Intraoral dental radiographic systems

In addition to the requirements of sections 33.1-10-06-03 and 33.1-10-06-04, 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 section 33.1-10-06-06. Only systems meeting the requirements of this section shall be used. 1. 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: a. Eighteen centimeters if operable above fifty kilovolts peak. b. Ten centimeters if operable at fifty kilovolts peak only. 2. Beam limitation. Radiographic systems designed for use with an intraoral image receptor shall be provided with means to limit the x-ray beam such that: a. The x-ray beam, at the minimum source-to-skin distance, shall be containable in a circle having a diameter of no more than seven centimeters. b. An open-ended shielded position indicating device shall be used. The shielding shall be equivalent to the requirements of subsection 4 of section 33.1-10-06-04. 3. Radiation exposure control. a. Exposure initiation. (1) 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. (2) 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 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. c. Exposure termination. (1) 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. (2) 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 one-half second or less. (3) Termination of an exposure shall cause automatic resetting of the timer to its initial setting or to "zero". d. Exposure duration (timer) linearity. For systems having independent selection of exposure time settings, the average ratios (X1) of exposure to the indicated timer setting, in units of coulombs per kilogram per second [milliroentgen per second], obtained at any two clinically used timer settings shall not differ by more than ten hundredths times their sum. (X1 - X2) < 0.1 (X1 + X2) where X1 and X2 are the average values. e. Exposure control location and operator protection. (1) 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 so the operator can view the patient while making the exposure. (2) Mobile and portable x-ray systems which are: (a) Used for greater than one week in the same location, i.e., a room or suite, shall meet the requirements of paragraph 1. (b) Used for less than one week in the same location shall be provided with either a protective barrier at least two meters [6.5 feet] high for operator protection, or means to allow the operator to be at least two and seven-tenths meters [9 feet] from the tube housing assembly while making exposures. (3) Hand-held dental x-ray equipment: (a) Operators shall use all safety devices and follow safety procedures according to the manufacturer. (b) Operators shall wear a protective apron during exposure in accordance with subparagraph b of paragraph 6 of subdivision a of subsection 1. (c) Operators shall have dose monitoring in accordance with section 33.1-10-04.2-01 [10 CFR 20.1502]. 4. Reproducibility. When the equipment is operated on an adequate power supply as specified by the manufacturer, the estimated coefficient of variation of radiation exposures shall be no greater than five hundredths for any specific combination of selected technique factors. 5. mA/mAs linearity. The following requirements apply when the equipment is operated on a power supply as specified by the manufacturer for any fixed x-ray tube potential within the range of forty percent to one hundred percent of the maximum rated. a. Equipment having independent selection of x-ray tube current (mA). The average ratios (X1) of exposure to the indicated milliampere seconds product, in units of coulombs per kilogram per milliampere second (or milliroentgen per milliampere seconds), obtained at any two consecutive tube current settings shall not differ by more than ten hundredths times their sum: X1 - X2 < 0.10 (X1 + X2) where X1 and X2 are the average values obtained at any two consecutive tube current settings, or at two settings differing by no more than a factor of two where the tube current selection is continuous. b. Equipment having a combined x-ray tube current exposure time product (mAs) selector, but not a separate tube current (mA) selector. The average ratios (X1) of exposure to the indicated milliampere-seconds product, in units of coulombs per kilogram per milliampere second (or mR/mAs), obtained at any two consecutive mAs selector settings shall not differ by more than ten hundredths times their sum: X1 - X2 < 0.10 (X1 + X2) where X1 and X2 are the average values obtained by any two mAs selector settings, or at two settings differing by no more than a factor of two where the mAs selector provides continuous selection. c. Measuring compliance. Determination of compliance shall be based on ten exposures taken within a time period of one hour, at each of the two settings. These two settings may include any two focal spot sizes except where one is equal to or less than forty-five hundredths millimeters and the other is greater than forty-five hundredths millimeters. For purposes of this requirement, focal spot size is the nominal focal spot size specified by the x-ray tube manufacturer. 6. Accuracy. Deviation of technique factors from values for kVp and exposure time (if time is independently selectable) shall not exceed the limits specified for that system by its manufacturer. In the absence of manufacturer's specifications, the deviation shall not exceed ten percent of the indicated value for kVp and twenty percent for time. 7. kVp limitations. Dental x-ray machines with a nominal fixed kVp of less than fifty kVp shall not be used to make diagnostic dental radiographs of humans. 8. Beam quality. All dental x-ray systems are subject to the filtration requirements of subdivision a of subsection 5 of section 33.1-10-06-04 9. Administrative controls. a. Patient and film holding devices shall be used when the techniques permit. b. The tube housing and the position indicating device shall not be handheld during an exposure unless the system was specifically designed as a hand-held dental x-ray machine. 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 subdivision a of subsection 2. d. Dental fluoroscopy without image intensification shall not be used. e. Security for portable dental systems. A means shall be provided to prevent unauthorized use whenever the x-ray system is not under the control and constant surveillance of the registrant or an authorized operator. 10. Structural shielding requirements (see appendix C).