| Objective: To comparatively evaluate whether multi-detector row computed tomography (CT) can depict liver hemodynamic changes caused by hepatic micrometastases in rats and to correlate results with extent of tumor angiogenesis in pathologic specimens. Methods: 40 male SD rats were used in this study. Three groups of rats were divided: a experimental group (n=30), a experimental control group (n=10), a empty control group (n=10). The empty control group randomizes 10 rats from experimental group, which were scanned by CT perfusion technique before injected tumor cells. The experimental rats were injected 2×10~7 Walker-256 cells into the spleen. The rats of experimental control group were injected with saline solution. The 28 experimental rats and 10 control rats which had injected tumor cells or saline solution for 9 days were scanned and choosed section of perfusion. Subquently, the rats were scanned by CT perfusion. We obtained targeted helical CT( 5-㎜collimation, 80Kvp, 180mA) through liver. A series of CT images were obtained during 30 second. Immediately, after perfusion imaging, helical CT scans were obtained thorough liver. These images were analysed with Dynamic evaluation software at workstation. One radiologist drew regions of interest (ROI) and obtained automatically time-attenuation curves (TDC) of ROI from software. All data of TDC were interfaced a software pachage (excel 2003) of the personal computer. The livers of 22 experimental rats were sliced and stained with hematoxylin-eosin. The remaining rats were fed. The slices (4~5μm thickness) of the livers at least one represent block of formalin-fixed paraffin-embedded tissue. All samples were immunostained by using the streptomycin avidinbiotin complex technique with monoclonal antibodies against VEGF and micro vessel density which is mainly expressed on small-vesssl endothelial cells. Two experienced liver pathologists with over 20 years of experience in liver pathology recorded the histologic dignosis of each slide. VEGF and microvessel density was counted in each of three hot-spot areas on slides. Microvessel desity were determined by adding the number of vessels in each of three hot spots. The VEGF staining was graded in terms of its extent. Extent was divided into four degrees according to the percentage of tumor cells. Tumor cells were scored as (-),<5%; (+),5%~25%; (++),26%~50%; (+++),>50%. Hepatic perfusion was calculated using the gradient method. The mathematical equation: p=G/E×6000.Where p, G and E represent perfusion (units: ml.min-1.100ml-1), peak gradient of tissue and peak aortic density respectively. The liver receives its blood supply from both the aorta (through the hepatic artery) and the portal vein, and therefore has two perfusions constants.Hepatic arterial perfusion was calculated by dividing the peak gradient of the liver time attenuation curve prior to the time of peak renal cortex attenuation by the peak aortic CT number increase. Renal cortex perfusion was calculated by dividing the peak gradient of the renal cortex TDC by the peak aortic CT number increase. Portal perfusion was derived by scaling the renal cortex TDC by the ratio of hepatic arterial/(renal cortex) perfusion. This scaled curve was substracted from the liver TDC to give a portal curve. Hepatic perfusion index(HPI) expresses the proportion of hepatic perfusion that is arterial. These values which included HAP, PVP, HPI and total hepatic blood flow were compared for two control groups and experimental group. Results: Liver micrometastases of 19 rats were found from 22rats. Firstly, the values of the adjacent scan of same rat were compared by paired t-test for dependent samples. The perfusion parameters (HAP, PVP, HPI and total perfusion) were not altered significantly in different scan of the same rat. Secondly, the three groups were compared by analysis of variance (ANOVA) and Student-Newman-Keuls-q test. (1) The HAP and HPI were higher in the rats with metastases than the empty group and control group. (2) The PVP was lower in the rats with metastases th...
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