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Impact of adaptation time on contrast sensitivity
|Manning, D.J. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:|
Medical imaging 2010: Image perception, observer performance, and technology assessment : 17 - 18 February 2010, San Diego, California, United States
Bellingham, WA: SPIE, 2010 (Proceedings of SPIE 7627)
|Conference "Image Perception, Observer Performance, and Technology Assessment" <2010, San Diego/Calif.>|
Medical Imaging Symposium <2010, San Diego/Calif.>
| Conference Paper|
|Fraunhofer MEVIS ()|
For softcopy-reading of mammograms, a room illuminance of 10 lx is recommended in standard procedures. Room illuminance affects both the maximal monitor contrast and the global luminance adaptation of the visual system. A radiologist observer has to adapt to low luminance levels, when entering the reading room. Since the observer's sensitivity to low-contrast patterns depends on adaptation state and processes, it would be expected that the contrast sensitivity is lower at the beginning of a reading session. We investigated the effect of an initial time of dark adaptation on the contrast sensitivity. A study with eight observers was conducted in the context of mammographic softcopy-reading. Using Gabor patterns with varying spatial frequency, orientation, and contrast level as stimuli in an orientation discrimination task, the intra-observer contrast sensitivity was determined for foveal vision. Before performing the discrimination task, the observers adapted for two min utes toan average illuminance of 450 lx. Thereafter, contrast thresholds were repeatedly measured at 10 lx room illuminance over a course of 15 minutes. The results show no significant variations in contrast sensitivity during the 15 minutes period. Thus, it can be concluded that taking an initial adaptation time does not affect the perception of lowcontrast objects in mammographic images presented in the typical softcopy-reading environment. Therefore, the reading performance would not be negatively influenced when the observer started immediately with reading of mammograms. The results can be used to optimize the workflow in the radiology reading room.