| (C) The x-ray control panel shall provide visual indication
of the production of x-rays.
(D) The indicated technique factors shall be accurate
to meet manufacturer's specifications. If these specifications are
not available from the manufacturer, the factors shall be accurate
to within plus or minus 10% of the indicated setting.
(7) X-ray control. An x-ray control shall be incorporated
into each x-ray system such that an exposure can be terminated by
the operator at any time except for an exposure of 0.5 seconds or
less or during serial radiography when means shall be provided to
permit completion of any single exposure of the series in process.
(l) Additional machine requirements for x-ray systems.
This subsection does not apply to fluoroscopic or CT systems.
(1) Beam limitation. Beam limitation shall be as follows.
(A) Stationary general purpose x-ray systems.
(i) Beam-limiting devices shall restrict the useful
beam to the area of clinical interest as follows:
(I) the misalignment of the x-ray field for a manual
rectangular collimator shall be within plus or minus 2.0% of the SID
for the length or width of the image receptor;
(II) the x-ray field for a circular or polygon collimator
shall not exceed the diagonal of the image receptor by more than 2.0%
of the SID; or
(III) the misalignment of the x-ray field for an automatic
or semi-automatic collimator shall be within plus or minus 3.0% of
the SID for the length and width of the image receptor and shall be
within plus or minus 4.0% of the SID, without regard to the sign,
of the sum of the difference of the length and width of the image
receptor.
(ii) If the area of clinical interest is smaller than
the image receptor, the operator of the x-ray system shall use all
beam limiting devices necessary to restrict the useful beam to the
clinical area of interest.
(iii) A method shall be provided for visually defining
the perimeter of the x-ray field. The total misalignment of the edges
of the visually defined field with the respective edges, either the
length or width, of the x-ray field shall not exceed 2.0% of the SID.
(iv) A numerical SID indicator shall be present and
shall be accurate to within plus or minus 2.0% of the SID.
(v) The system shall indicate when the axis of the
x-ray field is perpendicular to the plane of the image receptor.
(vi) The center of the x-ray field, when perpendicular
to the image receptor, shall be accurate to within plus or minus 2.0%
of the SID with respect to the center of the image receptor.
(vii) The beam-limiting device shall numerically indicate
the field size in the plane of the image receptor.
(viii) Indication of field size dimensions and SIDs
shall be specified in inches and/or centimeters.
(ix) The field size indicated on the beam-limiting
device shall be within plus or minus 2.0% of the SID along the width
and length, separately, of the actual x-ray field size.
(B) Portable x-ray systems. Portable x-ray systems
shall comply with the requirements in subparagraph (A) of this paragraph,
as applicable, based on manufacturer's design.
(C) X-ray systems designed for one image receptor size.
X-ray systems designed for only one image receptor size at a fixed
SID shall provide a means to do the following:
(i) limit the x-ray field to no greater than the dimensions
of the image receptor at the SID, and to align the center of the x-ray
field with the center of the image receptor to within plus or minus
2.0% of the SID center; or
(ii) align the x-ray field such that the x-ray field
does not extend beyond any edge of the image receptor at the SID.
(D) Special purpose x-ray systems.
(i) When the x-ray beam is perpendicular to the plane
of the image receptor, a means shall be provided to do the following:
(I) limit the x-ray field such that the x-ray field
does not exceed each dimension of the image receptor by more than
2.0% of the SID; and
(II) align the center of the x-ray field with the center
of the image receptor to within plus or minus 2.0% of the SID.
(ii) The requirements of clause (i) of this subparagraph
may be met with a system that meets the requirements for a general
purpose x-ray system as specified in subparagraph (A)(i) - (iv) of
this paragraph or, when alignment means are also provided, may be
met with either of the following:
(I) an assortment of removable, fixed-aperture, beam-limiting
devices sufficient to meet the requirement for each combination of
image receptor size and SID for which the unit is designed with each
such device having clear and permanent markings to indicate the image
receptor size and SID for which it is designed; or
(II) a beam-limiting device having multiple fixed apertures
sufficient to meet the requirement for each combination of image receptor
size and SID for which the radiation machine is designed. Permanent,
clearly legible markings shall indicate the image receptor size and
SID for which each aperture is designed and shall indicate which aperture
is in position for use.
(2) Radiation exposure control devices. Radiation exposure
control devices shall include the following:
(A) Timers. Means shall 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, 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) AEC. When AEC is provided, the following shall
occur.
(i) Indication shall be made on the control panel when
AEC mode of operation is selected.
(ii) If the x-ray tube potential is equal to or greater
than 50 kVp, the minimum exposure time for field emission equipment
rated for pulsed operation shall be equal to or less than a time interval
equivalent to 2 pulses.
(iii) The minimum exposure time for all x-ray systems
other than that specified in clause (ii) of this subparagraph shall
be equal to or less than 0.0167 second or a time interval required
to deliver 5 mAs, whichever is greater.
(iv) A visible and/or audible signal shall indicate
when an exposure has been terminated.
(C) Exposure interval reproducibility. When all technique
factors are held constant, including control panel selections associated
with AEC systems, the coefficient of variation of exposure interval
for both manual and AEC systems shall not exceed 0.05. This requirement
applies to clinically used techniques.
(3) SSD. All portable x-ray systems shall be provided
with means to limit the SSD to equal to or greater than 30 cm.
(4) Exposure reproducibility. When all technique factors
are held constant, including control panel selections associated with
AEC systems, the coefficient of variation of exposure for both manual
and AEC systems shall not exceed 0.05. This requirement applies to
clinically used techniques.
(5) Linearity. The average ratios of exposure (air
kerma) mR/mGy to the indicated mAs product obtained at any 2 consecutive
mA or mAs settings shall not differ by more than 0.10 times their
sum, where X1 and X2 are
the average mR/mAs (mGy/mAs) values obtained at each of 2 consecutive
tube current settings:
Attached Graphic
(6) Radiation from capacitor. Radiation from capacitor
energy storage equipment in standby status. Radiation emitted from
the x-ray tube when the exposure switch or timer is not activated
shall not exceed a rate of 2 milliroentgens per hour (mR/hr) or 0.02
milligray per hour (mGy/hr) at 5 cm from any accessible surface of
the diagnostic source assembly, with the beam-limiting device fully
open.
(7) X-ray systems needing correction or repair. In
order to achieve compliance with this chapter, the correction or repair
shall begin within 30 days following the failure and shall be performed
according to a plan designated by the registrant. Correction or repair
shall be completed no longer than 90 days from discovery unless authorized
by the agency.
(8) Records of an x-ray system corrections or repairs.
The registrant shall maintain records of corrections or repairs and
any tests, measurements or numerical readings listed in subsection
(o)(6) of this section in accordance with subsection (s)(1) of this
section for inspection by the agency.
(m) Fluoroscopic systems and spot-film devices for
all facilities.
(1) Limitation of the useful beam. Limitation of the
useful beam shall be as follows.
(A) Primary barrier.
Cont'd... |
