In addition to the provisions of 602 and 603 [Sections 602 and 603 of 20.3.6.602 and 603 NMAC], the requirements of this section apply to x-ray equipment and associated facilities used for dental radiography. Criteria for extraoral dental radiographic systems are covered in 605 [Section 605 of 20.3.6.605 NMAC].

1. A. Source-to-Skin Distance: X-ray systems designed for use with an intraoral image receptor shall be provided with means to limit source-to-skin distance to not less than:

   (1) 18 cm (7.09 inches) if operable above 50 kVp; or

   (2) 10 cm (3.93 inches) if not operable above 50 kVp.

2. B. Field Limitation:

   (1) Radiographic systems designed for use with an intraoral image receptor shall be provided with means to limit the x-ray beam such that:

   (a) if the minimum source-to-skin distance (SSD) is 18 cm (7.09 inches) or more, the x-ray field, at the minimum SSD, shall be containable in a circle having a diameter of no more than 7 cm (2.76 inches); and

   (b) if the minimum SSD is less than 18 cm, (7.09 inches) the x-ray field, at the minimum SSD, shall be containable in a circle having a diameter of no more than 6 cm (2.36 inches).

3. C. 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:

   (1) Termination of exposure shall cause automatic resetting of the timer to its initial setting or to zero;

   (2) It shall not be possible to make an exposure when the timer is to a zero or off position if either position is provided;

   (3) Reproducibility: With a timer setting of 0.5 seconds or less, the average exposure period (T) shall be greater than or equal to 5 times the maximum exposure period (Tmax) minus the minimum exposure period (Tmin) when 4 timer tests are performed: T 5(Tmax Tmin).

4. D. X-ray Control (use of dead-man timers):

   (1) A control shall be incorporated into each x-ray system such that an exposure can be terminated at any time, except for exposures of one-half second or less;

   (2) Each x-ray control shall be located in such a way as to meet the following criteria:

   (a) for stationary x-ray systems, it shall be required that the control switch be permanently mounted in a protected area (e.g., corridor outside the room) so that the operator is required to remain in that protected area during the entire exposure;

   (b) for mobile and portable x-ray systems which are:

   (i) used for greater than 1 week in one location (one room or suite) shall meet the requirements of 606.D.2.a [Subparagraph (a), Paragraph (2), Subsection D., Section 606 of 20.3.6.606 NMAC];

   (ii) used for more than 1 hour and less than 1 week at one location (one room, or suite) shall meet the requirements of 606.D.2.b.(1) [Item (i), Subparagraph (b), Paragraph (2), Subsection D., Section 606 of 20.3.6.606 NMAC]] or be provided with 1.98 m (6.5 feet) high protective barrier which is placed at least 1.83 m (6 feet) from the tube housing assembly and at least 1.83 m (6 feet) from the patient;

   (iii) used to make an exposure(s) of only one patient at the use location shall meet the requirement of 606.D.2.b.(1) or 606.D.2.b.(2) [Items (i) or (ii), Subparagraph (b), Paragraph (2), Subsection D., Section 606 of 20.3.6.606 NMAC] or be provided with a method of control which will permit the operator to be a least 3.63 m (12 feet) from the tube head assembly during an exposure.

   (3) The x-ray control shall 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 shall indicate that the exposure has terminated; and

   (4) From the operator's position, the patient must be capable of being viewed directly or via mirrors.

5. E. Exposure Reproducibility: The exposure produced shall be reproducible to within the following criteria: When all technique factors are held constant, the coefficient of variation shall not exceed 0.10. This shall be deemed to have been met if when four exposures at identical technique factors are made that the value of the average exposure (E) is greater than or equal to five times the maximum exposure (Emax) minus the minimum exposure (Emin). E>5 (Emax Emin)

6. F. Operating Controls:

   (1) Patient and film holding devices shall be used when the techniques permit. The safety rules, required by 602.A.1.d [Subparagraph (d), Paragraph (1), Subsection A., Section 602 of 20.3.6.602 NMAC], shall list individual projections where holding devices cannot be utilized.

   (2) Neither the tube housing nor the position indicating device shall be hand-held during an exposure.

   (3) The x-ray system shall be arranged and operated in such a manner that the useful beam at the patient's skin does not exceed the dimensions specified in 606.B.1.a or 606.B.1.b [Subparagraphs (a) or (b), Paragraph (1), Subsection B., Section 606 of 20.3.6.606 NMAC].

   (4) Dental fluoroscopy shall be prohibited.

   [5-3-95; 20.3.6.606 NMAC – Rn, 20 NMAC 3.1.6.606, Recompiled xx/xx/xx]