The Effect of Masking on the Evaluation of Clinical Radiographs
Abstract: The evaluation of clinical radiographs with the European Image Criteria method has in previous work proven to be an easy and straightforward method. The main drawback with this method is the large inter-observer variation. It has been proposed that the reason for this is that the observers get “distracted” by the surrounding structures in the image and that a sort of “first impression” of the image affects the following evaluation. Masking the images, and thereby removing non-critical structures, can remove the “distractions” leading to a more consistent scoring as a result. The main aim of this work was to investigate the impact of masking on the evaluation of lumbar spine and chest images based on the European Image Criteria. The evaluated image material consisted of 25 lumbar spine and 25 chest images produced with different levels of image quality. The images were evaluated by 7 radiologists using the European Image Criteria method. Each radiologist evaluated the 50 images both with and without the masking and the results were compared to each other. The variance of the Image Criteria Score (ICS) with the masking does not differ significantly from the variance without the masking when all 7 observers are included. When the results of the observers who were experts in the two different regions (spine and chest regions) are grouped together, a decrease in variance is observed when masking the images. This decrease in variance would be highly useful since a more precise scoring could be achieved with a stronger image quality separating power as a result. This decrease is not statistically significant. The observers gave a lower ICS to the masked images compared to their unmasked counterparts. One of the lumbar spine criterions needs a revision since it was nearly always fulfilled, independent of the image quality. Statistical issues hamper the variance result of masking and further studies must be carried out to validate the promising result of a decreased ICS variance between experts.
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