Introduction
Detective flow imaging (DFI) is a novel technology that enables the evaluation of low-speed blood flow signal that is difficult to visualize with conventional Doppler techniques1)-3). This technique allows for evaluating microvascular signals within tumors in endoscopic ultrasound (EUS) without using contrast agents. In this study, we aimed to investigate the usefulness of DFI for the diagnosis of biliary tract lesions.
Aims & Methods
A retrospective study was conducted of patients who underwent DFI with EUS between September 2019 and December 2022 at our institution. Patients with biliary tract lesions diagnosed by either endoscopy or pathology were included. Malignant biliary tract lesions were defined as those with histopathological diagnoses of non-invasive or invasive carcinoma. To evaluate the diagnostic ability of DFI for malignant biliary tract lesions, we assessed the presence of tortuous or variable caliber vessels in DFI findings. Inter-observer agreement and the diagnostic ability of DFI in identifying malignant biliary tract lesions were also assessed. Additionally, the DFI findings of intraductal papillary neoplasms (IPNB) and cholangiocarcinoma in patients who underwent surgical resection.
Results
There were 17 cases of cholangiocarcinoma, 9 cases of IPNB, 3 cases of bile duct stone, and 3 other cases. The final diagnosis of biliary tract lesion was made by surgery in 20 cases and by EUS-FNA or biopsy in 9 cases. In the first analysis, the sensitivity and specificity for the presence of tortuous or variable caliber vessels for the diagnosis of malignancy were 80% and 43% for tortuous vessels and 68% and 100% for variable caliber vessels, respectively. Interobserver agreement was k=0.63 for tortuous vessels and k=0.75 for variable caliber vessels. In the second analysis, DFI identified stalk vessels in 7 of 8 cases (87.5%) of IPNB and in only 1 of 10 cases (10%) of invasive cholangiocarcinoma. The rate of concomitant stalk vessels was significantly higher in IPNB than in invasive cholangiocarcinoma (P<0.01).
Conclusion
DFI is a simple and easy-to-use technique that allows for the evaluation of blood flow in biliary tract lesions without the use of contrast agents. It has the potential to be a useful tool for the differential diagnosis of malignant biliary tract lesions.
References
1. Yamashita Y, Yoshikawa T, Yamazaki H et al. A novel endoscopic ultrasonography imaging technique for depicting microcirculation in pancreatobiliary lesions without the need for contrast-enhancement: a prospective exploratory study. Diagnostics (Basel) 2021; 11: 2018.
2. Yamashita Y, Yoshikawa T, Kawaji Y et al. Novel endoscopic ultrasonography imaging technique for visualizing microcirculation without contrast enhancement in subepithelial lesions: prospective study. Dig Endosc 2021; 33: 955–961.
3. Miwa H, Sugimori K, Maeda S. Vessel images of gallbladder polypoid lesions on detective flow imaging endoscopic ultrasonography. Dig Endosc 2023. doi: 10.1111/den.14530 [Online ahead of print].
