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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.
Summary
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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. α-
feto protein not give enough information about tumor activity and
not reflect tumor behavior and prognosis in most cases.
Summary
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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.