Abstract
The detection error of the lung cancer nodule has a cognitive error and a judgment error. First, it is important for readers to make the candidate nodules clearly visible in order to reduce a cognitive error. The ribs and the pulmonary vessels are misinterpreted as the candidate nodules. Hereafter for computer-aided automatic detection of pulmonary nodules, it is necessary to process the pulmonary hilar vessels which are frequently extracted as false-positives. We herein propose a new method to control the pulmonary vascular shadow near the hilum and to clarify pulmonary nodules in chest radiographs. The pulmonary vessel (or its en face view) is extracted as a continuing linear shadow and is rearranged to the neighboring brightness level using a two-dimensional histogram. Pulmonary nodules are relatively enhanced by the equalization of the brightness level of the false-positive pulmonary vessel. We evaluated the new images obtained by applying the proposed technique to 154 images with nodules in the JSRT database. A radiologist and a student evaluated the new images in a point of visibility of the nodules. In this evaluation of 117 images excluding “extremely subtle” and “obvious”, 76% of cases were clearly depicted. The brightness of the pulmonary vessel was controlled and visibility of the pulmonary nodules was well improved. Further improvement is expected by showing original radiographs and proposed images simultaneously.
