Only if you know
that the change is due to a change in emulsion batch. The
density control function should not be used to mask
the Policy Guidance Help System
(2) Weekly quality control tests.
FDA realizes that, due to
differences in emulsion batches, a phantom image test with
films from a new box may show variance in optical density
and density difference greater than the allowed limits (when
measured against the operating level established with films
from the previous box). In such a case, facilities are
advised to first check the whole imaging chain including the
processor performance (facilities may wish to contact their
medical physicist for help with this process). If no
problems are detected, the facility may assume the change is
due to different film emulsion batches. They may then
adjust their typical clinical technique factors to meet the
phantom optical density requirements.
Question 12: 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?
If the OD at the
center of the phantom image falls below the required minimum
of 1.20 (and/or changes by more than +/- 0.20 from the
established operating level), the facility should follow
pathway A, B, or C; below, based on the situation at the
the film is of a different type (e.g., switch from Min-R
2000 to Min-R E) from the previous week’s passing test, the
facility should establish new phantom QC operating levels.
the film emulsion batch is unchanged from the previous
week’s passing test:
Ensure that the phantom is exposed using typical clinical
conditions and that the position of the phantom and, where
appropriate, the position of the AEC detector have not
changed from that used for prior images.
Reevaluate the daily processor performance and make sure the
processor is properly optimized according to the film
the facility has been tracking mAs, check the function of
the mammography unit by comparing the mammography unit’s
current mAs output with values obtained for previous phantom
images. If the mAs has changed by more than 15%, and the
facility has been using the same kVp, the same mammography
unit density setting, and the processor is operating within
its action limits, then the medical physicist should be
called to check the entire imaging chain, including the
mammography unit. If the mAs has not changed by more than
15%, then proceed with step 4. If the facility has
not been tracking mAs, the facility should consult with its
medical physicist for what to do next.
If no problems are
found in steps 2 and 3, adjust the density control setting
to obtain an optical density of at least 1.20 at the center
of the phantom image (or obtain an optical density within
+/- 0.20 of the established operating level).
density control setting used clinically to be consistent
with the changes made in step 4.
film is of the same type but of a different emulsion batch
from the previous week’s passing test, the facility should
follow the steps as described in B 1 through 5.
If the optical
density again falls below 1.20 (and/or changes by more than
+/- 0.20 from the established operating level) the next time
the weekly phantom test is performed, the facility should
follow the appropriate pathway (based on the film emulsion
used) from the following three options:
film of a different type (e.g., switch from Min-R 2000 to
Min-R E) is used, the facility should establish new phantom
QC operating levels.
film of the same emulsion batch is used (assuming the same kVp and mammography unit density settings are used, and the
processor is operating within its action limits), the
facility should consult with its physicist and check the
entire imaging chain before performing mammograms.
film of the same type (but not of the same emulsion batch)
is used, the facility should repeat steps B 1 through 5.
also refer to the ACR manual pg 186 which states “If the
change in film OD is confirmed to be due to a change in the
film emulsion batch, and if the magnitude of the change is
within the expected batch to batch variation for that film
type, then an adjustment of the density control setting to
bring the phantom BG OD back into control is an appropriate