Phantom Image - Weekly Equipment Quality Control Tests
Citation:
900.12(e)(2)(i),(ii),(iii),(iv): (2) Weekly quality
control tests. Facilities with screen-film systems shall perform an image
quality evaluation test, using an FDA-approved phantom, at least weekly.
(i) The
optical density of the film at the center of an image of a standard FDA-accepted
phantom shall be at least 1.20 when exposed under a typical clinical condition.
(ii) The
optical density of the film at the center of the phantom image shall not
change by more than ±0.20 from the established operating level.
(iii) The
phantom image shall achieve at least the minimum score established by
the accreditation body and accepted by FDA in accordance with 900.3(d)
or 900.4(a)(8).
(iv) 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 ±0.05 from the established operating level.
Approved Alternative Standards:
Daily Processor QC Tests
Weekly
Phantom Image Test
Questions:
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The
regulations specify a minimum optical density of 1.2 at the center
of the phantom image when exposed under typical clinical conditions.
Is there an upper limit on this density and why does it have to be
measured in the center of the phantom?
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What
is an acceptable documentation for the phantom image QC? Is a table
of values sufficient or should the facility plot the results?
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A
facility is using more than one type of screen-film combination. Must
it perform the QC tests separately for each combination used?
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Under
what circumstances should I establish a new baseline optical density
(OD) operating level?
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Should
artifacts be subtracted during the evaluation of the weekly phantom
QC test and should the fibers, speck groups and masses be charted
separately?
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Under
the regulations can the “added” test object used to perform the image
contrast test be placed in positions other than on top of the phantom?
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If
a weekly QC test is performed every week but not every 7 days, can
the facility be cited?
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When
performing the weekly phantom QC test, should we use film from the
box currently being used to produce clinical exams or film from the
box used for quality control purposes?
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When
evaluating the phantom QC test, must the technologist and the physicist
adjust the phantom scoring for artifacts?
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We
perform our weekly phantom images using an AEC mode different from
the Full-Auto AEC mode that we typically use for patients. Is this
acceptable toward meeting the requirement?
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When
performing the weekly phantom image test must we monitor kVp and/or
mAs?
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If
the optical density (OD) for the weekly phantom test falls below 1.20
(and/or changes by more than +/- 0.20 from the established operating
level), must the unit be recalibrated or can we adjust the density
setting to obtain a 1.20 OD?
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Must
the weekly phantom test be performed for all image receptor sizes?
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Must
the interpreting physician evaluate the weekly phantom QC test?
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We
use the BACE mode in our Bennett machine to image our patients with
the standard breast. In this mode the unit automatically determines
the exposure technique factors based on the thickness of the compressed
breast. During normal clinical use, the breast compresses and the
system provides accurate thickness readings and technique factors.
However, when we use this mode (as required by the regulations) for
the weekly phantom test, we do not compress the phantom (to avoid
damaging the paddle or the phantom) leading to inaccurate thickness
readings. These inaccurate thickness readings may cause the unit to
select inappropriate exposure technique factors. Can we manually adjust
the scale to the thickness of the standard breast before we expose
the phantom using the BACE mode? Given the situation described above,
is it permissible to expose the phantom using the AEC (see Phantom
Images Exposed in Fully Automatic Mode if that is the Clinically Used
Technique), rather than the BACE mode?
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Our
facility has permanently glued the acrylic contrast disk to the phantom
at the center of the cover plate. The regulation states that the OD
be measured at the center of the phantom which would require our repositioning
the disk (which may leave permanent artifacts) or replacement of the
phantom cover. Is there another way to leave the disk in place and
still fulfill the requirement?
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What
is considered adequate weekly phantom QC monitoring for a facility
that has multiple processors and multiple units?
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We
are using an FDA cleared single-use cushion pad when performing mammograms
on some of our patients. Do we have to include the pad when performing
the phantom and dose QC tests?