32 Ill. Adm. Code 370.110
Equipment Quality Assurance Tests
Section 370
Section 370.110 Equipment
Quality Assurance Tests
a) Daily quality control tests. Film processors used to develop
mammograms shall be adjusted and maintained to meet the technical development
specifications for the mammography film in use. A processor performance test
shall be performed on each day that examinations are performed before any
clinical films are processed that day. The test shall include an assessment of
base plus fog density, mid-density and density difference, using the
mammography film used clinically at the facility.
1) The base plus fog density shall be within plus 0.03 of the
established operating level.
2) The mid-density shall be within plus or minus 0.15 of the
established operating level.
3) The density difference shall be within plus or minus 0.15 of
the established operating level.
b) Weekly quality control tests. Facilities with screen-film
systems shall perform a phantom image quality evaluation test at least weekly,
using the Mammography Image Evaluation Protocol found in Appendix B of this
Part.
1) The optical density of the film at the center of an image of
the phantom shall be at least 1.20 when exposed under a typical clinical
condition.
2) The optical density of the film at the center of the phantom
image shall not change by more than plus or minus 0.20 from the established
operating level.
3) The mammography system shall be capable of producing images of
the mammography phantom in which the following objects are visualized:
A) The three largest masses with thicknesses of 2.0, 1.0 and 0.75
millimeter.
B) The three largest speck groups with diameters of 0.54, 0.40 and
0.32 millimeter.
C) The four largest fibers with thicknesses of 1.56, 1.12, 0.89
and 0.75 millimeter.
4) The density difference between the background of the phantom
and an added test object, used to assess image contrast, shall be measured and
shall not vary by more than plus or minus 0.05 from the established operating
level.
c) Quarterly quality control tests. Facilities with screen-film
systems shall perform the following quality control tests at least quarterly:
1) Fixer retention in film. The residual fixer shall be no more
than 5 micrograms per square cm.
2) Repeat analysis. If the total repeat or reject rate changes
from the previously determined rate by more than 2.0 percent of the total films
included in the analysis, the reasons for the change shall be determined. Any
corrective actions shall be recorded and the results of these corrective
actions shall be assessed.
d) Semiannual quality control tests. Facilities with screen-film
systems shall perform the following quality control tests at least
semiannually:
1) Darkroom fog. The optical density attributable to darkroom
fog shall not exceed 0.05 when a mammography film of the type used in the
facility, which has a mid-density of no less than 1.20, is exposed to typical
darkroom conditions for 2 minutes while such film is placed on the counter top
emulsion side up. If the darkroom has a safelight used for mammography film, it
shall be on during this test.
2) Screen-film contact. Testing for screen-film contact shall be
conducted using 40 mesh copper screen. All cassettes used in the facility for
mammography shall be tested.
3) Compression device performance. The compression device
performance shall:
A) Be capable of maintaining a compression force of at least 111
newtons (25 pounds) for at least 15 seconds;
B) Not be capable of exceeding a compression force of more than
209 newtons (47 pounds) when used in an automatic or power drive mode.
e) Annual quality control tests. Facilities with screen-film
systems shall perform the following quality control tests at least annually:
1) Automatic exposure control performance.
A) The AEC shall be capable of maintaining film optical density
within plus or minus 0.30 of the mean optical density when thickness of a
homogeneous material is varied over a range of 2 to 6 cm and the kVp is varied
appropriately for such thicknesses over the kVp range used clinically in the
facility. If this requirement cannot be met, a technique chart shall be
developed showing appropriate techniques (kVp and density control settings) for
different breast thicknesses and compositions that shall be used so that
optical densities within plus or minus 0.30 of the average under phototimed
conditions can be produced.
B) The AEC shall be capable of maintaining film optical density
within plus or minus 0.15 of the mean optical density when thickness of a
homogeneous material is varied over a range of 2 to 6 cm and the kVp is varied
appropriately for such thicknesses over the kVp range used clinically in the
facility.
C) The optical density of the film in the center of the phantom
image shall not be less than 1.20.
2) Kilovoltage peak accuracy and reproducibility. The kVp shall
be accurate within plus or minus 5 percent of the indicated or selected kVp at:
A) The lowest clinical kVp that can be measured by a kVp test
device;
B) The most commonly used clinical kVp;
C) The highest available clinical kVp; and
D) At the most commonly used clinical settings of kVp, the
coefficient of variation of reproducibility of the kVp shall be equal to or
less than 0.02.
3) Focal spot dimensions. Facilities shall evaluate focal spot
condition by determining the system resolution. For focal spot dimensions, the
measured values of the focal spot length (dimension parallel to the anode
cathode axis) and width (dimension perpendicular to the anode-cathode axis)
shall be within the tolerance limits specified in this subsection (e)(3).
Focal
Spot Tolerance Limit
Nominal Focal
Maximum Measured Dimensions
Spot Size
(mm)
Width (mm)
Length (mm)
0.10
0.15
0.15
0.15
0.23
0.23
0.20
0.30
0.30
0.30
0.45
0.65
0.40
0.60
0.85
0.60
0.90
1.30
4) System resolution. Facilities shall evaluate focal spot
condition by determining the system resolution as follows:
A) Each x-ray system used for mammography, in combination with the
mammography screen-film combination used in the facility, shall provide a
minimum resolution of 11 cycles/millimeter (mm) (line-pairs/mm) when a high
contrast resolution bar test pattern is oriented with the bars perpendicular to
the anode-cathode axis, and a minimum resolution of 13 line-pairs/mm when the
bars are parallel to that axis.
B) The bar pattern shall be placed 4.5 cm above the breast support
surface, centered with respect to the chest wall edge of the image receptor,
and with the edge of the pattern within 1 cm of the chest wall edge of the
image receptor.
C) When more than one target material is provided, the measurement
shall be made using the appropriate focal spot for each target material.
D) When more than one source-image receptor distance is provided,
the test shall be performed at SID most commonly used clinically.
E) Test kVp shall be set at the value used clinically by the
facility for a standard breast and shall be performed in the AEC mode, if
available. If necessary, a suitable absorber may be placed in the beam to
increase exposure times. The screen-film cassette combination used by the
facility shall be used to test for this requirement and shall be placed in the
normal location used for clinical procedures.
5) Beam quality and half-value layer (HVL). For mammography
systems operating at x-ray tube potentials of less than 50 kVp, the HVL in
millimeters of aluminum of the useful beam shall be equal to or greater than
the product of the measured tube potential in kilivolts multiplied by 0.01.
The half-value layer shall be measured with the compression device in the beam
and shall be measured at the same tube potential used in Appendix A of this
Part, Mammography Dose Measurement Protocol, and Appendix B of this Part,
Mammography Phantom Image Evaluation.
AGENCY NOTE: If the measured half-value layer is
significantly greater than the specified minimum, image contrast will be
reduced and overall image quality will be degraded. For screen-film
mammography systems, it is recommended that the HVL not exceed the minimum
acceptable HVL by more than 0.1 millimeter of aluminum, as specified in the
Mammography Quality Control Manual: Medical Physicist's Section, Revised
Edition, 1999.
6) Breast entrance air kerma and AEC reproducibility. The
coefficient of variation for both air kerma and mAs shall not exceed 0.05.
7) Dosimetry. The average glandular dose delivered during a
single craniocaudal view of a phantom simulating a standard breast shall not
exceed 3.0 milligray (mGy) (0.3 rad) per exposure. The dose shall be
determined with technique factors and conditions used clinically for a standard
breast (see Appendix A of this Part).
8) X-ray field/light field/image receptor/compression paddle
alignment.
A) All systems shall have beam-limiting devices that allow the
entire chest wall edge of the x-ray field to extend to the chest wall edge of
the image receptor and provide means to assure that the x-ray field does not
extend beyond any edge of the image receptor by more than 2 percent of the SID.
B) If a light field that passes through the x-ray beam limitation
device is provided, it shall be aligned with the x-ray field so that the total
of any misalignment of the edges of the light field and the x-ray field along
either the length or the width of the visually defined field at the plane of
the breast support surface shall not exceed 2 percent of the SID.
C) The chest wall edge of the compression paddle shall not extend
beyond the chest wall edge of the image receptor by more than one percent of
the SID when tested with the compression paddle placed above the breast support
surface at a distance equivalent to standard breast thickness. The shadow of
the vertical edge of the compression paddle shall not be visible on the image.
9) Uniformity of screen speed. Uniformity of screen speed of all
the cassettes in the facility shall be tested and the difference between the
maximum and minimum optical densities shall not exceed 0.30. Screen artifacts
shall also be evaluated during this test.
10) System artifacts. System artifacts shall be evaluated with a
high-grade, defect-free sheet of homogeneous material large enough to cover the
mammography cassette and shall be performed for all cassette sizes used in the
facility using a grid appropriate for the cassette size being tested. System
artifacts shall also be evaluated for all available focal spot sizes and target
filter combinations used clinically.
11) Radiation output.
A) The system shall be capable of producing a minimum output of
4.5 mGy air kerma per second (513 mR per second) when operating at 28 kVp in
the standard mammography (moly/moly) mode at any SID where the system is
designed to operate and when measured by a detector with its center located 4.5
cm above the breast support surface with the compression paddle in place
between the source and the detector. The system, under the same measuring
conditions, shall be capable of producing a minimum output of 7.0 mGy air kerma
per second (800 mR per second) when operating at 28 kVp in the standard
(moly/moly) mammography mode at any SID where the system is designed to
operate.
B) The system shall be capable of maintaining the required minimum
radiation output averaged over a 3.0 second period.
12) Decompression. If the system is equipped with a provision
for automatic decompression after completion of an exposure or interruption of
power to the system, the system shall be tested to confirm that it provides:
A) An override capability to allow maintenance of compression;
B) A continuous display of the override status; and
C) A manual emergency compression release that can be activated in
the event of power or automatic release failure.
f) Quality control tests-other modalities. For systems with
image receptor modalities other than screen-film, the quality assurance program
shall be substantially the same as the quality assurance program recommended by
the image receptor manufacturer, except that the maximum allowable dose shall
not exceed the maximum allowable dose for screen-film systems in subsection
(e)(7) of this Section.
g) Mobile units. The facility shall verify that mammography
units used to produce mammograms at more than one location meet the requirements
in subsections (a) through (f) of this Section. In addition, at each
examination location, before any examinations are conducted, mobile mammography
systems shall be tested using the mammography phantom image evaluation, or
shall meet the following requirements:
1) A medical physicist shall establish a protocol for measurement
of the radiation output of the mammography system, including the radiation
measuring device to be used, procedures for performing the measurement and the
anticipated result of the measurement.
2) Measurements shall be performed using the technique factors
that were used for the most recent phantom image evaluation. If a change is
made in the technique factors used for the measurements required in this
subsection (g)(2), the image quality shall be tested using the mammography
phantom image evaluation protocol found in Appendix B of this Part.
AGENCY NOTE:
If the phantom image evaluation is performed using a phototimer, the medical
physicist may specify appropriate technique factors that approximate those used
by the phototimer for the measurements required in this Section.
3) After each relocation of a mobile mammography system,
measurements of the radiation output of the machine shall be performed
according to the protocol established in this Section.
4) If the radiation output measurement exceeds plus or minus 15
percent of the value established by the medical physicist, the system shall not
be used to image human patients until the cause for the variation has been
investigated and corrected.
5) Records of radiation output measurements for mobile
mammography systems shall be maintained at the location of the mammography
system for a period of not less than one inspection cycle.
AGENCY NOTE:
The Agency recommends that mobile mammography systems be tested for image
quality after each relocation and prior to use on patients, with mammography
phantom image evaluation protocol in Appendix B of this Part.
h) Use of test results.
1) After completion of the tests specified in subsections (a) through
(g) of this Section, the facility shall compare the test results to the
corresponding specified action limits, or for nonscreen-film modalities, to the
manufacturer's recommended action limits, or for post-move, preexamination
testing of mobile units, to the limits established in the test method used by
the facility.
2) If the test results fall outside of the action limits, the
source of the problem shall be identified and corrective actions shall be
taken:
A) Before any further examinations are performed or any films are
processed using the component of the mammography system that failed the test,
if the failed test was that described in subsection (a), (b), (d)(1), (d)(2),
(d)(3), (e)(7), (f) or (g) of this Section;
B) Within 30 days after the test date for all other tests
described in this Section.
i) Surveys.
1) At least once a year, each facility shall undergo a survey by
a medical physicist or by an individual under the direct supervision of a
medical physicist. At a minimum, this survey shall include the performance of
tests to ensure that the facility meets the quality assurance requirements of
the annual tests described in subsections (e) and (f) of this Section and the
weekly phantom image quality test described in subsection (b) of this Section.
2) Calibration of air kerma measuring instruments. Instruments
used by medical physicists in their annual survey to measure the air kerma or
air kerma rate from a mammography unit shall be calibrated at least once every
2 years and each time the instrument is repaired. The instrument calibration
shall be traceable to a national standard and calibrated with an accuracy of
plus or minus 6 percent (95 percent confidence level) in the mammography energy
range.
3) The results of all tests conducted by the facility in
accordance with subsections (a) through (g) of this Section, as well as written
documentation of any corrective actions taken and their results, shall be
evaluated for adequacy by the medical physicist performing the survey.
4) The medical physicist shall prepare a survey report that
includes a summary of this review and recommendations for necessary
improvements.
5) The survey report shall be sent to the facility within 30 days
after the date of the survey.
6) The survey report shall be dated and signed by the medical
physicist performing or supervising the survey. If the survey was performed
entirely or in part by another individual under the direct supervision of the
medical physicist, that individual and the part of the survey that individual
performed shall also be identified in the survey report.
j) Mammography equipment evaluations. Additional evaluations of
mammography units or image processors shall be conducted whenever a new unit or
processor is installed, a unit or processor is dissembled and reassembled at
the same or a new location, or major components of a mammography unit or
processor equipment are changed or repaired. These evaluations shall be used
to determine whether the new or changed equipment meets the requirements of
applicable standards in this Section and Section 370.80 of this Part. All
problems shall be corrected before the new or changed equipment is put into
service for examinations or film processing. The mammography equipment
evaluation shall be performed by a medical physicist or by an individual under
the direct supervision of a medical physicist.