iaea human health series publications - SEDIM

7.2.4.4. Interpretation of results and conclusionsTolerances:(1) The mAs used for the phantom exposure should be within ±10% of the baseline mAs value if the kV and filterhave not changed.(2) For CR systems, the tolerances for the EI given in Table 7 should not be exceeded.(3) There should be no significant degradation of image quality from the baseline image. Note that the imagequality assessment of the phantom should yield results that are as good as or better than those expected withhigh quality screen film mammography as tested with the same phantom.(4) There should be no blotches or regions of altered noise appearance.(5) There should be no observable lines or structural artefacts.(6) There should be no ‘bright’ or ‘dark’ pixels evident.7.2.4.5. Recommendations and corrective actionsIf results are outside the tolerances or are unacceptable, the tests should be repeated. If the results remainunacceptable, it may be appropriate to contact the responsible medical physicist for further advice on implementingthe recommendations listed below:(1) If the image quality deteriorates over time, it will be necessary to carry out other investigations to determinethe source of the change 6 . A simple review of whether appropriate settings (e.g. kV, AEC, display, processingalgorithms) have been used may reveal the source of the problem. Verify whether there has been a softwareupgrade of the system that has changed the AEC settings. Otherwise, a more serious underlying problem mayrequire the assistance of the medical physicist.(2) If any artefacts are visible that might mimic or obscure anatomic information, or if any patterns are seen, arecalibration or flat fielding of the digital detector is needed. After this has been done, repeat the artefactphantom test. If artefacts persist, contact the authorized service representative.7.2.4.6. Time frame for corrective actionImmediately: If this test fails, do not image patients until corrective action has been taken.6Due to the subjectivity associated with the observer, it is recommended that the test always be performed by the same person,using the same criteria and viewing conditions.63