Mich. Admin. Code R. 333.5411 - X-ray equipment
Rule 411.
(1)
All x-ray tube housings in fixed fluoroscopic installations shall be of the
diagnostic type.
(2) The aluminum
equivalent of the total filtration permanently in the useful beam shall not be
less than 2.5 millimeters aluminum.
(3) The source-patient distance on
fluoroscopic machines should not be less than 45 centimeters (18 inches) and
shall not be less than 30 centimeters (12 inches).
(4) Provision shall be made to intercept the
scattered x-rays from the undersurface of the table top and other structures
under the fluoroscopic table if the tube is mounted under the table. A cone or
shield shall provide the same degree of attenuation as is required of the tube
housing.
(5) A shielding device of
at least 0.25 millimeter lead equivalence for covering the bucky slot during
fluoroscopy shall be provided.
(6)
A shielding device of at least 0.25 millimeter lead equivalence, such as
overlapping protective drapes or hinged or sliding panels, shall be used to
intercept scattered radiation that would otherwise reach the fluoroscopist and
others near the machine.
(7) A
fluoroscopic machine shall comply with both of the following:
(a) The entire cross section of the useful
beam shall be intercepted by the primary protective barrier of the fluoroscopic
image assembly at any SID. The fluoroscopic tube shall not produce x-rays
unless the barrier is in position to intercept the entire useful beam. The
exposure rate due to transmission through the barrier with the attenuation
block in the useful beam combined with radiation from the image intensifier, if
provided, shall not exceed 2 milliroentgens per hour at 10 centimeters from an
accessible surface of the fluoroscopic imaging assembly beyond the plane of the
image receptor for each roentgen per minute of entrance exposure
rate.
(b) The entrance exposure
rate shall be measured as described in subrule (15) of this rule. The exposure
rate due to transmission through the primary barrier combined with radiation
from the image intensifier shall be determined by measurements averaged over an
area of 100 square centimeters with no linear dimension greater than 20
centimeters. If the source is below the tabletop, the measurement shall be made
with the input surface of the fluoroscopic imaging assembly positioned 30
centimeters above the tabletop. If the source is above the tabletop and the SID
is variable, the measurement shall be made with the end of the beam-limiting
device or spacer as close to the tabletop as it can be placed, if it is not
closer than 30 centimeters. Movable grids and compression devices shall be
removed from the useful beam during the measurement. For all measurements, the
attenuation block shall be positioned in the useful beam 10 centimeters from
the point of measurement of the entrance exposure rate and between this point
and the input surface of the fluoroscopic imaging assembly.
(8) The lead equivalence of the
barrier of conventional fluoroscopes shall be not less than 1.5 millimeters at
100 kVp, 1.8 millimeters at 125 kVp, and 2.0 millimeters at potentials greater
than 125 kVp.
(9) A beam-limiting
device shall be provided to restrict the size of the useful beam to less than
the area of the barrier. The x-ray tube and beam-limiting system shall be
linked with the fluorescent screen assembly so that the useful beam at the
fluorescent screen is confined within the barrier irrespective of the
panel-screen distance. For image intensifiers, the useful beam shall be
centered on the input phosphor. It should not exceed the diameter of the input
phosphor during fluoroscopy or cine-recording. For spot film radiography with
image intensifier equipment, the shutters should automatically open to the
required field size before the exposure.
(10) Beam-limiting devices, such as
collimators, adjustable diaphragms, or shutters, shall provide the same degree
of attenuation as is required of the tube housing.
(11) A fluoroscopic machine shall comply with
either of the following:
(a) The x-ray field
produced by nonimage-intensified fluoroscopic equipment shall not extend beyond
the entire visible area of the image receptor. Means shall be provided to
permit further limitation of the field. The minimum field size at the greatest
SID shall be equal to or less than 5 by 5 centimeters.
(b) For image-intensified fluoroscopic
equipment, the total misalignment of the edges of the x-ray field with the
respective edges of the visible area of the image receptor along any dimension
of the visually defined field in the plane of the image receptor shall not
exceed 3% of the SID. The sum, without regard to sign, of the misalignment
along any 2 orthogonal dimensions intersecting at the center of the visible
area of the image receptor shall not exceed 4% of the SID. For rectangular
x-ray fields used with circular image receptors, the error in alignment shall
be determined along the length and width dimensions of the x-ray field which
pass through the center of the visible area of the image receptor. Means shall
be provided to permit further limitation of the field. The minimum field size,
at the greatest SID, shall be equal to or less than 5 by 5
centimeters.
(12) X-ray
production in the fluoroscopic mode shall be controlled by a device that
requires continuous pressure by the operator for the entire time of an
exposure. When recording serial fluoroscopic images, the operator shall be able
to terminate the x-ray exposures at any time, but means may be provided to
permit completion of any single exposure of the series in progress.
(13) When the fluoroscope is operated at 80
kVp, the exposure rate at the position where the beam enters the patient shall
not exceed 3.2 R/mA-min and should not exceed 2.1 R/mA-min.
(14) Entrance exposure rate limits for
fluoroscopic machines shall be as follows:
(a) Machines with automatic exposure rate
control shall not be operable at a combination of tube potential and current
which results in an exposure rate in excess of 10 roentgens per minute at the
point where the center of the useful beam enters the patient, except during
recording of fluoroscopic images or when an optional high level control is
provided. Special means of activation of high level controls, such as
additional pressure applied continuously by the operator, shall be required to
avoid accidental use. A continuous signal audible to the fluoroscopist shall
indicate that the high level control is being employed.
(b) Machines without automatic exposure rate
control shall not be operable at a combination of tube potential and current
which results in an exposure rate in excess of 5 roentgens per minute at the
point where the center of the useful beam enters the patient, except during
recording of fluoroscopic images or when an optional high level control is
activated. Special means of activation of high level controls, such as
additional pressure applied continuously by the operator, shall be provided to
avoid accidental use. A continuous signal audible to the fluoroscopist shall
indicate that the high level control is being employed.
(15) Compliance with subrule (14) of this
rule shall be determined as follows:
(a) If
the source is below the table, the exposure rate shall be measured 1 centimeter
above the tabletop or cradle.
(b)
If the source is above the table, the exposure rate shall be measured at 30
centimeters above the tabletop with the end of the beam-limiting device or
spacer positioned as closely as possible to the point of measurement.
(c) In a C-arm type of fluoroscope, the
exposure rate shall be measured 30 centimeters from the input surface of the
fluoroscopic imaging assembly.
(16) Means shall be provided to preset the
cumulative on-time of the fluoroscopic tube. The maximum cumulative time of the
timing device shall not exceed 5 minutes without resetting. A signal audible to
the fluoroscopist shall indicate the completion of the preset cumulative
on-time. This signal shall continue to sound while x-rays are produced until
the timing device is reset.
(17)
Devices which indicate the x-ray tube potential and current shall be provided.
On image intensified fluoroscopic equipment, these devices should be located in
such a manner that the operator may monitor the tube potential and current
during fluoroscopy.
Notes
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