iaea human health series publications - SEDIM

FIG. 38. Measurement of illumination at the radiologist’s viewing position. The illuminance meter should be facing the viewbox at adistance of approximately 50 cm.(8) Confirm that the viewbox is free of obvious dirt and marks.(9) Repeat the tests for all viewboxes used for interpreting printed mammograms and for the viewboxes used bythe radiographer to check the printed mammograms during the examination.(b)Luminance and homogeneity of the viewboxes(1) For each viewbox that is used for mammographic interpretation, turn on the lights in the viewbox at least20 minutes before taking the following measurements.(2) Assess the need to replace defective fluorescent tubes, noting any lack of cleanliness, the colour of the tubesand the viewbox panels, vibrations, etc. 31(3) Record the information on the data collection sheet.(4) Select five measurement points; one point should be centrally located, and the other four should be locatedtoward the corners of the viewbox and at least 50 mm away from the edges.(5) Place the luminance meter in contact with the surface of the viewbox at each selected point.31It is recommended that an inventory of the viewboxes in the facility be maintained, noting their location and age, andproviding a history of the replacement of the fluorescent lamps.129