Evaluation of a television image processing system.

Abstract

An image processing device using television and a scanning contrast enhancer has been evaluated by study of error rates of 13 observers viewing a standard series of chest x-rays. A technique for creating artificial lesions which simulate parenchymal masses was developed, allowing known densities to be put in known locations in otherwise normal chest x-rays. Detection was chosen as the criterion of performance. An image processor can be considered useful if percentage error is decreased. Observers were shown a series of 54 chest x-rays on a conventional viewbox and on the television monitors of the image processor. A statistical comparison of error rates was used to evaluate the system. The results show that the unprocessed television display degraded performance considerably. The addition of contrast enhancement improved error rates but direct viewing was still superior to image processing. A detailed study of error distribution showed that, using image processing, observers made considerably poorer judgments on lesions in the lower chest areas than in the upper. In the upper areas there was a trend toward lower error rates with image processing than with direct viewing although a statistically significant difference could not be demonstrated. The possible reasons for the error rate variations are discussed.