NAC459.580. Intraoral dental radiographic systems.

     1. In addition to the provisions of NAC 459.552 to 459.558, inclusive, and 459.564, these requirements apply to X-ray equipment and associated facilities used for dental radiography. The criteria for extraoral dental radiographic systems are covered in NAC 459.616 to 459.624, inclusive.

     2. X-ray systems designed for use with an intraoral image receptor must be provided with means to limit source-to-skin distance of not less than 18 centimeters.

     3. Radiographic systems which are designed for use with an intraoral image receptor must be provided with means to limit the X-ray beam so that:

     (a) If the minimum source-to-skin distance is 18 centimeters or more, the X-ray field at the minimum source-to-skin distance is containable in a circle having a diameter of no more than 7 centimeters; and

     (b) If the minimum source-to-skin distance is less than 18 centimeters, the X-ray field at the minimum source-to-skin distance is containable in a circle having a diameter of no more than 6 centimeters.

     4. A means must be provided to terminate the exposure at a preset time interval, a preset product of current and time, a preset number of pulses, or a preset radiation exposure to the image receptor. In addition:

     (a) Termination of exposure must cause automatic resetting of the timer to its initial setting or to zero; and

     (b) It must not be possible to make an exposure when the timer is set to a zero or off position if either position is provided.

     5. When four timer tests taken at identical timer settings equal 0.5 seconds or less, the average time period (T) must be greater than or equal to five times the difference between the maximum period (T max) and the minimum period (T min) in accordance with the formula: T 5 (T max-T min).

     6. Deviation of measured technique factors from indicated values of kVp and exposure time must not exceed the limits specified for that system by its manufacturer. In the absence of the manufacturer’s specifications, the deviation must not exceed 10 percent of the indicated value for kVp and 20 percent for exposure. All timers must be accurate to within ±20 percent of the selected value.

     7. A control must be incorporated into each X-ray system so that an exposure can be terminated at any time, except for exposures of one-half second or less. The control switch must be of the dead-man type.

     8. Each X-ray control must be located to meet the following criteria:

     (a) Each installation must be provided with a protective barrier for the operator or must be so arranged that the operator can stand at least 6 feet from the patient and well away from the useful beam; and

     (b) The X-ray control must provide visual indication observable at or from the operator’s protected position whenever X rays are produced. In addition, a signal audible to the operator must indicate that the exposure has terminated.

     9. The exposure produced must be reproducible to within the following criteria: When all technique factors are held constant, the coefficient of variation must not exceed 0.10. This requirement is met if, when four exposures at identical technique factors are made, the value of the average exposure (E) is greater than or equal to five times the difference between the maximum exposure (E max) and the minimum exposure (E min) in accordance with the formula: E 5 (E max-E min).

     10. Patient and film holding devices must be used when the techniques permit.

     11. Neither the tube housing nor the position indicating device may be handheld during an exposure.

     12. The X-ray system must be arranged and operated in such a manner that the useful beam at the patient’s skin does not exceed the dimensions specified in subsection 3.

     13. Dental fluoroscopy without image intensification must not be used.

     14. Each patient undergoing dental radiography must be draped with a protective apron of not less than 0.25 millimeters lead-equivalent to cover the gonadal area.

     15. Dental X-ray machines with a nominal fixed kVp of less than 50 kVp must not be used to make diagnostic dental radiographs of humans.

     [Bd. of Health, Radiation Control Reg. §§ 6.7-6.7.6.5, eff. 2-28-80]—(NAC A by R185-08, 5-7-2010)