الفهرس 
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Abstract
Liver diseases are considered serious ones because of the liver vital importance for human beings. Liver tumors are among the most frequent cancerous diseases,
which are responsible for high mortality rate worldwide {I]. Among the predominant cancer types, liver cancer is ranking at the fourth place. Medical imaging today is a valuable tool for diagnosis and treatment planning as it enables the inspection of the
whole body in a non-invasive way and allows views of anatomy. Medical decisions are rarely taken without the use of imaging modalities such as Computed Tomography (CT), which are more comfortable and safe for the patient .lmage
segmentation is the process of partitioning the image into meaningful regions with different properties such as the image intensity. The result of image segmentation is a
set of segments that cover the entire image, or a set of contours extracted from the image [2]. There are many applications of image segmentation one of these applications is medical image segmentation which could be used for different medical images. With the increasing of size and number of medical images, the use of
computers in facilitating their processing and analysis has become necessary and of great help in diagnosis and decision making in management , which is called
computer aided diagnosis (CAD )[2 J .
1.1. Computer Aided Systems
A Computer-Aided System (CAD) is a set of automatic or semiautomatic tools
developed to assist radiologists in the detection and/or evaluation of liver cancer. In
liver diagnosis, radiologists mainly use their eyes to discern cancer when they screen the Cf images. However, in many cases, cancer is not easily detected by eyes because
of the bad imaging conditions. Since screening abdominal CT scans is currently the main test for early detection of liver cancer, a huge number of.Cf images need to be
examined by a limited number of radiologists. This results in misdiagnoses due to
human errors by visual fatigue. The distinction between malignant and benign tumors sometimes is not easy because the characteristics of areas of abnormality are significant and complex. Computer Aided Diagnosis (CAD) systems can-provide such
help and they are important and necessary for liver cancer controL