الفهرس 
pathologyOnly 14 pages are availabe for public view
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Abstract
Liver metastasis is a common clinical problem. Triphasic CT, MRI using different types of contrast, T2WI and recently DW imaging are different imaging techniques used in the diagnosis of this problem. This study aims to discussing the role of T2 weighted imaging & Diffusion Weighted imaging in diagnosis of liver metastasis. T2WI is commonly used in diagnosis of liver metastasis. Its sensitivity is about 67% yet it is not specific. DWI using different b values has high sensitivity and specificity reaching more than 90%. The ADC has the advantage of tissue characterization through ADC map and ADC values. Lesions appear high signal in DWI and high signal in ADC are termed non-restricted diffusion because f their low cellularity as cysts and hemangioma. Lesions appear high signal in DWI and low signal in ADC are cellular tumors and described as restricted diffusion pattern as metastasis. In additions the value of ADC can help in diagnosis and characterization of liver masses. Malignant masses have low ADC values < 1.2 x 10-3 , hemangioma > 1.5 to 2 x 10-3 cysts about 3 x 10-3 mm2 /sec. The DWI and ADC proved to have more sensitivity and specificity than T2WI and almost equal sensitivity as post-contrast MR study however this point needs more research. The technique of DWI & ADC proved to be of great value in detection and characterization of hepatic focal lesions especially liver metastasis. In addition it is promising in evaluating the effect of treatment of liver tumors and further investigations in this field is highly recommended. The great advantage of DWI & ADC are not using contrast media. The DWI & ADC have some limitations (1) motion artifact arising from cardiac pulsation may mask lesions in the left lobe, (2) Metastatic liver lesions having restricted diffusion pattern may overlap with solid cellular benign masses as focal nodular hyperplasia and hepatic adenoma, (3) necrotic tumors may have unrestricted diffusion pattern simulating hemangioma and cyst and (4) in follow up there is difficulty in accurate reproducibility of ADC values. DWI and ADC should be used routinely in the protocol of liver imaging. It should be used in patients with renal impairment to avoid the complication of nephrogenic systemic