Precision and accuracy of the dynamic endocast method for measuring volume changes in XROMM studies.

The X-ray Reconstruction of Moving Morphology (XROMM) workflow enables precise and accurate measurement of the 3D skeletal kinematics underlying animal behaviors. The dynamic endocast method built upon that workflow to measure the rate of volume change within a bounded region of interest. We measured the precision and accuracy of the dynamic endocast method, using a fish oropharyngeal cavity as a case study. Despite overestimating instantaneous absolute volume, the endocast method was found to measure rate of volume change with high accuracy. Importantly, it underestimated the rate of volume change, indicating that these measurements are conservative. We tested how variables such as alpha value and locator number impacted the accuracy of the endocast method. While the appropriate values for these variables are likely different for each application of the endocast method, we believe that our conclusions that the dynamic endocast method underestimates change in volume is generalizable.