Three-dimensional virtual cholangioscopy: a reliable tool for the diagnosis of common bile duct stones

Abstract

Objective: Our goal was to evaluate the clinical reliability of a new software system employing 3-dimensional (3D) virtual anatomic reconstruction and intraluminal virtual exploration for detection of choledocholithiasis and preoperative visualization of the biliary anatomy.

Summary background data: Virtual reality systems have been proposed for gastroscopy, bronchoscopy, and colonoscopy, as well as for the 3D reconstruction of liver anatomy and hepatic lesions. The impact of these systems in preoperative diagnostics has not been established due to the lack of large clinical series evaluating their reliability.

Methods: From November 2000 to July 2002, all patients presenting to our Institute with suspected choledocholithiasis were prospectively included in the study. All patients underwent conventional magnetic resonance cholangiopancreatography (MRCP) and either intraoperative cholangiogram (IOC) or endoscopic retrograde cholangiopancreatography (ERCP). The digital data from MRCP were incorporated into an original virtual reality software system to generate a 3D reconstruction. All 3D reconstructions were evaluated by a surgeon and a computer software engineer who were blind to the results of the IOC or ERCP. Sensitivity and specificity were then calculated based on the results of either the IOC or ERCP.

Results: Sixty-five patients were enrolled in the study. The average time required to reconstruct the images into navigable virtual reality was 7.5 minutes (range, 4-13.5). The 3D virtual cholangioscopy had sensitivity and specificity rates of 71% and 91%, respectively, compared with 61% and 86% of the standard MRCP.

Conclusion: : The 3D virtual cholangioscopy provides detailed preoperative reconstruction of biliary anatomy and reliable identification of choledocholithiasis with acceptable sensitivity and specificity in a clinical setting. Newer software developments may further enhance its accuracy, so that virtual cholangioscopy might challenge or replace more invasive diagnostic measures in the near future.

FIGURE 1. The anisotropic diffusion (right) reduces noise and increases contrast.

FIGURE 2. The software allows for automatic thresholding among 4 values corresponding to 4 different image resolution; the smaller the threshold, the more the details that are reconstructed. A smaller threshold is useful to identify smaller structure, but can render the figure more difficult to analyze. A larger threshold permits an easier visualization of the biliary tract, but the fine details necessary to detect stones can be lost.

FIGURE 3. Detection of 2 stones in the CBD. The stone appears as a polyp.

FIGURE 4. Normal (left) and pathological sphincter (right). Since MRI is less accurate for the analysis of the distal tract of CBD, the 3D reconstruction can make stone detection easier by enhancing the differences in shape of the distal tract of CBD.

FIGURE 5. The color can futher enhance detection of stones.

FIGURE 6. The combination and superimposition of conventional MRI onto the 3D reconstructions with transparency views also can facilitate visualization during stone detection and virtual navigation.