The Auxiliary Diagnosis and Imaging Characteristics of MRI Combined with CT in Patients with Cholangiocarcinoma

Background Patients with cholangiocarcinoma (CCA) have poor prognosis and high mortality. Therefore, early detection and early diagnosis are extremely important to control the development of CCA. This study aims to explore the diagnostic effect in patients with CCA and imaging characteristics of MRI combined with CT. Methods 109 patients with suspected CCA underwent CT and MRI before diagnosis. The examination results were compared with the “gold standard.” ROC curve was drawn to analyze the diagnostic efficacy of MRI combined with CT for CCA patients. Results The diagnosis rate of suspected CCA patients was 95.41%. The diagnostic coincidence rate of CT and MRI examination was 89.42% and 92.31%, respectively. The diagnostic coincidence rate of MRI combined with CT examination was 100.00%. The number of CT delayed enhancement, peripheral bile duct dilatation, and hepatic capsular depression were more than those of MRI. The number of circular enhancement cases in the CT group was less than that in the MRI group. ROC curve results showed that the sensitivity and specificity of MRI combined with CT for the diagnosis of CCA patients were higher than those of MRI or CT alone. Conclusion MRI combined with CT has high diagnostic sensitivity and specificity and can provide imaging evidence for the clinical diagnosis and treatment of CCA.


Introduction
Cholangiocarcinoma (CCA) is a primary liver cancer that occurs in the bile ducts of the liver. e prognosis of CCA patients is poor and the mortality rate is high. Most patients cannot be cured, and a small number of patients with early CCA can be clinically cured. CCA lacks typical clinical symptoms in the early stage of onset. In the advanced stage of CCA, symptoms such as upper abdominal discomfort and hepatomegaly may appear [1]. erefore, the clinical diagnosis and treatment of CAA is more difficult.
Previous studies have shown that CCA is a tumor that occurs from the confluence of the left and right hepatic ducts (hilar) to peripheral bile duct epithelial cells [2]. Histopathological examination is a commonly used diagnostic method for CCA patients and is regarded as the "gold standard." However, this method has poor reproducibility and requires the professional skills of doctors. It is easy to result in poor diagnosis compliance and tolerability in CCA patients [3,4]. erefore, simple and effective diagnostic methods are of great significance to patients with CCA.
CT is a commonly used imaging method, which has a good effect on the display of microcalcification in the lesion. MRI is more sensitive to intratumoral hemorrhage [5]. It has been shown that MRI combined with CT can give full play to the advantages of different imaging methods in the diagnosis and identification of malignant tumors [6]. At the same time, MRI combined with CTdetection can evaluate the severity of the patient's disease according to different imaging features [7]. erefore, this study aims to explore the auxiliary diagnosis in CCA patients and imaging characteristics of MRI combined with CT.

Patients.
is is a retrospective study. 109 suspected CCA patients in the First Affiliated Hospital of Fujian Medical University were selected from February 2017 and December 2020. ey are between 31 and 79 years old, with an average age of 59.39 ± 5.65 years old. e diameter of the tumor is between 23 and 135 mm, with an average diameter of 64.29 ± 6.61 mm. e clinicopathological factors of these patients are shown in Table 1. e study was approved by the Ethics Committee of the First Affiliated Hospital of Fujian Medical University. And the informed consent forms of these patients were obtained.

Inclusion and Exclusion
Criteria. Inclusion criteria include the following: (1) patients are diagnosed by pathological examination and in line with CCA diagnostic criteria [8]. Exclusion criteria include the following: (1) patients with mental disorders, cognitive dysfunction, or other malignant tumors; (2) patients receiving radiotherapy, chemotherapy, and biological immunotherapy before the examination; (3) patients with autoimmune system diseases and abnormal blood coagulation function.

Treatment Method.
All patients were diagnosed by histopathological examination (gold standard). Before the diagnosis, all patients underwent CT and MRI examinations.

CT Examination.
e Lightspeed VCT scanner is used to examine patients. Before the examination, the pathogenesis, clinical manifestations, and examination methods of CCA were explained to patients and their families to improve the cooperation of the patients. Patients were instructed to perform routine fasting examinations and routinely take 800-1000 mL of negative contrast agent before the examination. During the examination, the patient was placed in a supine position. And the relevant parameter settings were completed according to the patient's condition. Finally, the unscanned and enhanced 5 mm layer thickness image was reconstructed as a 0.625 mm image. And the coronal and sagittal image reconstruction was completed [9, 10].

MRI Examination.
After completing the CT examination, MRI examination is performed according to the patient's wishes. e instrument is a 3.0 T Inegenia superconducting magnetic resonance scanner (Philips, Netherlands) using a 32-channel volume phased array coil. It takes about 18-23 s to complete the liver scan and imaging. Relevant parameters were set according to the patient's condition. e obtained images are transferred to the processing software. e examination results are compared with the "gold standard." Finally, the diagnostic coincidence rate of different imaging examinations is analyzed. And the imaging characteristics of CT and MRI are recorded [11,12].
2.6. Statistical Analysis. SPSS24.0 software was used to analyze the data. e difference between the two groups was analyzed by the χ 2 text. e ROC curve was used to analyze the diagnostic efficacy (sensitivity and specificity) of MRI combined with CT in CCA patients. P < 0.05 indicates that the difference is statistically significant.

Comparison of the Diagnostic Coincidence Rate of MRI
and CT in Patients with CCA. Among the 109 suspected CCA patients, 104 patients were confirmed by histopathological examination. And the diagnosis rate was 95.41%. CT examination confirmed 93 cases, and the diagnosis coincidence rate was 89.42% (P < 0.05, Figure 1). 96 cases were confirmed by MRI examination. e coincidence rate of MRI diagnosis was 92.31% (P < 0.05, Figure 1). 104 cases were diagnosed by MRI combined with CTexamination, and the diagnosis coincidence rate was 100.00% (P > 0.05, Figure 1).

Comparison of Imaging Characteristics between MRI and CT in Patients with CCA.
e CT group and the MRI group had no significant difference in enhancement, "fast-in and fast-out" enhancement, smooth enhancement ring, flatness, hepatic lobe atrophy, DWI high signal, and abnormal perfusion (P > 0.05, Table 2). e number of delayed enhancement, peripheral bile duct dilation, and hepatic capsule depression in the CT group were more than those of MRI (P < 0.05, Table 2). e number of uneven enhancement cases in the circular-enhanced CT group was less than that of the MRI group (P < 0.05, Table 2).

Diagnostic Efficacy of MRI Combined with CT in Patients
with CCA. ROC curve results showed that the sensitivity and specificity of MRI combined with CT for CCA patients were higher than those of MRI and CT alone (P < 0.05, Table 3, Figure 2).

Discussion
CCA is a malignant tumor with high clinical incidence. At present, it is generally believed that the incidence of CCA is related to intrahepatic bile duct stones, long-term chronic inflammation, or related physical and chemical stimulation [13,14]. Even worse, the clinical diagnosis and treatment of CCA is difficult because of the lack of typical clinical symptoms in the early stage of CCA. erefore, most patients are already in the middle and advanced stages at the time of diagnosis. Now, histopathological examination is still the "gold standard" for the diagnosis of patients with CCA. Although pathological examination is helpful for diagnosis, diagnostic compliance and tolerance are poor [15,16]. erefore, it is very important to explore new diagnostic methods of CCA in clinical practice.
In recent years, MRI combined with CT has been used in patients with CCA. Moreover, the diagnostic accuracy of MRI combined with CT is satisfactory [17]. In this study, 104 of 109 suspected CCA patients were confirmed by histopathological examination. e diagnosis rate of histopathological examination was 95.41%. In addition, the diagnosis coincidence rate of CT and MRI examination was 89.42% and 92.31%, respectively. More importantly, the diagnosis coincidence rate of CT combined with MRI reached 100.00% in this study. ese results indicate that the diagnostic accuracy of MRI combined with CT is very high. Qi et al. [18] also reported that MRI combined with CT can achieve a    Male  Female  Abdominal pain  Jaundice  Fever  Fatigue  CT  MRI  CT + MRI  Cases  65  44  32  16  19  29  57  29  23 higher detection rate in patients with CCA. Briefly, MRI combined with CT examination is helpful to the early diagnosis of CCA patients and can guide the clinical diagnosis and treatment. It is well-known that fibrous tissue, mucin, coagulative necrosis, and malignant tumor tissue cells are the main components of the mass. And according to the area, tissue type, and distribution characteristics of the tumor, there are obvious differences between different components [19]. It has been found that the imaging manifestations of CCA mainly depend on the pathological type, the distribution of fibrous tissue, and tumor cells [20]. e tumor cells are distributed around the tumor, and the proliferating fibrous tissue is located in the center of the tumor. e contrast agent diffuses slowly in the fibrous tissue and can obtain clear images [21].
In this study, the CT group had more cases of delayed enhancement, peripheral bile duct dilation, and hepatic capsule depression than MRI. e number of uneven enhancement cases in the CT group was less than that of MRI.
e above results indicate that MRI and CT have typical imaging characteristics in patients with CCA. e diagnosis of different lesions can be confirmed through imaging features. In order to further analyze the diagnostic value of MRI and CT in patients with CCA, ROC curves were drawn in this study. e results showed that the diagnostic sensitivity and specificity of MRI combined with CT in patients with CCA were higher than those of single MRI and CT. erefore, MRI combined with CT examinations should be strengthened for patients with suspected CCA. However, the number of samples in our study is a little small. We will continue to collect data in the follow-up to better confirm our conclusions.

Conclusion
In conclusion, MRI combined with CT can achieve a high diagnostic coincidence rate in patients with CCA and has typical imaging features. Moreover, the sensitivity and specificity of the combined examination are high. erefore, MRI combined with CT can provide imaging basis for the clinical diagnosis and treatment of CCA.
Data Availability e datasets used and/or analyzed during the present study are available from the corresponding author on reasonable request.

Conflicts of Interest
e authors declare that they have no conflicts of interest.