iaea human health series publications - SEDIM

7.2.3. Weekly quality control test object and full field artefacts7.2.3.1. ScopeIn digital mammography, it is essential to perform routine assessments of the image of a test object to confirmthat there have been no substantial changes in imaging performance from the baseline. The recommended methodprovides both subjective and quantitative measures of performance.— Objective: To monitor the consistency of imaging performance (e.g. variations in detector performance) interms of factors that affect dose and image quality. Comparison is made with baseline performance levelsusing ‘for presentation’ images as viewed by the radiologist. Quantitative performance indicators are themean pixel value (MPV), mAs employed for imaging and SDNR.— Minimum frequency: Weekly.7.2.3.2. Instrumentation(1) Rectangular or D shaped phantom of uniform 45 mm thickness (Fig. 23) should be used. The same test objectshould be used each time. For this test, it is not essential that the object cover the entire field.(2) Contrast object: This could be a 1 mm deep, 25 mm diameter depression in the PMMA slab (the depressionmust have a smooth, flat bottom); a 1 mm thick, 25 mm diameter PMMA disc; or a 0.2 mm thick square ofaluminium, 10 mm on a side.(3) Baseline image of this test object obtained in a previous physicist’s test.7.2.3.3. Methodology(1) Place the test object on the breast support, centred laterally and aligned with the chest wall edge of the digitalimage receptor.(2) As appropriate, place the contrast object about 40 mm from the chest wall, on the centre line of the imagedetector.FIG. 23. The weekly QC test object with disc.57