Development of three-dimensional intraductal ultrasonography in diagnosis for bile duct carcinoma

We have performed three-dimensional intraductal ultrasonography (3D-IDUS) since 1995. 3D-IDUS is useful for evaluation of bile duct carcinoma because it has a comprehensive image display. We can produce longitudinal reconstruction images with using the functions of the 3D-IDUS systems, dual-plane reconstruction images, including radial and longitudinal reconstruction images and oblique reconstruction images. The advantage of 3D-IDUS is that the time required for the examination is reduced compared with that required for conventional IDUS. We studied the results of 3D-IDUS and pathological findings for tumor extension in 25 patients with bile duct carcinoma. Overall accuracy for depth of tumor invasion was 88%, for tumor invasion to the portal vein 92%, and for tumor invasion to the pancreas was 84%. 3D-IDUS clearly demonstrates invasion of the pancreas or portal vein. However, intraductal spreading of the tumor is difficult to diagnose precisely. Diagnostic accuracy for intraductal spreading was only 70.0%, sensitivity 60%, and specificity 80%. 3D-IDUS could not detect subsequently demonstrated histological infiltration of the fibrous layer of perimuscular loose connective tissue. Another problem of 3D-IDUS is the limitation in diagnosis of lymph node metastasis. We have to continue to study the development 3D-IDUS systems to resolve these problems.