Purpose

To explore the value of of intratumoral susceptibility signal intensities (ITSS) in quantitatively and automatically differentiating intrahepatic cholangiocarcinoma (ICC) from hepatocellular carcinoma (HCC) using enhanced T2 star-weighted angiography (ESWAN).

Introduction

The incidence of ICC is the second most common primary malignant tumor of the liver, second only to HCC [1]. ICC is more aggressive than HCC, and most surgical treatment regimens are based on lobular resection, and currently there is no effective chemotherapy method [2,3]. Therefore, the accurate differential diagnosis of ICC and HCC is helpful for clinical treatment formulation and prognosis assessment. Conventional MR imaging can effectively distinguish typical ICC from HCC according to the morphology of lesions, enhancement pattern and adjacent bile duct dilation, and so on. However, it is still difficult to distinguish atypical ICC from HCC. In the present study, we proposed that ITSS could be a promising imaging biomarker for differentiation of ICC from HCC.

Materials and Methods

From August 2015 to November 2020, 46 patients who were pathologically confirmed as ICC (n = 20) or HCC (n = 26) in our hospital. All patients underwent abdominal MR examinations with 1.5T MR scanner (Signa HDxt, GE Medical Systems, USA), including T1WI, T2WI and 3D gradient echo (GRE) ESWAN sequence. Detailed MR scanning parameters are shown in Table 1. All images on ESWAN sequence were transferred to the GE AW 4.6 workstation for post-processing in Functool software. Due to the acquisition, there are banding artifacts in the phase image as shown in Figure 1 (a). Therefore, the workflow shown in Figure 1 is first used to remove artifacts from the input phase map. The workflow is as follows: (i) Firstly, the abnormal pixels with high gray value and low gray value in the phase map are detected; (ii) Then, the artifact region is determined according to the feature of adjacent pixels of high pixel value and low pixel value; (iii) Finally, the pixel values in the artifact region are recalculated according to the gray values of the surrounding non-artifact pixels. Phase map after using batch program to remove artifacts were exported as NII format, and transmitted to AnatomySketch (AS) software, which is programmed using C++ based on Qt and VTK libraries (Dalian University of Technology). Referencing to T2WI images, regions of interest (ROIs) were delineated around the edge of the tumor on phase maps (Figure 2). ROI can be obtained without layer-by-layer annotation through the interpolation and annotation tools of AS. After that, the AS software can automatically calculate the ITSS ratio of the phase maps. ITSS ratio was defined as the ratio of ITSSs to the lesion involving area on tumor maximal axial section [5]. All statistic analyses were analyzed by SPSS 25.0 software. Normal distribution was tested by Shapiro-Wilks test. ITSS values between ICC and HCC were compared using Mann-Whitney U test. Receiver operating characteristic (ROC) analysis was performed to evaluate diagnostic performance.

Results

The ITSS value of ICC group was higher than that of HCC group (P < 0.001, shown in Table 2). The AUC of quantitative ITSS was 0.927, a sensitivity of 85.0%, a specificity of 92.3% (Figure 3).

Discussion and Conclusion

This study showed that quantitative ITSS value had good performance in differentiating ICC from HCC. Because of hypoxic microenvironment and more easily ruptured abnormal neovessels, deoxygenated hemoglobin and hemoglobin decomposition products increased [4]. In the present study, we proposed that ITSS could be a promising imaging biomarker that allow differentiating ICC from HCC.Theoretically, the higher the degree of malignancy, the more complex the internal structure, and the more magnetic sensitive substances contained in the tumor, the higher the ITSS value. At the same time, ICC has a higher degree of malignancy than HCC, whose with more complex internal structure and magnetic sensitive substances.

Acknowledgements

No