Clinical application of fly-thru in diagnosis of biliary obstructive diseases: feasibility, reproducibility, and diagnostic value.

Purpose: To evaluate the feasibility, reproducibility, and diagnostic value in biliary obstructive diseases using Fly-Thru (FT) technique.

Methods: In this single-center prospective study, patients with biliary obstruction who underwent both abdominal ultrasound and FT examinations were recruited between January 2013 and January 2023. 3D FT images (3D-FT) were reconstructed with FT volumetric data. Image quality was subjectively assessed by two radiologists independently. 3D-FT was used to determine the degree of biliary obstruction and compared with ultrasound-guided percutaneous transhepatic cholangiography (PTC). Diagnostic confidence level, diagnostic accuracy and diagnostic duration of the two radiologists using 2D-ultrasound (2D-US) alone and 2D-US combined with 3D-FT were recorded respectively and compared.

Results: 100 consecutive patients were enrolled (mean age: 59.6 ± 13.2 years; 52 men). All 3D-FT images were successfully reconstructed and most (75% and 66%) 3D-FT images were considered clear and highly useful for diagnosis with a good agreement (Kappa = 0.653). Benign lesions and malignancies presented differently in both 2D-US and 3D-FT imaging. 3D-FT was not inferior to PTC in determining the degree of biliary obstruction (p = 0.101), with the sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, positive predictive value, and positive predictive value as 90.5%, 26.7%, 1.23, 0.36, 77.6%, 50.0% respectively. Combined with 2D-US, 3D-FT significantly increased the diagnostic confidence level and diagnostic accuracy of biliary obstructive diseases (all p < 0.01), especially for radiologists with less experience.

Conclusion: Application of 3D-FT in diagnosis of biliary obstructive diseases was considered feasible and reproducible, with satisfactory diagnostic value and clinical importance.