New selective nodule enhancement filter and its application for significant improvement of nodule detection on computed tomography

Abstract

Computer-aided diagnostic (CAD) schemes have been developed to assist radiologists in the early detection of lung cancer in radiographs and computed tomography (CT) images. In order to improve the sensitivity for nodule detection, many researchers have employed a filter as a preprocessing step for enhancement of nodules. However, these filters enhance not only nodules, but also other anatomic structures such as ribs, blood vessels, and airway walls. Therefore, nodules are often detected together with a large number of false positives caused by these normal anatomic structures. In this study, we developed a selective enhancement filter for nodule which can simultaneously enhance nodules and suppress other normal anatomic structures such as blood vessels and airway walls. Therefore, as preprocessing steps, this filter would be useful for improving the sensitivity of nodule detection and for reducing the number of false positives. We applied the enhancement filter to two-dimensional (2-D) and three-dimensional (3-D) CT images and also to 3-D magnetic resonance angiography (MRA) images to show its effectiveness in the enhancement of lung nodules and intracranial aneurysms.