Section 157.78. Intraoral dental radiographic systems.

 

(1)   General. In addition to the provisions of ss. DHS 157.74 and 157.75 , the requirements in this section apply to x-ray equipment and associated facilities used for dental radiography. Requirements for extraoral dental radiographic systems are contained in s. DHS 157.77 .

(2)   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 either one of the following:

(a) 20 centimeters (8 inches) if operable above 50 kVp. Beam-limiting devices shall be lead lined.

(b) 10 centimeters (4 inches) if operable at 50 kVp only. Beam-limiting devices shall be lead lined.

(3)   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 the beam at the minimum SSD shall be contained in a circle having a diameter of no more than 7 centimeters.

(4)   Radiation exposure control. Intraoral radiographic systems shall meet all of the following exposure control requirements:

(a) Exposure initiation. 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 may not be initiated without such an action. An exposure may not be made 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 exposure 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. 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. Termination of an exposure shall cause automatic resetting of the timer to its initial setting or to "zero" except for panoramic systems that may pause during the exposure cycle.

(d) Exposure control location and operator protection. An x-ray system shall meet all the following requirements, as applicable, to ensure operator protection during use of the system:

1. A stationary x-ray system shall have an x-ray exposure control that may be moved to a protected area so that the operator is required to remain in that protected area during the entire exposure. The exposure cord shall be of sufficient length to allow the operator to be at least 2 meters (6.5 feet) from the x-ray tube head and not in the direction the tube is pointed. The operator shall be able to determine when the exposure has completed either by audible tone or by visible signal.

2. A mobile or portable x-ray system that is used for greater than one week in the same location, which is a room or suite, shall meet the requirements of stationary dental equipment.

3. A mobile or portable x-ray system that is used for less than one week in the same location shall be provided with either a protective barrier at least 2 meters (6.5 feet) high for operator protection or means to allow the operator to be at least 2 meters (6.5 feet) from the tube housing assembly while making exposures.

(5)   Reproducibility. When the equipment is operated on an adequate power supply as specified by the manufacturer, the estimated coefficient of variation of air kerma may be no greater than 0.05 for any specific combination of selected technique factors.

(6)   m A/ m As linearity. X-ray equipment that is operated on a power supply as specified by the manufacturer for any fixed x-ray tube potential within the range of 40% to 100% of the maximum rated shall meet all of the following requirements:

(a) Equipment having independent selection of x-ray tube current. The average ratios of air kerma to the indicated milliampere-seconds product, in units of .001 mGy/mAs (mR/mAs), obtained at any 2 consecutive tube current settings may not differ by more than 0.10 times their sum:

X 1 - X 2 < 0.10 (X 1 +X 2 )

where X 1 and X 2 are the average values obtained at each of 2 consecutive tube current settings, or at 2 settings differing by no more than a factor of 2 where the tube current selection is continuous.

(b) Equipment having a combined x-ray tube current-exposure time product selector but not a separate tube current selector. The average ratios of air kerma to the indicated milliampere-seconds product, in units of .001 mGy/mAs (mR/mAs), obtained at any 2 consecutive mAs selector settings may not differ by more than 0.10 times their sum:

X 1 - X 2 < 0.10 (X 1 +X 2 )

where X 1 and X 2 are the average values obtained at any 2 consecutive mAs selector settings, or at 2 settings differing by no more than a factor of 2 where the mAs selector provides continuous selection.

(c) Measuring compliance. Determination of compliance shall be based on 10 exposures taken within a time period of one hour at each of the 2 settings. The 2 settings may include any 2 focal spot sizes except where one is equal to or less than 0.45 millimeters and the other is greater than 0.45 millimeters. For purposes of this requirement, focal spot size is the nominal focal spot size specified by an x-ray tube manufacturer.

(7)   Accuracy. Deviation of technique factors from indicated values for kVp and exposure time, if time is independently selectable, may not exceed the limits specified for that system by its manufacturer. In the absence of manufacturer's specifications the deviation may not exceed 10% of the indicated value for kVp and 10% for time.

(8)   Kvp limitations. Dental x-ray machines with a nominal fixed kVp of less than 50 kVp may not be used to make diagnostic dental radiographs of humans.

(9)   Administrative controls.

(a) Intraoral film holding devices shall be used.

(b) The tube housing and the cone may not be hand-held during an exposure.

(c) The tube shall be stationary during exposure, except for panoramic systems. Any oscillation of the tube head shall cease before exposure is made.

CR 01-108 : cr. Register July 2002 No. 559 , eff. 8-1-02.