Current through 2024-38, September 18, 2024
In addition to the provisions of F.3, F.4, and F.5, the
requirements of F.8 apply to x-ray equipment and associated facilities used for
dental radiography. Requirements for extraoral dental radiographic systems are
covered in F.7.
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, i.e., SSD, to not less
than:
(1) 18 centimeters if operable above 50
kVp, or
(2) 10 centimeters if
operable at 50 kVp.
B.
Field Limitation. Radiographic systems designed for use with an intraoral image
receptor shall be provided with means to limit the x-ray beam such that:
(1) If the minimum SSD is 18 centimeters or
more, the x-ray field at the minimum SSD shall be containable in a circle
having a diameter of no more than 7 centimeters; and
(2) If the minimum SSD is less than 18
centimeters, the x-ray field at the minimum SSD shall be containable in a
circle having a diameter of no more than 6 centimeters.
C. Radiation exposure control for certified
and non-certified systems.
(1) Exposure
Initiation
(a) 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
(b) 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.
(2) Exposure
termination
(a) 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.
(b) 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.
(c) Termination of
an exposure shall cause automatic resetting of the timer to its initial setting
or to zero
(3) 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.
(4) 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 percent of the average exposure
time (T), when four timing tests are performed:
(Tmax - Tmin) < 0.10T
D. X-Ray control.
(1) Each x-ray control shall be located in
such a way as to meet the following requirements:
(a) Stationary x-ray systems shall be
required to have the x-ray control permanently mounted in a protected area, and
the operator is required to remain in that protected area, or six feet away and
out of the useful beam during the entire exposure; and
(b) 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
F.8.D(1)(a);
(ii) Used for greater
than one hour and less than one week at the same location, i.e., a room or
suite, shall meet the requirements of F.8.D(1)(b)(i) or be provided with a 6.5
(1.98m) foot high protective barrier which is placed at least 6 feet (1.98m)
from the tube housing assembly and at least 6 feet (1.98m) from the patient;
or
(iii) Used to make an
exposure(s) of a patient at the use location shall meet the requirement of
F.8.D(2)(b)(i) or (ii) or be provided with a method of x-ray control which will
permit the operator to be at least 6 feet (3.66m) from the tube housing
assembly and out of the useful beam during an exposure.
(2) 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, if available to the unit, shall indicate that the exposure has
terminated.
E. Exposure
reproducibility. The coefficient of variation shall not exceed 0.10 when all
technique factors are held constant. This requirement shall be deemed to have
been met if, when 4 exposures are made at identical
technique factors, that the value of the average
exposure (E) is greater than or equal to 5 times the
maximum exposure (Emax), minus the minimum
exposure (Emin): i.e., E > 5(Emax- Emin).
F. Administrative controls.
(1) Patient and film holding devices shall be
used when the techniques permit.
(2) The tube housing and the PID shall not be
hand-held during an exposure.
(3)
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 F.8.B.(1).
(4) Dental fluoroscopy without image
intensification shall not be used.
G. Additional requirements Applicable to
certified systems only. Only diagnostic x-ray systems incorporating one or more
certified component(s) shall be required to comply with the following
additional requirements(s) which relate to that certified component(s).
(1) 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 0.05, for any
specific combination of selected technique factors.
(2) 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 the requirements of applicable
Federal standards, for any fixed x-ray tube potential within the range of 40
percent to 100 percent of the maximum rating, the average ratios of
exposure to the indicated milliampere-seconds product,
obtained at any two consecutive tube current settings shall not differ by more
than 0.10 times their sum,
i.e., X1-X2 < 0.10 (X1 + X2),
where X1 and X2 are the average mR/mAs values obtained at
each of two consecutive tube current settings.
(3) Accuracy. Deviation of technique factors
from indicated values shall not exceed the limits specified for that system by
its manufacturer. In the absence of the manufacturer's specifications the
deviation shall not exceed 10 percent of the indicated value.
(4) Timers. Termination of exposure shall
cause automatic resetting of the timer to its initial setting or to
zero.
(5) Beam quality. All
certified dental x-ray systems manufactured on or after December 1, 1980, shall
have a minimum half-value layer not less than 1.5 millimeters aluminum
equivalent. Systems operating above 70 kVp are subject to the filtration
requirements of F.5.E.(1).
