selection of the patient, performance of the examination, and interpretation of the radiological findings. The Bureau of Radiological Health in conjunction with the World Health Organization published excellent guidance regarding these matters in Chapter 9 of The Correlated Lecture Laboratory Series in Diagnostic Radiological Physics published in The entire text of this chapter is included in Appendix K. All medical personnel, physicists, and administrators involved with the administration of diagnostic x-ray examinations are strongly urged to read this information. 9.3 Training Requirements All individuals who operate x-ray equipment (including linacs and other medical radiation producing machines) for diagnostic or therapeutic purposes, including licensed practitioners, are required by the IEMA regulations to be provided with training. Training must include the following topics: A description of the health protection problems associated with exposure to radiation, the risks of radiation exposure to the embryo and fetus, and the precautions and procedures that should be taken to minimize exposure; A copy of the written operating and safety procedures for the equipment to be used must be provided, which includes the restrictions required for the safe operation of each radiation machine; The requirement that workers must satisfy all regulatory requirements that are within their control; The requirement that workers must to report any condition that may constitute, lead to, or cause a violation of regulatory requirements; Instruction in the proper use of personnel and patient protective devices; A review of the procedures that must be followed to minimize patient and personnel exposures and the procedures for selecting personnel to support patients or film during radiographs; The requirement that workers must properly use personnel monitoring devices that are supplied to them, and the availability of monitoring results; Film processing procedures; and Prohibited uses of x-ray machines. Page 3 of 19

4 Each individual who operates x-ray equipment for diagnostic or therapeutic purposes, excluding licensed practitioners, shall be provided with initial training before being allowed to use the equipment and annual in-service radiation safety training. Initial and annual in-service training must include all of the topics listed above. Training records must include the names of the instructors and attendees, the date and duration of instruction, and the topics covered. In addition, a signed statement must be obtained from each attendee indicating that they have received and understand the information presented. Training records for all personnel must be maintained by the project director for inspection purposes. Licensed practitioners should be provided with a copy of this Chapter, Chapter 12, Personnel Monitoring and External Dosimetry, and a copy of the operating and emergency instructions for the equipment that will be used before being granted permission to use x-ray equipment. A signed statement must be obtained indicating they have received and understood the above information. This statement must be maintained by the project director for inspection purposes. 9.4 General Equipment and Operation Requirements for Diagnostic X-ray Systems Beam Filtration - The raw output of an x- ray tube contains a significant amount of low energy x rays that do not contribute to the useful image of a radiograph, but cause the patient to receive a high radiation dose to the nearest surface. Since low energy x rays are more readily absorbed in shielding than higher energy x rays, a thin slab of aluminum is usually placed between the x- ray tube and the beam port. This increases the ratio of high energy x rays to low energy x rays, a process known as beam hardening. Figure 9.1, copied from the Radiological Health Handbook i, shows the effect of beam filtration on exposure for various kvp x rays. The x-ray tube glass also helps to harden the beam. An optimum amount of beam hardening is desired to remove a sufficient fraction of the harmful low-energy x rays, while leaving enough higher energy x rays to produce a high quality image in a short period of time (small fractions of a second). Short exposure times are needed to minimize blurring of the image due to movement of the patient. One method of determining the hardness of an x-ray beam is to determine how much additional aluminum is needed to reduce the output of the beam by a factor of two. This thickness is referred to as the half-value layer and is dependent on the energy spectrum of the x rays being produced in the tube and the types and amounts of shielding already present. The harder the beam, the thicker the half-value layer will be. Minimum half-value layers for different operating voltages are specified in the IDNS regulations. This is done to ensure sufficient beam hardness, Page 4 of 19

5 preventing unnecessary exposure of the patient to low energy x rays. Beam-On Indicators - The control panel of every x-ray machine must be equipped with a device (usually a milliammeter or labeled indicator lamp) that will give a positive indication of the production of x rays whenever the x-ray tube is energized. If two or more x-ray tubes are controlled by one exposure switch, the tube or tubes that have been selected must be clearly indicated on the control panel and at or near each selected x-ray tube. Mechanical Support of Tube Head - The tube housing assembly supports must keep the tube housing from moving while exposures are being taken except when the tube is designed to move during the procedure. For example, during a chest exposure, the tube assembly should not move; However, the tube housing should move during a tomography or CT procedure. Leakage Radiation From the Tube Housing - Except for the useful beam, the leakage radiation emitted from an x-ray tube should be shielded at all times. Diagnostic tube housings must be designed so that the radiation measured at a distance of 1 meter from the source does not exceed 100 mr in one hour when the tube is operated at its maximum rated output. Technique Indicators - Technique indicators are markings, selector switches, meters, etc. that are on the control panel, which tell the operator of the equipment what technique factors have been selected. They should not be confused with technique factors, which are the electrical potential (kvp), current (ma), exposure time parameters (seconds or pulses), or any combination of these parameters that are selectable at the control panel of an x-ray machine. Technique factors to be used during an exposure must be displayed on the technique indicators before the exposure begins. If automatic exposure controls are used, the technique factors that are set prior to exposure must be indicated on the control panel. If the technique factors for a given machine are fixed, the factors may be permanently marked directly on the control panel. Technique indicators must be visible from the operator's position, except in the case of spot films. Reproducibility of Exposures - For any specific combination of selected technique factors, the coefficient of variation of radiation exposures shall not exceed This parameter is checked by the medical physicist who inspects or calibrates the unit. It ensures consistency from one exposure to the next. Support of Patients and Films - It is sometimes necessary to support or restrain patients during radiographs so that proper positioning can be maintained and motion minimized. It may also be necessary to hold film cassettes, especially when portable x-ray units are used. When mechanical support of patient or film is necessary, mechanical means should be employed unless precluded by the procedure. Only as a last resort should a person be used to support a patient or a film during a radiograph. Pregnant women and individuals under 18 years of age should not be permitted to remain in the room during a radiograph. No person shall be used routinely to hold film or patients. When a patient or film must be held by an individual, these safety procedures must be followed: Except for patients who cannot be moved out of the room, only the individuals required for the medical procedure or training are permitted in the room during the radiographic or fluoroscopic examination. Individuals who must remain in the room with a patient during radiography or fluoroscopy may not place any part of their bodies in the primary beam of x rays and must be protected Page 5 of 19

6 by apparel (lead aprons and lead gloves) or devices (shielding barriers) of at least 0.25 mm of lead equivalent thickness. To assist in minimizing exposure, the radiologic technologist should carefully collimate to the area of clinical interest. Alternatively, an individual who must remain in the room with a patient being radiographed or fluoroscoped may be positioned in the radiography room so that radiation exposure does not exceed 2 millirem in any one hour or 100 millirem in any 7 consecutive days. This practice is not encouraged because it may be difficult to document the actual dose received by such individuals. Technique Guides - Technique guides are a set of predetermined technique factors that should be used for each routine radiographic x-ray procedure to be performed with a particular machine. Technique guides must be posted in the vicinity of each radiographic x-ray system's control panel and must contain the following information: Patient's anatomical size versus the technique factors to be utilized; The type and size of the film or screen-film combination to be used; The distance between the x-ray source and the film or image receptor; For automatic exposure control (AEC) systems (i.e.: systems with photomultiplier tubes or ionization chambers that terminate the exposure) with selectable exposure detectors and density settings, the technique guide must also specify the appropriate exposure detector(s) and density setting to be used for each radiographic exam listed; and For AEC systems operated in non-aec mode, the technique guide shall specify technique factors for each anatomical size, the type and size of the film or film-screen combination, and the distance between the x-ray source and film or image receptor. Patient Exposure Criteria - Procedures and auxiliary equipment designed to minimize patient and personnel exposure commensurate with needed diagnostic information shall be used. The optimum optical density, resolution, and contrast should be obtained on the film while the patient exposure should be minimized. X-ray films, intensifying screens, and other image recording devices should be as sensitive as is consistent with the requirements of the examination. Permitted Use of Portable and Mobile X-ray Equipment - Portable or mobile x-ray equipment may be used for examinations only when it is impractical to transfer the patient(s) to a stationary x-ray installation. Gonadal Shielding and Protection of Embryo/Fetus - Except when it would interfere with the diagnostic procedure, gonadal shielding of not less than 0.5 millimeter of lead equivalent must be used for patients who are not beyond reproductive age, during those radiographic procedures in which the gonads are in the useful beam. Protection of the embryo-fetus from radiation exposure during the radiological examination or treatment of a potentially pregnant woman should be given special consideration. 9.5 Quality Assurance Programs As defined by the National Council on Radiological Protection and Measurements ii (NCRP), Page 6 of 19

7 quality assurance is a management tool that includes policies and procedures designed to optimize the performance of facility personnel and equipment. All radiography operations at UIC should include a strong quality assurance program based on the recommendations of the NCRP. IEMA regulations require the following minimum quality control procedures for film processing systems. X-Ray Film Processing Systems - The darkroom safe light illumination darkroom operating procedures must prevent fogging of the unprocessed film. Requirements for manual film processing systems include: The use of a dedicated darkroom timer with an adjustable preset function so that the film processing time can be adjusted according to the solution temperature; The use of a dedicated darkroom thermometer to measure the solution temperature and allow for adjustment of film processing time; The use of a film processing guide that contains, as a minimum, information regarding time and temperature for film processing; and Change processing chemicals at a frequency appropriate for the conditions of use. Requirements for automated film processing include: Temperature of film processing must be appropriate for the type of film(s) being processed at the film transport speed selected; and The film processing chemicals and replenishing rate must be appropriate for the film transport speed selected; 9.6 Radiographic Systems (Excluding Fluoroscopic, Dental, Veterinary, and CT systems) The following rules do not apply to portable or mobile radiographic systems except where noted. Beam Limitation - The useful beam of the x-ray unit must be limited to the area of clinical interest. Stationary general purpose and portable/mobile equipment must be provided with an adjustable collimator with means for independent stepless adjustment of the size of the x-ray field. These units must also be equipped with a visual indicator so that the perimeter of the x- ray field can be visualized. This is usually accomplished with a light that illuminates the area that the primary x-ray beam will strike. A precise alignment of the x-ray field and the light field is required. If the light field is not almost perfectly aligned with the x-ray beam, the unit should be promptly serviced. Field Size and SID Indicators - Field size indicators, in units of inches or centimeters, must be provided and must be in close tolerance with the actual size of the beam. On most radiographic equipment, the distance between the focal spot of the x-ray tube (the source) and the image receptor (film or photomultiplier tube) can be adjusted. This distance is referred to as the source to image distance, or SID. Accurate SID indicators must also be provided. Since the distance between the collimator and the source is fixed, any change in the SID will change the Page 7 of 19

8 size of the x-ray field (assuming the collimator setting is not changed). Collimators, therefore, must be provided with field size scales for each SID that will be used. The units for distance marked on the collimator scale must be the same as the SID indicator (i.e. if the SID distance indicator is in inches, the collimator scale indicator must also be in inches). The unit should be promptly serviced if the SID being used does not have a corresponding scale on the collimator, if the indicated field size or SID indicators are inaccurate, or if the SID indicator and collimator SID scale are not calibrated in the same units. Source to Skin Distance (SSD) for Portable and Mobile Equipment - Portable and mobile x- ray equipment must be provided with means to prevent exposures at SSD's of less than 30 centimeters. Alignment of X-ray Field and Image Receptor - It is important that the central axis of the x-ray beam be perpendicular to the image receptor. The central axis of the beam should also strike the center of the image receptor. Each machine must have an indicator so the operator can determine that these alignments are proper. If the beam and image receptor are not properly aligned, the unit should be promptly serviced. Timers - Each x-ray machine must be provided with controls for terminating the exposure at a preset time interval, preset product of current and time (mas), preset number of pulses, or preset radiation exposure to the image receptor. If the timer has a setting of zero or off, exposure must not be possible at these settings. Arrangement of Exposure Controls - Each x-ray control shall be located in such a way as to meet the following requirements: Stationary x-ray systems and mobile or portable x-ray systems used as stationary x-ray systems must have the x-ray exposure switch permanently mounted behind a protective barrier. For mobile and portable single event exposures and configuration, the x-ray control must be positioned so that the operator is at least 6 feet away from the tube housing and the patient during an exposure. Manual Exposure Control Switches - Exposure control switches must be of the dead-man variety, meaning the operator must actively provide continuous pressure on the control to make an exposure. Controls must be incorporated into each x-ray system to terminate an exposure at any time except for exposures of 0.5 seconds or less. Page 8 of 19

9 Automatic Exposure Controls (AEC) - Systems that are provided with automatic exposure control devices shall incorporate a back-up timer to terminate the radiation exposure in the event of AEC failure. They must also have an indicator on the control panel showing when AEC mode is selected. A visible signal shall indicate when an exposure was terminated by the back-up timer, and manual resetting shall be required before further automatically timed exposures can be made. Entrance Exposure Limits - For a given beam filtration, the exposure rate at the surface of the patient varies with the source (focus) to skin distance and the kvp. Figure 9.1 illustrates this relationship. IEMA has established maximum entrance exposure limits for various medical radiographic exposures. These limits are specified for an average patient size and are intended to prevent unnecessary exposure of patients. These limits can be readily met by properly operating equipment, proper selection of film-screen combinations, and good film development techniques. Use of the settings recommended in the technique guides provided for each machine should ensure compliance with the IEMA limits. All of the IEMA limits and typical entrance doses for several common procedures are provided in the following Table 9.1. Note that these are exposure maxima. With careful selection of technique factors, adjustment of film processing systems, and choice of film and screen-film combinations, patient exposures can be further reduced. Every reasonable effort should be made to optimize the balance between these factors and desired image quality. The values found in NCRP 100 appear to be higher than the IEMA would permit primarily because the typical patient is larger in size than the IEMA selected patient thicknesses. Page 9 of 19

10 Table IEMA Requirements and Typical Exposures for Various X-Ray Exams IEMA Regulatory Requirements NCRP 100, 1989 Procedure Technique IEMA Specified Patient Thickness, cm Entrance Exposure Limit, mr Technique Typical Exposure, mr Chest, Grid, No Grid Abdomen (Kidneys, Ureters, B- ladder) Lumbo-Sacral Spine Cervical Spine Thoracic Spine NA NA NA Lumbar Spine NA NA NA ,953 3,446 1, , ,198 1,109 Full Spine (Chiropractic) NA NA NA 279 Skull Foot D/P NA NA Ribs NA NA NA Page 10 of 19

11 Table IEMA Requirements and Typical Exposures for Various X-Ray Exams IEMA Regulatory Requirements NCRP 100, 1989 Procedure Technique IEMA Specified Patient Thickness, cm Entrance Exposure Limit, mr Technique Typical Exposure, mr Shoulder NA NA NA Cholecystogram NA NA NA Upper GI NA NA NA Barium Enema NA NA NA Intravenous Pyelogram NA NA NA Pelvis NA NA NA Hip NA NA NA , ,012 1, ,341 1, Breast, 4.5 cm thick (American College of CC 4.5 cm 300 (ACR Recomme ndation) CC No Grid CC Grid 83 (ACR) 127 (ACR) Page 11 of 19

12 Table IEMA Requirements and Typical Exposures for Various X-Ray Exams IEMA Regulatory Requirements NCRP 100, 1989 Procedure Radiology Data) Technique IEMA Specified Patient Thickness, cm Entrance Exposure Limit, mr Technique Typical Exposure, mr Viewing System and Aural Communication - Windows, mirrors, closed circuit television, or an equivalent system must be provided to permit the operator to continuously observe the patient during the x-ray procedure. The operator must also be able to maintain continuous aural contact with the patient. Special Purpose X-ray Machines - Machines that are dedicated to a single purpose, such as mammography systems, computerized tomography systems, and radiation therapy simulators may have significantly different operating, equipment, and personnel qualification requirements, descriptions of which are beyond the scope of this manual. Only qualified personnel may operate these systems. Please contact the RSS if there are any questions about these requirements. 9.7 Fluoroscopic Systems Beam Limitation - The x-ray field shall be limited by stepless adjustable shutters. The minimum field size at the greatest SID shall be no greater that 5 cm by 5 cm. This system must be operational at all times, even when spot films are being taken. The x-ray beam may not significantly exceed the visible area of the image receptor. The collimator or shutters may temporarily increase to no larger than the size of any spot film being taken, but must return to the size of the input phosphor or smaller before fluoroscopy is restarted. This is usually an automatic process. Fluoroscopic Timer - Fluoroscopic units must be equipped with a manual reset, cumulative timer that will either indicate by an audible signal when 5 minutes of fluoroscopic beam on time has passed, or which must be manually reset at the end of 5 minutes. This is intended to remind operators of the amount of exposure time that has been received by the patient during a procedure. Page 12 of 19

13 Primary Barrier and Interlock - The entire cross section of the x-ray beam must be intercepted by a protective radiation shield or barrier, which is normally a part of the fluoroscopic image assembly, at any SID. This shield must be interlocked so that the beam cannot be switched on if it is not in place. The exposure rate due to transmission through the primary protective barrier is not permitted to exceed 2 mr per hour at 10 centimeters for each roentgen per minute of entrance exposure. Source-Skin Distance (SSD) - In order to protect the patient from excessive exposure and to ensure proper image quality, the SSD may not be less than the following values: stationary fluoroscopes - 30 cm; mobile fluoroscopes - 20 cm; fluoroscopes specifically designed for examinations of extremities cm. These distances are fixed on equipment with the tube mounted under the table. When the fluoroscopy tube is above the table, the proper distance is usually maintained by a fixed collimator, but in some cases the equipment design may allow improper SSDs. In these cases it is important for the operator to be aware of the limitation of the equipment and maintain the minimum required SSD. Current and Voltage Indicators - During fluoroscopy and recording of fluoroscopic images, the kv and ma must be continuously indicated at the control panel and/or the operator's position. Dead Man Switch - X-ray production in the fluoroscopic mode must be controlled by a device that requires continuous pressure by the operator for the entire time of any exposure. This device is frequently a foot switch. Entrance Exposure Rate Requirements - Depending on the type of fluoroscopy unit, the maximum permissible exposure rate at the point where the fluoroscopy beam enters the patient is limited to 5, 10, or 20 roentgens per minute. These exposure rates are checked during annual equipment inspections and should be checked after any repair that might affect the x-ray output. Machines that are permitted to boost the output to 20 roentgens per minute must be equipped with a separate high level control that is manually and continuously activated. A continuous signal audible to the operator must also be provided during the exposure that indicates the high level control is being employed. Use of Lead Aprons - The operator, all assistants, and all observers in the fluoroscopy room (including surgical suites and the cardiac catheterization lab) are required to be protected from scattered radiation by protective aprons of not less than 0.25 millimeter lead equivalent or whole body protective barriers while the x-ray beam is on. Control of Scattered Radiation - For fluoroscopic systems with the x-ray tube mounted below the table, the table shall be equipped with a bucky slot cover equivalent to 0.25 millimeter lead equivalent to shield the scattered radiation emanating from below the table. Except when sterile fields or special procedures contraindicate their use, overlapping protective drapes, hinged or sliding panels, or other shielding must be provided and used to intercept scattered radiation that would otherwise reach the operator and other individuals near the machine. This shielding is not intended to substitute for protective lead aprons. Cardiac Catheterization Requirements - Protective barriers shall be available for use by individuals whose presence is required in the room during activation of the x-ray tube. If a protective barrier includes or consists of a transparent viewing panel, the viewing panel shall afford protection of not less than 0.5 millimeter of lead equivalent. Page 13 of 19

14 Because modern equipment allows great flexibility in the direction of the beam, IEMA recommends that individuals in the room should step back from the x-ray system and remain behind protective barriers during activation of the x-ray tube(s) whenever possible. 9.8 CT Systems Facility Design - The control panel must be located behind a protective barrier. A two-way aural communication system must be provided between the patient and the operator at the control panel. A viewing system must be provided to permit continuous viewing of the patient during the scan, and must be located in a position that allows observation of the patient from the control panel. Indicators - The CT x-ray control panel and gantry must be equipped with beam-on and shutter status indicators. The control panel must visually display the technique factors, tomographic section thickness, and scan increment prior to the initiation of a scan or series of scans. Exposure Termination Devices - Equipment failures that affect data collection must cause the x-ray source to de-energize and must visually indicate that de-energization has occurred. The operator must also have a means of terminating any x-ray exposure greater than 0.5 second in duration. Tomographic Plane Indication and Alignment - A visual means to determine the location of a reference plane must be provided, which can be offset from the location of the tomographic planes. If this device is a light, the illumination level must be visually observable under ambient light conditions of up to 500 lux (45 foot-candle). The total error in the indicated location of the tomographic plane or reference plane shall not exceed 5 millimeters. Operating Procedures - Information must be available at the control panel regarding the operation of the system. This information must include written quality assurance procedures. Quality Assurance (QA) Procedures - Written QA procedures must be developed by a qualified diagnostic imaging specialist, who must meet IEMA requirements (usually a medical or health physicist). The procedures must specify the tests that must be performed, instructions to be employed when performing the tests, the frequency of each test, acceptable test results, and actions to be taken when unacceptable test results are obtained. A test procedure for measuring the resolution of the system using a CT phantom must be included in the QA procedures. Periodic Inspections - A qualified diagnostic imaging specialist, usually a medical physicist, must perform annual dose measurements on each CT system. Additional measurements must be made after any service of the equipment that could cause a change in the radiation output. Required Records - Written records of the radiation dose measurements and QA testing must be maintained. Records must include the date of the test, the identity of the person performing the test, the type of test performed, and a notation that test results were acceptable or unacceptable. 9.9 Mammography Systems The Mammography Quality Standards Act of 1992 (MQSA) requires that after October 1, 1994, all mammography facilities conducting breast cancer screening or diagnosis be certified by the Page 14 of 19

15 U.S. Food and Drug Administration (FDA). Certification must be obtained through an FDA approved accreditation body. After certification has been approved, the FDA issues an MQSA certificate that must be displayed where it can be viewed by mammography examinees (patients). The Radiology Department of the University of Illinois Hospital has obtained mammography certification and the MQSA certificate has been posted for viewing as required. To become certified, mammography facilities must meet quality standards for personnel, equipment, maximum allowable radiation dose, quality assurance, medical audit and outcome analysis (a system to track positive mammographic findings), and record keeping and reporting. Annual surveys must be conducted by a qualified medical physicist and the facility must undergo periodic audits and/or clinical image reviews by the accreditation body Radiation Safety Requirements for Use of Therapeutic Equipment Regulations for radiation therapy equipment are specified in two parts: therapy systems operating below 1 MeV and systems operating above 1 MeV. Refer to Sections and of the IDNS regulations for complete details. Some of the important requirements are summarized below Therapy Systems Operating Below 1 MeV Interlocks - For systems operating above 150 kev, every door to the room must be equipped with an interlock that will automatically terminate the generation of x-rays when the door is opened. If the door is opened for any reason with the x-ray beam on, the interlock will terminate the beam and prevent generation of x rays until the door is closed and the controls are reset at the control panel. Doors - The doors to the therapy room must be able to be opened from the inside at all times. Warning Lights - Warning lights that are readily visible at all entrances to the therapy room must be provided that indicate when the x-ray beam is on.location of Control Panel and Operator - The control panel must be located outside the therapy room. This is to ensure the operator is outside the room when x-rays are being produced. Viewing System - Windows, mirrors, closed-circuit television, or an equivalent system must be provided so that the operator, while at the control panel, can maintain continuous visual observation of the patient during treatment. Communication - Two-way aural communication must be provided so that the operator, while at the control panel, can verbally communicate with the patient during treatment. Equipment Requirements - Extensive equipment requirements are outlined in the IEMA regulations regarding tube housing leakage limits, beam limiting devices, filter systems, tube/aperture alignment, tube housing stability, SSD indicators, timers, tube potential, and current indicators, etc. Quality Assurance - Extensive quality assurance requirements are imposed on use of radiation therapy equipment including output measurements, half-value layer measurements, alignment of the radiation field, and the beam limiting device, etc. Page 15 of 19

16 Operating Procedures - Written operating procedures must be provided and include safety oriented instructions Therapy Systems Operating Above 1 MeV Most radiation therapy machines operating above 1 MeV are linear accelerators. Many of the regulations are similar to rules for machines below 1 MeV including those regarding facility design, interlocks, warning lights, viewing systems, aural communication, location of control panel, locations of emergency off buttons, permissible leakage radiation, beam limiting devices, SSD indicators, filters, etc. They also address other topics such as beam monitoring systems, beam symmetry, and selectors for beam energy and treatment mode. Quality assurance requirements are significantly more extensive Dental Radiographic Systems All of the requirements in sections 9.2, 9.3, 9.4 and 9.5 apply to dental radiographic systems. In addition, the following rules and recommendations apply: Dental Fluoroscopy - The requirements outlined in Section 9.7 also apply to dental fluoroscopy Timers - Dental X-ray equipment must be provided with timers that terminate the exposure at a preset time interval, preset product of current and time (mas), preset number of pulses, or preset radiation exposure to the image receptor. If the timer has a setting of zero or off, exposure must not be possible at these settings. Exposure Control Switches - Exposure control switches must be of the dead-man variety, meaning that the operator must actively provide continuous pressure on the control to make an exposure. This dead-man switch must be located behind a protective barrier or at least 6 feet from the patient and the tube housing during an exposure. Controls must be incorporated into each system to terminate an exposure at any time except at exposures of 0.5 seconds or less. Personnel Protection - If the operator is not behind a protective barrier during an exposure, a distance of at least 6 feet from the patient and the tube housing must be maintained and the operator must wear a protective apron of at least 0.25 mm lead equivalent to protect against scattered radiation. Personnel who are required to be in the room during a radiograph, such as a parent restraining a child, must also wear protective aprons of at least 0.25 mm lead equivalent. Patient and Film Holding Devices - Patient and film holding devices must be used when the techniques permit. Shielding of the Patient - In addition to the general advice provided in Appendix K, the following recommendations made by the American Dental Association iii should be followed: "Radiation exposure to the gonads and the thyroid glands may be negligible for properly conducted radiographic examinations. However, leaded aprons and collars should be used to minimize any unnecessary radiation." Source-Skin Distance (SSD) and Beam Limitation - Systems designed for use with an intraoral film or image receptor maintain a source-skin distance of at least 18 cm for units that can operate above 50 kvp, or 10 cm if the unit operates at or below 50 kvp. This is necessary Page 16 of 19

17 to provide an x-ray beam that is as parallel as possible, thereby creating an image that is free from serious geometry effects. A means to limit the size of the beam that strikes the patient to a circle having a diameter of no more than 7 centimeters must also be provided so that only the area of clinical interest is exposed to the beam. Dental radiographic units are usually provided with a cylindrically shaped collimator that limits the beam size and maintains a proper SSD. Dental Radiographic Exposure Limits (Single Film) - The entrance exposure to an adult patient for a routine intraoral bitewing exam may not exceed the limit specified for the kvp used as shown below in Table 9.2. Use linear interpolation for x-ray potentials that are not listed in the table. The IEMA regulations indicate that this table was determined empirically by a panel of dentists in a U.S. FDA study, but a more specific reference is not cited. The American Dental Association 2 recommends speed "E" film for periapical and bitewing radiographs, and the use of the fastest possible film-intensifying screen combinations for extraoral radiography. They state that exposures in the range of 60 to 100 kvp are suitable for most purposes. Within this range, lower kilovoltages are associated with higher subject contrast, higher entrance skin doses, lower deep tissue doses, and lower levels of scattered radiation. Higher kilovoltages are associated with lower subject contrast, lower entrance skin doses, higher deep tissue doses, and higher levels of scattered radiation. When good film processing techniques are employed, doses lower than those shown in the table can be achieved. The proper balance between acceptable image quality and reduction of patient dose is often a matter of professional judgment. TABLE IEMA ENTRANCE EXPOSURE LIMITS FOR DENTAL BITEWING X-RAY EXAMINATIONS Potential kvp "D" Speed (UltraSpeed) Film mr "E" Speed (EctaSpeed) Film mr Page 17 of 19

18 TABLE IEMA ENTRANCE EXPOSURE LIMITS FOR DENTAL BITEWING X-RAY EXAMINATIONS Potential kvp "D" Speed (UltraSpeed) Film mr "E" Speed (EctaSpeed) Film mr Tube Housing - The tube housing and position indicating device shall not be hand-held during exposure Extraoral Systems - Dental rotational panoramic systems must be provided with means to limit the x-ray beam to the size of the imaging slit in the transverse axis, and to a total of no more than 13 cm larger than the imaging slit in the vertical axis. Other systems (e.g., cephalometric) must be provided with means to accurately size and align the x-ray beam with the image receptor Human Research As applied to this section, human research means the application of machine produced radiation to human subjects with the primary goal of advancing scientific knowledge, not diagnosis or therapy. Review of human research is mandated by Food and Drug Administration regulations to ensure that the research is conducted in a safe manner using willing volunteers for subjects. All proposed human research must be approved in advance by an Institutional Review Board (IRB). Research subjects must be fully informed of the risks involved with the research and must indicate their willingness to participate by completing informed consent forms. The UIC IRB is under the auspices of the Office for Protection from Research Risks (extension ), a section of the Office of the Vice Chancellor for Research. If x-ray procedures are part of a research study, the radiation doses to the subjects must be evaluated. The limits for radiation dose equivalent presented in Table 9.3 are based on regulations established by the FDA iv. A qualified medical physicist, health physicist, or radiologist shall be consulted to ensure doses will not exceed these values. If the radiation dose to the subject will exceed these limits, the Radiation Producing Machines Subcommittee of the UIC Radiation Safety Committee must review and approve the study in advance. Page 18 of 19

19 TABLE PERMISSIBLE X-RAY DOSES TO SUBJECTS OF RESEARCH STUDIES AT UIC PERMISSIBLE DOSE EQUIVALENTS RT OF BODY 18 YEARS OR OLDER UNDER 18 YEARS Whole Body, Active Blood-Forming Organs, Lens of Eye, and Gonads All Other Organs Single Dose - 3 rem Annual Total - 5 rem Single Dose - 5 rem Annual Total - 15 rem Single Dose rem Annual Total rem Single Dose rem Annual Total rem References i. Radiological Health Handbook, Revised Edition, January 1970, U.S. Department of Health Education and Welfare, Public Health Service, Food and Drug Administration, Bureau of Radiological Health, Rockville, Maryland. ii. Quality Assurance for Diagnostic Imaging Equipment, NCRP Report No. 99, National Council on Radiation Protection and Measurements, Bethesda, MD, NCRP, iii. Recommendations in Radiographic Practices: An Update, 1988, American Dental Association, Journal of the American Dental Association, JADA, 118, , iv. Food and Drug Administration Regulations, 21 CFR Section 361.1(b)(3). Page 19 of 19