iaea human health series publications - SEDIM

7.4.2. Repeat image analysis7.4.2.1. Scope— Objective: To determine the number and cause of repeated digital mammograms. Analysis of these datashould help to identify ways to improve system performance and to reduce digital image repeats, associatedincreased patient dose and costs.— Frequency: At least quarterly. For the repeat rates to be meaningful, a volume of at least 250 clinicalexaminations is needed, if possible.Note: The analysis is carried out for each individual acquisition unit, rather than for the combined facility asis done in screen film mammography.7.4.2.2. Instrumentation(1) Chart showing the digital mammography repeat records (see, e.g., Fig. 28 and Chart 13(a) in Annex I) or repeatlog obtained from the acquisition workstation, provided it complies with the guidance in this publication.(2) Chart for performing the quarterly digital mammography repeat analysis (see, e.g., Fig. 29 and Chart 13(b) inAnnex I).(3) Method for counting or estimating the total number of clinical images acquired during the test period.Note: A repeated image is one that is taken for reasons of inadequate quality. It does not include additionalviews required to image selected tissue seen on the first image. It also does not include images takenfor the purposes of including tissue that could not be positioned on the image receptor due to the sizeof the breast. Images performed for QC purposes are also excluded from repeat analysis.Repeated images include those that are rejected at the acquisition workstation and those that areaborted before the exposure is complete. Causes of repeated exposures include problems withpositioning, blurred images due to patient motion, detector under- or overexposure, unacceptableartefacts, X ray equipment failures (such as generator faults), software failures (such as the acquisitionsoftware freezing or crashing), blank images, no image appearing on the acquisition workstationalthough an exposure was made and other miscellaneous problems.7.4.2.3. Methodology(1) Record each repeated exposure on the repeat record chart (Chart 13(a) in Annex I), entering the cause ofrepeated exposure, date, etc. Some acquisition systems and some PACSs allow for automated logging of thecauses of repeated exposures. This may be an acceptable means of recording the majority of repeats, providedthat the log can be easily retrieved for any specified date range and that the stated causes of repeats make upa complete list. Note that repeated exposures taken on a different date (i.e. because the radiologist remarkedthat the image was blurred) may not be logged by such software, and thus it is recommended that a chart bemaintained for such repeats, even if repeat logging software is used.Note: A ‘blank image’ occurs when an exposure is made and all the pixels in the resulting image file have thesame value such that the image displayed is all one shade. ‘No image’ occurs when an exposure ismade and no image at all appears on the screen — there is no image file and no digital record of theexposure exists.(2) At the end of each quarter, use the repeat analysis form (Chart 13(b) in Annex I) to summarize the number ofrepeats in each category.72