Variation in the estimation of gallbladder volume using the sum-of-cylinders method

Ultrasound Image Based Human Gallbladder 3D Modelling along with Volume and Stress Level Assessment

Purpose

Three-dimensional (3D) gallbladder (GB) geometrical models are essential to GB motor function evaluation and GB wall biomechanical property identification by employing finite element analysis (FEA) in GB disease diagnosis with ultrasound systems. Methods for establishing such 3D geometrical models based on static two-dimensional (2D) ultrasound images scanned along the long-axis/sagittal and short-axis/transverse cross-sections in routine GB disease diagnosis at the beginning of emptying phase have not been documented in the literature so far.

Methods

Based on two custom MATLAB codes composed, two images were segmented manually to secure two sets of the scattered points for the long- and short-axis GB cross-section edges; and the points were best fitted with a piecewise cubic spline function, and the short-axis cross-section edges were lofted along the long-axis to yield a 3D geometrical model, then GB volume of the model was figured out. The model was read into SolidWorks for real surface generation and involved in ABAQUS for FEA.

Results

3D geometrical models of seven typical GB samples were established. Their GB volumes are with 15.5% and − 4.4% mean errors in comparison with those estimated with the ellipsoid model and sum-of-cylinders method but can be correlated to the latter very well. The maximum first principal in-plane stress in the 3D models is higher than in the ellipsoid model by a factor of 1.76.

Conclusions

A numerical method was put forward here to create 3D GB geometrical models and can be applied to GB disease diagnosis and GB shape analysis with principal component method potentially in the future.

Biliary motor function in gallstone patients evaluated by fatty-meal MR cholangiography

PURPOSE

To investigate the possibility of evaluating biliary motor function with magnetic resonance cholangiography (MRC).

MATERIALS AND METHODS

Twenty patients with gallstones and 30 control subjects were studied using fatty-meal MRC. After baseline MRC, they were encouraged to drink 250 mL of milk and underwent postprandial MRC every 10 minutes for 60 minutes. Postprandial changes in gallbladder volume and the diameter of the common duct were assessed as indicators of gallbladder contractility and biliary obstruction, respectively. Postprandial dilatation at 60 minutes was considered indicative of persistent biliary obstruction.

RESULTS

Gallbladder ejection fraction was calculated at 66.0% +/- 12.2% (range, 40.3%-88.6%) in the controls. Gallbladder volume expressed as a percentage of the baseline value was significantly larger at 20-60 minutes in the gallstone patients than in the controls. Gallbladder ejection fraction varied widely (mean, 46.4% +/- 24.4%; range, 2.8%-81.5%) and was significantly reduced in comparison with that of the controls (P < 0.01). In two gallstone patients with co-existing ductal stones, transient postprandial dilatation associated with ampullary impaction was observed. Persistent biliary obstruction was not indicated in any subjects.

CONCLUSION

The results of this study suggest the feasibility of fatty-meal MRC, as well as its potential for evaluating biliary motor function.