iaea human health series publications - SEDIM

(13) Using the annotation tool on the workstation, measure the length of each of the known reference distances.Record the results on Chart 6 in Annex II.8.5.3.4. Interpretation of results and conclusionsTolerances:(1) The effective del width and length (x and y) dimensions should be within 5% of each other.(2) The image size (in cm) in each dimension should be within 10% of the manufacturer’s stated nominal imagesize.(3) The distances measured using the annotation tool should be within 5% of the true size. If the manufacturerspecifies that the annotation tool reports distances referred to some other plane, then either the pattern can beplaced in that plane or a magnification correction can be applied.(4) There should be less than 2% deviation from a straight line over a 100 mm length in the centre of the field (i.e.the line should not deviate from its true path by more than 2 mm over 100 mm).Note: The design of some scanning systems (e.g. a curved breast support plate) may introduce a geometricdistortion. In this case, the amount of distortion should be characterized at machine commissioning.Thereafter, the test should measure whether the distortion has changed over time. Note that distortionscan influence the accuracy of needle placement in the breast, and this factor should be kept in mind.8.5.3.5. Recommendations and corrective action(1) If the del dimensions and/or the image size do not conform to the specifications above, seek service or advicefrom a qualified service engineer.(2) If there is any significant resolution non-uniformity or pattern distortion, rotate the image on the monitor by90 o . If the resolution non-uniformity or distortion persists, there is a detector problem; otherwise, it may be asoftware or monitor problem. Seek service from a qualified service engineer to have the problem corrected.8.5.3.6. Time frame for corrective actionImmediately: Corrective action should be taken before any further patients are imaged.99