الفهرس 
Anatomy of the LiverOnly 14 pages are availabe for public view
 |  | from | 117 |  |  |
| | | from | 117 | | |
Abstract
On a worldwide basis, primary live cell carcinoma is one of the commonest malignant neoplasms.
Most hepatocellular carcinoma (HCC) arises in patients with chronic liver disease, usually cirrhosis that especially due to HBV & HCV infection. The fibrotic and nodular parenchymal changes seen with cirrhosis make radiological evaluation of the cirrhotic liver difficult because there can be overlap in the spectrum of imaging findings of benign changes related to cirrhosis and HCC.
Recent developments in imaging techniques, particularloy CT scan and MR imaging, enable the radiologist to evaluate accurately a wide variety of focal and diffuse hepatic pathologies.
In the initial evaluation of a patients with HCC, CT is the most accurate modality for detecting extrahepatic abdominal, retroperitoneal, or chest metastases.
Tri-phasic helical CT using a large-dose bolus injection of contrast material is one of the primary methods of diagnosing hepatocellular carcinoma. Arterial phase images are better than the portal venous and delayed phase images in the detection of most hepatocellular carcinoma. Some hypovascular carcinoma are only visualized on the portal venous. The portal phase image sare also useful in differnetiaiton of a vascular structure from enhancing nodule or in the evaluation of portal vein tumor thrombosis. Several articles delayed phase CT as more usedul for the diagnosis of hypovascular tumours than arteirl and Portao venous phase.
The use of MRI is increasing for the assessment of focal liver lesions, especially hepatocellular carcinoma. However, evaluation of the liver in patints with chronic liver disease is still a major diagnostic problem. Patients with chronic hepatitis or cirrhosis of the liver have an increased risk of developing hepatocelullar carcinoma, so early detection is mandatory for optimal treatment. This need for better detection of hepatocllular carcinoma has resulted in the use of contrast agents for MRI of the liver.
HCCs are highly vascular and derive neovasculature through the process of angiogenesis. Tumor angiogenesis is a complex process mediated by several angiogenic and antiangiogenic factors and is critical for tumor growth and metastasis.
Microvessel density has been established as a prognostic indicator for many cancers, and the most direct strategy to monitor anti-angiogenic therapy would therefore be periodic biopsy. This approach is invasive, however, and likely unacceptable to patients. Moreover, estimates of microvessel density may not reflect the overall tumor biology if a single-site biopsy is used, due to the heterogeneity of perfusion within the tumor.
Although CT and MR imaging techniques have important role in early detection of disease but they no reflect the behavior and the biology of the disease. As well as serum markers e.g. a-feto protein not give enough information about tumor activity and not reflect tumor behavior and prognosis in most cases.
Noninvasive imaging, on the other hand, can be repeated in patients with larger volume coverage than biopsies. Imaging studies allow assessment of physiological parameters-such as blood volume, blood flow, permeability, and mean transit times-that reflect tumor biology.
Perfusion CT involves dynamic scanning after administration of iodinated contrast material followed by mathematic modeling to study contrast material kinetics in the tissue. Estimates of tumor perfusion parameters such as blood flow, blood volume, mean transit time, and permeability-surface area product can be derived by applying kinetic models to the CT perfusion data.
Newer generations of oncologic treatment regimens target neo-angiogenesis, delivering less systemic toxicity than did conventional cytotoxic agents. Anti-angiogenic drugs are targeted specifically to the growth factors that stimulate neo-angiogenesis.
Therefore, quantifying tumor angiogenesis is important for risk stratification, evaluation of disease progression, and monitoring response to therapy.