Direct measurement of peri-operative change in portal blood flow and pressure is difficult in human. In the present study, computational simulation of pre-and post-operative portal blood flow and pressure was performed using computational flow dynamic (CFD) software in patients with primary liver cancers. Methods: Patients with fibrotic or non-fibrotic livers were analyzed. According to preoperative MD-CT, mesh models of portal branches were constructed. CFD software (Fluent 6.2, Fluent Inc.) was employed for flow simulation. On the Fluent 6.2, changes in flow dynamics in the remnant portal branches were simulated by virtual cutting of an interested portal branch. The simulation was also performed 14 days after the operation using DICOM data obtained at that time. Results: Relative increase in blood flow in each remnant portal branch was not uniform throughout the liver in each patient. The sudden increase in portal pressure just after the virtual cutting of interested portal branch was almost normalized by day 14 in non-fibrotic liver according to the flow simulation, while the increase in fibrotic liver did not return to the pre-operative values by day 14. These results suggest that responsive dilatation of remnant portal branches and subsequent regional regeneration could normalize the sudden increase in portal pressure after surgery in non-fibrotic livers, while the mechanism is impaired in fibrotic livers. Discussion: Computational flow dynamic simulation is useful to analyze the differences in the peri-operative portal flow dynamics and liver regeneration between non-fibrotic and fibrotic livers. Aim: To determine if ROI analysis can characterize washout in Hepatocellular Carcinoma (HCC) better than visual analysis. Methods: Surgically proven HCCs from a single institution were studied. The patients' gender, age, date of scan, date of surgery were recorded. 94 patients with pre-operative triphasic (n=67) and quadriphasic CT scans (n=27) were included. A representative section containing the lesion was selected for each case. The HU change between the precontrast and arterial (HUabsolute hypervascularity) and the HU change between the peak attenuation and late portovenous phases (HUabsolute washout) were recorded. Cases were deemed positive if the HU change was more than the standard deviation (11 HU). This was compared against visual analysis to determine if our method would increase sensitivity of CT for HCC. Results: The mean patient age was 63.7 years (range 19 to 84 years); there were 77 males and 17 females. The mean duration between surgery and the scan was 39.5 days (range 1 to 348 days). Peak enhancement was seen in the early portal venous phase in 76.6% cases. The mean HUabsolute washout was 23.8 HU (range -5 -54). ROI analysis detected 86/94 cases (91.5%). This was 12.8% more than visual assessment, which detected 74/94 cases. This was statistically significant (p=0.014). Conclusion: Visual assessment of lesion density is subjective. Quantitative measurement of lesion attenuation changes between scan phases is a simple and objective method that is more sensitive than visual assessment in determining lesion washout. Background: Abdominal ultrasonogram(USG) is a common available diagnostic tool to screen and follow up for hepatocellular carcinoma(HCC). But it has been reported that the specificity of ultrasonogram is high but the sensitivity of it is insufficient. We investigated the characteristics of HCCs that was missed in the USG but was detected in the CT. Methods: Total 122 patients who were diagnosed with HCC between December, 2003 and February, 2008 , were enrolled and analysed retrospectively. All patients were performed with a USG prior to a spiral CT. The period between USG and spiral CT was limited within 1 month. We investigated age, gender, cause(HBV, HCV, alcohol), the size of HCC(the length of long diameter), stage(modified UICC), Child-Pugh Grade, cirrhosis, tumor number, portal vein thrombosis, diffuse type of HCC, regenerative nodules(RNs), and the tumor location at segement 8 as the possible related factors.