Table 1.

Main stages of CAD system

Stages	Function
Image preprocessing stage	To remove noise and defect caused in image acquisition procedure, image resizing, and enhance the image intensity
Segmentation	Discontinuity-based segmentation: Partitions an image based on an abrupt change in intensity
	Similarity-based segmentation: Partitions an image according to pre-determined similarity criteria. The similarity-based method is categorized into region-based, thresholding-based, and clustering-based methods
Feature extraction	Different features are extracted according to the characteristics of lesions from the image
	These features are used to distinguish benign or malignant lesions. The feature set is usually very large and the selection of the most effective features is very critical for the next step
1 Classification	According to the selected features, the suspicious areas are classified to benign or malignant based on different classification
2 Result	Diagnosis result
3 Performance evaluation	This step evaluates the performance of CAD system