MacKeith S, et al. - During this research, a semi-automated volume segmentation tool was comparatively assessed against standard linear method for measuring small vestibular schwannoma (VS). In addition, experts discerned if oblique tumour orientation contributed to linear measurement error. When compared to linear measurements, semi-automated volumetric measurements were found to be more repeatable for the small VS measurement. Hence, its use was recommended for clinical practice. It was also perceived that oblique orientation of VS possibly served as a contributory factor for linear measurement error.