iaea human health series publications - SEDIM

7.1.3. Daily flat field phantom image7.1.3.1. ScopeIt is important that artefacts that could interfere with clinical interpretation be detected before image qualitydeteriorates significantly. If an artefact that looks like a dead pixel or group of dead pixels occurs, it is veryimportant to monitor whether it persists in time, and whether its position changes on successive days. Performanceof a daily flat field image allows detection and monitoring of such problems.— Objective: To ensure that clinical images produced are free of artefacts that might interfere with imageinterpretation.— Frequency: Daily.7.1.3.2. InstrumentationUniformly thick slab of PMMA. Typically this should be 45 mm thick; however, a slab of another thicknessthat has been supplied by the manufacturer for flat field correction would also be acceptable. The slab should befree of scratches and other imperfections that would cause artefacts. It should preferably cover the entire area of theimage receptor (Fig. 17). The same test object should be used each time. It is acceptable, but not required, to have acontrast disc or other fixed structure in the image.7.1.3.3. Methodology(1) Place the test object on the breast support, centred laterally and extending slightly beyond the chest wall edgeof the digital image receptor.FIG. 17. Photograph of a flat field QC test object.43