The PDF ultrasound images interpretation is a difficult task for radiologists. The CAT PDF technique is a one of tools for PDF detection in the Cholangiocarcinoma Surveillance. This paper proposes a novel approach for Computer-aided Detection of Periductal Fibrosis in Ultrasound Images for Cholangiocarcinoma Surveillance. This technique consist of the PDF image enhancement method, the PDF edge detection method, and the PDF region identification method