Intra-rater and inter-rater reliability in repeated CT volumetry of adrenal glands in ferrets

Abstract

Computed tomographic imaging has previously been used to measure volumes of a variety of organs and tissues in both animals and humans. In some of these studies, intra- and inter-rater reliability have been assessed - but never has this been done in adrenal gland volumetry in ferrets. In this study, six raters with little to no experience in evaluating CT images each measured the volume of 20 adrenal glands of ferrets through manual CT volumetry. Contrast and non-contrast studies were both included, and all measurements were repeated after at least 7 days. Intra-rater and inter-rater reliability were assessed and showed good correlation (0.723 - 0.952 and 0.724 - 0.812, respectively). Application of contrast medium resulted in higher correlation compared to non-contrast ICCs (intraclass correlation coefficients) in 4/6 raters (for inter-rater ICCs: contrast: 0.721 - 0.820, non-contrast: 0.694 - 0.775. For intra-rater ICCs: contrast: 0.666 - 0.958, non-contrast: 0.622 - 0.948), thus encouraging use of contrast medium in CT volumetry of adrenal glands in ferrets. As the true adrenal gland volumes were not measured post-mortem, it is not possible to claim that the described method of CT volumetry is an accurate way of measuring adrenal gland volume. However, it can be concluded that it is a reliable method for assessing changes in adrenal gland volume over time. The reliability may be increased if measurements were performed by experienced raters instead of those with little to no experience.