In this present study, we found that MDCE-MRI showed different characteristics of enhancement by a time-signal intensity curve, the various parameters in assessing the degree of tumor neovascularization non-invasively. These parameters can be used for the quantitative analysis of diseases. The MET reflects the average pass time, the PEI relates to the relative blood volume, the MSI represents the microcirculatory blood flow, and the MSD reflects the blood supply of the tumor velocity [9, 10]. The mean values of MET, PEI, and MSI for benign tumors were higher than malignant tumors, and the difference was statistically significant. When the thresholds were 592.13, 120.11, and 156.97 respectively, the diagnostic specificity of these parameters were 77%, and the sensitivities were 58.80, 70.60, and 82.40% respectively. A large proportion of benign tumors is hemangiomas and the pathology of hemangiomas is mainly composed of abnormal dilatation of hepatic sinusoids. Although the MSD of benign tumors was less than malignant tumors, the difference was not statistically significant. Based on the literature, many factors can affect the enhancement type of the tumor, such as the density and permeability of the tumor vessels and extracellular diffusion space [11, 12]. We compared each parameter value among the four groups of tumors and found that the PEI and MSI values between hemangiomas, HCCs, cholangiocarcinomas, and metastatic tumors had significant differences. The MSD values between metastatic tumors and HCCs also had significant differences. Furthermore, the MET, PEI, and MSI values of hemangiomas were all higher than other tumors.
These results may have a relationship to the pathology of hemangiomas, HCCs, cholangiocarcinomas, and metastatic tumors [13,14,15,16]. The pathology of hemangiomas is composed of abnormal dilatation of hepatic sinusoids; however, HCCs develop in multistage processes with an increase in the degree of malignancy as the greater the blood supply in the hepatic artery. Cholangiocarcinomas are hypovascular tumors with increased fiber composition. According to the varied origin of cholangiocarcinomas, the blood supply of metastatic tumors is different and the rate of growth is usually rapid, thus the center of the tumor is prone to be liquefaction necrosis. Therefore, blood flow in hemangiomas is higher than other liver diseases.
Some research have suggested that parameters which are obtained from MDCE-MRI are highly related to tumor angiogenesis . Because different lesions have different hemodynamic metabolic characteristics, the enhancement curve types were varied, which reflects the blood supply of tissues and vascular permeability state. Combined with the enhancement type curve of this study, we divided the curve type into the four categories. We found that there was a significant difference between benign and malignant tumors, as well as among each four groups. Benign tumors present with type II and malignant tumors mainly present with type I. HCCs mainly present with type I, metastatic tumors and cholangiocarcinomas mainly present with type IV, and hemangiomas mainly present with type II, all of which are consistent with reports in the literature [18, 19]. This result reflects the pathologic changes of each lesion. The histologic characteristics of HCCs reflect the liver arterial blood supply, the histologic characteristics of cholangiocarcinomas reflect the hypovascular tumor containing more fibers, which results in slow contrast agent diffusion between the blood vessels and fibrous tissues. The pathologic features of hemangiomas reflect abnormal dilatation of hepatic sinusoids and the enhanced feature of metastasis depends on the blood supply of the primary tumor.
In addition, we adopted parameters that were significantly different between benign and malignant tumors and performed logistic regression analysis. We obtained the regression eq. (P = 1/[1 + e0.008 × 1 + 0.007 × 2–6.707]) and took the Youden index maximum points as the diagnostic point, which was 0.2946. When the regression equation calculated value was less than the diagnostic point, the tumor was malignant.
Due to the small sample size, there are several limitations in the article, such as, it is not possible to characterise all metastases into a single group. There is no discussion of dysplastic nodules versus HCC. And HCCs accounted for a larger proportion of the tumors in the current study. For benign tumors, hemangiomas accounted for a larger proportion. There is no mention of differences between cirrhotic and normal background livers. The main focus of the discussion is on haemangiomas, which are almost always easy to diagnose. We will increase sample size for further research.