Dental Radiographic Systems

(A) General Requirements. (1) Timers. Means shall be provided to terminate the exposure at a preset time interval, preset product of current and time, a preset number of pulses, or a preset radiation exposure to the image receptor. In addition, it shall not be possible to make an exposure when the timer is set to a "zero" or "off" position if either position is provided. (2) Reproducibility. With a timer setting of 0.3 second or less, the average exposure period max (T) shall be greater than or equal to five times the maximum exposure period (T ) minus min the minimum exposure period (T ) when 4 timer tests are performed: max min T > 5(T - T ) (3) X-ray Control. (a) An x-ray control shall be incorporated into each x-ray system such that an exposure can be terminated by the operator at any time, except for exposures of 0.5 second or less. (b) The exposure switch shall be of the dead-man type. (c) Each x-ray control shall be located in such a way as to permit the operator to remain in an area of less than two millirems in any one hour during the entire exposure. (4) Exposure Reproducibility. The coefficient of variation shall not exceed 0.10 when all technique factors are held constant. This requirement shall be deemed to have been met if, when four Exposures are made at identical technique factors, the value of the average max Exposure (E) is greater than or equal to five times the maximum Exposure (E ) minus the min minimum Exposure (E ): max min E > 5(E - E ) (B) Additional Requirements for Dental Intraoral Systems. (1) Source-to-skin Distance (SSD). X-ray systems designed for use with an intraoral image receptor shall be provided with means to limit SSD to not less than: (a) 18 centimeters if operable above 50 kVp; or, (b) ten centimeters if not operable above 50 kVp. (2) Field Limitation. (a) Radiographic systems designed for use with an intraoral image receptor shall be provided with means to limit the x-ray beam such that the x-ray field, at the minimum SSD. shall be containable in a circle having a diameter of no more than seven centimeters. (b) An open-ended beam-indicating device shall be used. (C) Additional Requirements for Dental Extraoral System Field Limitation. (1) Dental rotational panoramic systems shall be provided with means to limit the x-ray beam to the imaging slit in the transverse axis and shall not exceed a total of 0.5 inch larger than the imaging slit in the vertical axis. (2) All other dental extraoral radiographic systems (e.g., cephalometric) shall be provided with means to both size and align the x-ray field so that it does not exceed beyond any edge of the image receptor by more than 2% of the SID. (D) Additional Requirements Applicable to Certified Systems Only. Only diagnostic x-ray systems incorporating one or more certified component(s) shall be required to comply with the following additional requirement(s) which relate to that certified component(s). (1) Reproducibility. When the equipment is operated on an adequate power supply as specified by the manufacturer, the estimated coefficient of variation of radiation Exposure shall be no greater than 0.05, for any specific combination of selected technique factors. (2) Linearity. When the equipment allows a choice of x-ray tube current settings and is operated on a power supply as specified by the manufacturer in accordance with the requirements of applicable Federal standards, for any fixed x-ray tube potential within the range of 40 to 100% of the maximum rating, the average ratios of Exposure to the indicated milliampere-seconds product obtained at any 2% consecutive tube current settings shall not differ by more than 0.10 times their sum: X -X # 0.10 (X + X ) where: X and X are the average mR/mAs values obtained at each of two consecutive tube current settings. (3) Accuracy. Deviation of technique factors from indicated values shall not exceed the limits specified for that system by its manufacturer. (4) Timers. Termination of exposure shall cause automatic resetting of the timer to its initial setting or to "zero". (5) Beam Quality. All certified dental x-ray systems manufactured on and after December 1, 1980, shall have a minimum half-value layer not less than 1.5 millimeters aluminum equivalent. Systems operating above 70 kVp are subject to the filtration requirements of 105 CMR 120.404(E)(1). (E) Additional Operation Controls for Dental Radiographic Systems. (1) Film holding devices shall be used except in individual cases in which the practitioner has determined that such holding are contraindicated. Written safety procedures required by 105 CMR 120.400 shall state the criteria under which the exception shall apply. (2) The tube housing support shall be constructed and adjusted so that the tube housing shall not drift from its set position during an exposure. Neither the tube housing nor the support housing shall be hand-held during an exposure. (3) The operator shall stand at least six feet from the useful beam or behind a protective barrier. Where a protective barrier is utilized, a viewing system shall be used. (4) Individuals who operate only dental radiographic systems are exempt from the personnel monitoring requirements of 105 CMR 120.211. (5) Protective equipment -aprons and shields-shall be checked annually for defects, such as holes, cracks, and tears to assure reliability and integrity and documentation shall be kept for five years. (6) Thyroid shields shall be used on all patients, when applicable. (7) The registrant of the facility shall ensure that the equipment is in safe operating condition: (a) when it is first installed and prior to use on patients; (b) after any major changes or replacement of parts and prior to use on patients: (c) by having calibrations and preventative maintenance: 1. such preventative maintenance or calibrations shall not exceed three years 2. the preventative maintenance or calibrations shall be performed by a registered service provider as specified in 105 CMR 120.026. (d) Preventative maintenance and calibrations shall be reviewed and signed within a reasonable time of completion of the tests but no longer than 30 days of completion of the tests by the licensed dentist, and any necessary corrective action shall be implemented within 30 days. (e) Records of the last two calibrations and preventative maintenance shall be maintained at the facility. (F) Hand-held Intraoral Dental Radiographic Units. (1) For all uses: (a) Operators of hand-held intraoral dental radiographic units shall be specifically trained to operate such equipment. (b) When operating a hand-held intraoral dental radiographic unit, operators shall wear a lead apron and thyroid collar, unless otherwise authorized by the Agency or a qualified health or medical physicist. (c) A hand-held intraoral dental radiographic unit shall be held without any motion during a patient examination. A tube stand may be utilized to immobilize a hand-held intraoral dental radiographic unit during patient examination. (d) Unless otherwise authorized by the Agency, a hand-held intraoral dental radiographic unit shall be used with a secondary radiation block. (e) The operator shall ensure there are no bystanders within a radius of at least six feet from the patient being examined with a hand-held intraoral radiographic unit. (2) Additional requirements for operatories in permanent facilities: (a) Hand-held intraoral dental radiographic units shall be used for patient examinations in dental operatories that meet the structural shielding requirements specified by the Agency or by a qualified health or medical physicist. (b) Hand-held intraoral dental radiographic units shall not be used for patient examinations in hallways and waiting rooms. (G) Cone Beam 3-D Dental Imaging Systems. (1) Facilities shall maintain documentation of applications from the manufacturer; (2) Operators of the unit shall be a: (a) Licensed Dentist or (b) Licensed Hygienist or Certified Dental Assistant (3) All facilities that use a Cone Beam CT unit shall follow the manufacturer's recommendations for Quality Control; (4) All facilities shall perform calibrations and preventative maintenance annually. (5) Preventative maintenance, surveys, and calibrations shall be reviewed and signed within a reasonable time of completion of the tests but no longer than 30 days of completion of the tests by a qualified medical physicist and the licensed dentist and any necessary corrective action shall be implemented within 30 days.