Current through Register Vol. 46, No. 15, April 8, 2022
In addition to the provisions of Sections 360.10, 360.30,
360.40 and 360.41 of this Part, the requirements of this Section apply to x-ray
equipment and associated facilities used in the healing arts of medicine,
chiropractic and podiatry. It does not apply to fluoroscopic, dental,
veterinary or computed tomography systems.
a) Beam Limitation. The useful beam shall be
limited to the area of clinical interest.
1)
Stationary General Purpose and Mobile/Portable X-Ray Systems
A) Variable X-Ray Field Limitation. An
adjustable collimator shall be provided with means for independent stepless
adjustment of the size of the x-ray field.
B) Visual Indication of Field Size. Means
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 respect to
the edges of the x-ray field, along either the length or the width of the
visually defined field, shall not exceed two percent of the distance from the
source to the center of the visually defined field when the surface upon which
it appears is perpendicular to the axis of the x-ray beam.
AGENCY NOTE: When a light localizer is used to define the x-ray
field, it should provide an average illumination of not less than 100 lux (9
footcandles) at 100 centimeters or at the maximum SID, whichever is
less.
2) Special
Purpose X-Ray Systems
A) Means shall be
provided to limit the x-ray field in the plane of the image receptor so that
such field does not exceed each dimension of the image receptor by more than
two percent of the SID when the axis of the x-ray beam is perpendicular to the
plane of the image receptor.
B) The
requirements of subsection (a)(2)(A) of this Section may be met:
i) With a system that meets the requirements
specified in subsection (a)(1) of this Section; or
ii) With 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 used,
with each such device having permanent, clearly legible markings, in
centimeters and/or inches, to indicate the image receptor size and SID for
which it is designed; or
iii) With
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
unit is used. Permanent, clearly legible markings, in centimeters and/or
inches, shall indicate the image receptor size and SID for which each aperture
is designed and shall indicate which aperture is in position for use.
3) Radiation therapy
simulation systems shall be exempt from the beam limitation requirements of
this Section.
b)
Radiation Exposure Control Devices
1) Timers.
Means shall be provided to terminate the exposure at a preset time interval,
preset product of current and time, preset number of pulses or preset radiation
exposure to the image receptor. Also, 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) X-Ray Control
A) 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:
i) Exposures of 0.5
second or less; or
ii) During
serial radiography when means shall be provided to permit completion of any
single exposure of the series in process.
B) The exposure switch shall be a dead-man
switch.
3) Automatic
Exposure Controls (AEC). Systems which are provided with automatic exposure
control devices shall incorporate a back-up timer to terminate the radiation
exposure in the event of AEC failure. In addition, they shall meet the
following requirements:
A) Indication shall be
made on the control panel when this mode of operation is selected;
and
B) A visible signal shall
indicate when an exposure has been terminated by the back-up timer, and manual
resetting shall be required before further automatically timed exposures can be
made.
c)
Source-Skin Distance (SSD). All mobile or portable radiographic systems shall
be provided with means to limit the SSD to 30 centimeters or greater.
d) Linearity. For equipment that is operated
at more than one x-ray tube current or current-time product setting, the
average ratios of exposure (microcoulombs per kilogram or milliroentgens) to
the indicated milliampere-seconds (mAs) product obtained at any two tube
current or current-time product settings utilized shall not differ by more than
0.10 times their sum. This requirement is mathematically represented by the
following:
[ Image][LESS THAN
OR EQUAL TO][ Image]
where
Image
and Image are the
average microC/kg/mAs or mR/mAs values obtained at any two tube current or
current-time product settings utilized. Compliance shall be determined at any
fixed x-ray tube potential within the rage of 40 percent to 100 percent of the
maximum rated tube potential.
e) Medical Radiographic Entrance Exposure
Limits. The in-air exposure determined for the technique used for the specified
average adult patient for routine medical radiography shall not exceed the
entrance exposure limits shown below: (See Section 360.Appendix A of this Part
for measurement protocol and calculation of exposure at skin entrance.)
|
Technique
|
Thickness (cm)
|
Exposure Limit (microC/kg)
|
(mR)
|
|
Chest (PA), Grid
|
23
|
9
|
35
|
|
Chest (PA), Non-Grid
|
23
|
8
|
30
|
|
Abdomen (KUB)
|
23
|
155
|
600
|
|
Lumbo-Sacral Spine (AP)
|
23
|
206
|
800
|
|
Cervical Spine (AP)
|
13
|
52
|
200
|
|
Skull (lateral)
|
15
|
65
|
250
|
|
Foot (D/P)
|
8
|
26
|
100
|
AGENCY NOTE: These exposures are maximums. With careful
selection of technique factors, adjustment of film processing systems, and
choice of film and screen-film combinations, patient exposures can be further
reduced.
f) SID Indication
1) Means shall be provided to indicate the
SID.
2) SIDs shall be indicated in
centimeters and/or inches and the measured SID shall correspond to the
indicated value to within two percent.
g) X-Ray Field/Image Receptor Alignment.
Means shall be provided to:
1) Indicate when
the axis of the x-ray field is perpendicular to the plane of the image
receptor; and
2) Align the center
of the x-ray field with respect to the center of the image receptor to within
two percent of the SID.
