| Liver is one of organs into which malignant tumors, especially gastrointestinal malignancies, transfer much more easily. Many patients with primary malignancies lose the chance to receive treatment due to the widespread metastases in liver. With regard to current technical level, some liver metastasis carcinomas can't be found before excision of primary lesions, which will grow continuously after operation. And distinct liver metastases are discovered in many patients only in several months after operation. Cote reported that more than 30% patients with intestinal tract tumors had micrometastases in liver before operation, this ratio can reached up to 55-60% in autopsy of patients with malignant tumors. In rectal and colon carcinomas patients with metastases in liver, survival rate of 1 and 2 years was only 19.7% and 9.4%, but in those without metastases, they were 69.7% and 57.8%. Nowadays intraoperative ultrasonograph, enhancement scanning of multi-slice spiral CT and MRI are regarded as imageologic examination means with highest sensitivity for hepatic metastasis. For metastasis with a diameter above 1cm, their detection rate could be 95% or more. Although the detection rate of the metastases smaller than 1cm can reach 50% or so by MRI and CT, But the qualitative diagnostic rate of lesions is only 20% or less. So it becomes one of the important topics for imageologic doctors to find out good methods for detecting micrometastastic tumors. Robson presumed that hemodynamics of liver metastatic carcinoma had changed evidently even in hiding phase. The nutrition of tumors with diameter less than 1mm came from its surrounding circulation through direct diffusion. But as the diameter of tumor reached 1-3mm, new capillary network was formed around it by artery, portal vein and mixed blood capillary. As a result, hepatic arterial flow increased gradually, mean transit time of blood flow was prolonged, and portal venous flow...
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