Computer-aided diagnosis scheme for detecting pulmonary nodules using wavelet transform

To aid radiologists in the detection of lung cancer, we are developing a computer-aided diagnosis (CAD) system that locates areas suspicious for nodules in digital chest radiographs. The system involves a difference-image approach and various feature-extraction techniques. To improve the sensitivity of the overall scheme, we investigated an approach based on the wavelet transform. We found that the wavelet transform is effective in detecting subtle nodules that were not detected by the difference-image technique. By combining the two schemes based on the difference-image and the wavelet transform, the sensitivity was increased from 81% to 86% while maintaining approximately the same level of specificity.