Intraoral Dental Radiographic Systems

Intraoral Dental Radiographic Systems. In addition to the provisions of 1.6.3and 1.6.4, the requirements of 1.6.7 apply to x-ray equipment and associated facilities used for dental radiography. Requirements for extraoral dental radiographic systems are covered in 1.6.6. 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. 10 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 field such that the x-ray field at the minimum SSD shall be containable in a circle having a diameter of no more than 7 centimeters; and b. An open ended PID (position indicating device) shall be used on new dental x-ray equipment purchased after the effective date of these regulations. 3. Radiation Exposure Control for Certified and Noncertified Systems. a. Exposure Initiation. i. Means shall be provided to initiate the radiation exposure by a deliberate action on the part of the operator, such as the depression of a switch. Radiation exposure shall not be initiated without such an action; and ii. 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. b. Exposure Termination. i. 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. ii. An x-ray exposure 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 1/2 second or less. iii. Termination of an exposure shall cause automatic resetting of the timer to its initial setting or to "zero". c. Exposure Indication. Means shall be provided for visual indication observable at or from the operator's protected position whenever x-rays are produced. In addition, a signal audible to the operator shall indicate that the exposure has terminated. d. Exposure Duration (Timer) Reproducibility. With a timer setting of 0.5 seconds or less, the difference between the maximum exposure time (Tmax) and the minimum exposure time (Tmin) shall be less than or equal to 10% of the average exposure time ( ), when four timer test are performed: e. Exposure Control Location and Operation Protection. i. Stationary x-ray systems shall be required to have the x-ray exposure control permanently mounted in a protected area, so that the operator is required to remain in that protected area during the entire exposure; and ii. Mobile and portable x-ray systems which are: i. used for greater than one week in the same location, i.e., a room or suite, shall meet the requirements of 1.6.7(3)(e)(i); and ii. used for less than one week in the same location, shall be provided with either a protective barrier at least 6.5 feet (2m) high for operator protection, or means to allow the operator to be at least 12 feet (3.7 m) from the tube housing assembly while making exposures. 4. Exposure Reproducibility. The coefficient of variation shall not exceed 0.05 when all technique factors are held constant. This requirement shall be deemed to have been met if, when 4 exposures are made within a period of one hour at identical technique factors, the difference between the maximum exposure value (Emax) and the minimum exposure value (Emin) shall be less than or equal to 10% of the average exposure ( ): 5. 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 any fixed x-ray tube potential within the range of 40 to 100 percent of the maximum rating, the average ratios of exposure to the indicated millampere-seconds product obtained at any 2 consecutive tube current settings shall not differ by more than 0.10 times their sum: where and are the average mR/mAs (C/kg/mAs) values obtained at each of 2 consecutive tube current settings. 6. Accuracy. Deviation of technique factors from indicated values shall not exceed the limits specified for that system by its manufacturer. In the absence of manufacturer's specifications, the deviation shall not exceed 10% of the indicated value. 7. kVp Limitations. Dental x-ray machines with a nominal fixed kVp of less than 50 kVp shall not be used to make diagnostic dental radiographs of humans. 8. Administrative Controls. a. Patient and film holding devices shall be used when the techniques permit. b. The tube housing and the PID shall not be hand held during an exposure. c. The x-ray system shall be operated in such a manner that the useful beam at the patient's skin does not exceed the requirements of 1.6.7(2). d. Dental fluoroscopy without image intensification shall not be used.