Reliability of tarsal bone segmentation and its contribution to MR kinematic analysis methods.

The purpose of this study was to determine the reliability of tarsal bone segmentation based on magnetic resonance (MR) imaging using commercially available software. All tarsal bones of five subjects were segmented five times each by two operators. Volumes and second moments of volume were calculated and used to determine the intra- as well as interoperator reproducibility. The results show that these morphological parameters had excellent interclass correlation coefficients (>0.997) indicating that the presented tarsal bone segmentation is a reliable procedure and that operators are in fact interchangeable. The consequences on differences in MR kinematic analysis methods of segmentation due to repetition were also determined. It became evident that one analysis method--fitting surface point clouds--was considerable less affected by repeated segmentation (cuboid: up to 0.2 degrees, other tarsal bones up to 0.1 degrees) compared to a method using principal axes (cuboid up to 6.7 degrees, other tarsal bones up to 0.8 degrees). Thus, the former method is recommended for investigations of tarsal bone kinematics by MR imaging.