Accurate determination of CT-based stone volume is imperative in order to facilitate both clinical practice and research. However, conventional and widespread methods such as maximum linear measurement and ellipsoid formulae remain limited due to irregular shapes of stones. CT-based 3D Slicer, Enterprise Imaging, and Visage Imaging are alternative methods that may provide increased precision for determining stone volume.
We compare the accuracy of each of these methods, including four visage techniques, versus gas pycnometry, the gold standard for volume determination. We analyze two groups of stones, 64 small human stones under 1.5 centimeters, group one, and 54 Bego stones over 1.5 centimeters, group two. All stones underwent gas pycnometry to determine their volume. Subsequent CT scanning was completed for all stones in air and following placements in a silicone phantom.
Independent reviewers determined stone volumes using each of the seven methods. The volume determined for each stone with each method was then compared to gas pycnometry. Data were analyzed using ANOVA with Dunnett's post-hoc test, stratified by size and medium.
Enterprise imaging and visage using the Balloon Contour tool were the two methods that consistently outperformed all other methods. In air, for stones across all sizes, both were not significantly different from gas pycnometry. This was observed again in the phantom. For stones across all sizes, enterprise imaging and visage using the balloon contour tool were similar to gas pycnometry.
In this figure, the stone volume using four different methods in a phantom for a single large Bego stone is shown. Only visage and enterprise were similar to gas pycnometry.
In conclusion, the Ellipsoid Formulae consistently overestimated stone volume, regardless of stone size or imaging environment. Among all methods, enterprise imaging and visage with the balloon contouring demonstrated the most consistent accuracy, regardless of stone size. Thank you for your time.