Experimental system for detecting lung nodules by chest x-ray image processing

摘要

Abstract: This paper describes a system for automatic detection of lung nodules by means of digital image-processing techniques. The objective of the system is to help chest physicians to improve their accuracy of detection. For detecting lung nodules in chest x-ray images, the authors developed the directional contrast filter for nodules (DCF-N), which consists of three concentric circles. The DCF-N is effective for detecting patterns with obscure peripheries, such as lung cancer. The filter was evaluated using 192 lung cancer cases, and a detection ratio of 88.5% with false-positive foci was obtained. The authors also developed a rule-based system for eliminating these false-positive foci. The rule-base contains six rules that were heuristically developed according to a common method of diagnosis used by chest physicians. By using the rule-base, the authors succeeded in eliminating 63.3% of false-positive foci without increasing the number of false-negatives significantly (5.0%). In addition to the rule- base, a logic was developed for discriminating between lung nodules and false-positive foci by using the nine measured values on each shadow. The discrimination was tested by using 192 lung cancer cases and 74 normal control cases. As a result, figures of 92.2% and 71.6% were obtained for the sensitivity and specificity of the system, respectively. To evaluate the logic by using external data, 30 cases of lung cancer and 78 control cases were collected. As a result of the evaluation, the authors obtained figures of 71.3%, 76.7%, and 69.2% for the accuracy, sensitivity, and specificity of the system, respectively.!