iaea human health series publications - SEDIM

7.2.2. Viewbox cleanliness7.2.2.1. ScopeViewboxes are a vital link in the process of interpreting a mammogram, yet they receive little attention, evenafter extensive effort has been invested in producing high quality mammograms. Particular attention should be paidto the uniformity of the luminance and the luminance level of the viewbox. Viewboxes used to review prior filmmammograms should have luminance levels of at least 3000 cd/m 2 . If hard copy laser printed films are viewed onthe same viewbox, a lower luminance may be desirable, in which case a variable brightness control would be useful.It is essential to mask the area around the mammograms to exclude extraneous light, which reduces image contrastand limits the maximum densities that can be seen without ‘bright lighting’ each film.Fluorescent tubes decrease in brightness over time, although not rapidly (i.e. about 10% in 2000 hours). It isadvisable to replace fluorescent tubes every 18–24 months. All tubes should be replaced at the same time. Inaddition, all replacement tubes should be of the same type and colour. If it is necessary to replace any fluorescenttubes because of decreased light output or for any other reason (e.g. flickering), all tubes should be replaced at thesame time to ensure uniformity of colour and luminance.— Objective: To ensure that viewboxes are clean and uniform, and that masking is available.— Minimum frequency: Weekly.7.2.2.2. Instrumentation(1) Window cleaner.(2) Soft towels.7.2.2.3. Methodology(1) Clean viewbox surfaces using window cleaner and soft paper towels.(2) Ensure that all marks have been removed.(3) Visually inspect the viewboxes for uniformity of luminance.(4) Ensure that all viewbox masking equipment is functioning properly and easily.(5) Record performance of this task on the daily and weekly checklist (Chart 1 in Annex I).7.2.2.4. Performance criteria and corrective action(1) Viewboxes should be free of dirt and marks from grease pencils or markers, etc. Any marks that are not easilyremoved with window cleaner should be removed with a safe and appropriate cleaner.(2) Viewboxes should appear uniformly bright, with the same hue. If viewboxes appear non-uniform, all thefluorescent lamps should be replaced as soon as possible. At the same time as the lamps are replaced, theinterior of the viewbox and the rear side of the viewing panel should be cleaned.(3) Masking materials should be available and easy to use. If masking materials are missing, they should bereplaced. If viewbox masks are difficult to use, appropriate service or modifications should be requested.(4) Viewboxes should be located so that they do not produce glare on soft copy reading monitors.7.2.2.5. Time frame for corrective actionImmediately: Corrective action should be taken before any further clinical films are interpreted or reviewedfor comparison with current digital images.56