الفهرس 
ANATOMY OF LIVEROnly 14 pages are availabe for public view
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Abstract
Focal hepatic lesions constitute a daily challenge in the clinical setting.
It is divided into benign and malignant neoplasms.
The two most common non-cystic benign focal lesions are hemangioma and focal nodular hyperplasia.
the liver is affected by primary malignant tumour and secondary ,it is the most frequently involved organ by metastases .
Liver metastases most often arise from primary tumours in colon, breast, lung, pancreas and stomach.
Hepatocellular carcinoma (HCC) is the most common primary cancer of the liver ranking the sixth in the world and the third most common cause of cancer-related death
There is widespread use of imaging modalities such as ultrasonography (US), computed tomography(CT), and magnetic resonance imaging ,scintigraphy for there diagnosis however, scintigraphy is limited by the poor spatial resolution, and the difficulty in separation of overlapping components of the arterial and portal venous blood flow of radiotracer. Positron emission tomography is limited due to the high cost. Doppler US cannot directly measure blood flow in the hepatic parenchyma itself, although it can directly measure flow in the large feeding vessels. MR imaging is used as a semiquantitative analysis to assess perfusion changes, but has difficulties in the quantification of hepatic blood flow (HBF), because MR contrast medium does not show a linear correlation to the concentration of the contrast medium.
The liver has a dual blood supply, and changes of blood supply are always caused by liver diseases, so it is important to evaluate the hemodynamic changes to discover the diseases early. CT perfusion is a technique that has been used to analyze the complex liver blood supply by taking into account the blood input from both the hepatic artery and portal vein.
CTP offers the indisputable advantages of being noninvasive, relatively inexpensive. For initial localization of the tumor, a CT scan of the abdomen is obtained without contrast medium during a breath hold at the end of expiration. After tumor localization, a tumor region is selected independently for the dynamic study in the maximal diameter of the tumor. A dynamic study of the selected area was performed in a single breath hold at the end of expiration at a static table position. CT perfusion is a technology that allows quantitative assessment of various parameters, such as tumor blood flow (BF), blood volume (BV), mean transit time (MTT), and permeability surface area product (PS).
Changes in perfusion parameters are valuable in qualitative and differential diagnosis of different hepatic focal lesions even before occurrence of morphologic change .