| (13) Gonadal shielding. Gonadal shielding shall be
used on patients when the gonads are in or within 5 cm of the useful
beam. This requirement does not apply if the shielding will interfere
with the diagnostic procedure. Gonadal shielding shall be of at least
0.5 mm lead equivalent material.
(14) Measurements of the radiation output for x-ray,
fluoroscopic, and CT systems. Measurements of the radiation output
of x-ray, fluoroscopic, and CT systems shall be performed with a calibrated
dosimetry system in accordance with the following.
(A) The dosimetry system calibration shall be traceable
to a national standard.
(B) Dosimetry systems shall be calibrated within 24
months from the date of the prior calibration.
(C) Measurements of radiation output shall be performed
with a dosimetry system that has been calibrated within the 24 months
preceding the date of the measurement.
(D) Record of the dosimetry system calibration shall
include:
(i) manufacturer's name, model and serial number of
each calibrated instrument;
(ii) date of the calibration; and
(iii) name of the individual recording the information.
(E) The registrant shall record the dosimetry system
calibration information specified in subparagraph (D)(i) - (iii) of
this paragraph and maintain that record in accordance with subsection
(s)(1) of this section for inspection by the agency.
(j) Radiographic entrance exposure (air kerma) limits.
The in-air exposure (air kerma) determined for the technique used
by the registrant for the specified average human adult patient thickness
for medical radiography shall not exceed the entrance exposure (air
kerma) limits in the following Table I.
Attached Graphic
(k) Machine requirements for general x-ray and fluoroscopic
systems.
(1) Warning label. The warning label will meet the
requirements of §289.231(z) of this title.
(2) Mechanical support of tube head. The tube housing
assembly shall be adjusted to remain stable during an exposure unless
tube housing movement is a designed function of the x-ray system.
(3) Battery charge indicator. On battery-powered x-ray
generators, visual means shall be provided on the control panel to
indicate whether the battery is in a state of charge adequate for
proper operation.
(4) Beam quality. The following requirements apply
to beam quality.
(A) Half-value layer.
(i) The half-value layer of the useful beam for a given
x-ray tube potential shall not be less than the values shown in the
following Table II. If it is necessary to determine such half-value
layer at an x-ray tube potential that is not listed in Table II, linear
interpolation may be made.
Attached Graphic
(ii) For capacitor energy storage equipment, compliance
with the requirements of this paragraph shall be determined with the
maximum quantity of charge per exposure.
(B) Filtration controls.
(i) For x-ray systems that have variable kVp and variable
filtration for the useful beam, a device shall link the kVp selector
with the filters and shall prevent an exposure unless the minimum
amount of filtration required by subparagraph (A) of this paragraph
is in the useful beam for the given kVp that has been selected.
(ii) Any other system having removable filters shall
be required to have the minimum amount of filtration as required by
subparagraph (A)(i) of this paragraph permanently located in the useful
beam during each exposure.
(5) Multiple tubes. Where two or more radiographic
tubes are controlled by one exposure switch, the tube or tubes that
have been selected shall be clearly indicated prior to initiation
of the exposure. This indication shall be both on the x-ray control
panel and at or near the tube housing assembly that has been selected.
(6) Technique and exposure indicators.
(A) The technique factors to be used during an exposure
shall be indicated before the exposure begins except when automatic
exposure controls are used, in which case the technique factors that
are set prior to the exposure shall be indicated.
(B) On x-ray systems having fixed technique factors,
the requirement of subparagraph (A) of this paragraph may be met by
permanent markings.
(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.
Cont'd... |
