Hertel-exophthalmometry-like multi-detector-row-CT-exophthalmometry: inter-disciplinary inter-observer reproducibility of measurements.

Abstract

To investigate the inter disciplinary inter observer reproducibility of Hertel-exophthalmometry-like protrusion measurements on multi detector-row-computed-tomography- (MDCT-) images of the orbit to facilitate structured evaluation of the orbit and mid-face. Respective reproducibility of base-length along the inter fronto-zygomatic line, right and left ocular protrusion, and deriving inter ocular difference was measured in this retrospective (04/2009-03/2020) single-centre observational study. MDCT-series and slice-positions were selected independently, using picture-archiving-and-communication-system- (PACS-) tools on tilt-corrected axial MDCT-images (slice-thickness 0.6-3.0 mm, window/centre 350/50 HU) in thirty-seven selected adult patients (twenty-four female, age 57 ± 13 years, average ±standard-deviation) with clinical indication for Hertel-exophthalmometry, by one radiology-attending, two ophthalmology-attendings, one critical-care-attending, and one ear-nose-throat-surgery resident, respectively. Bland-Altman plots and Wilcoxon-matched-pairs-signed-rank-tests compared inter observer results. Mean and median inter observer and intra observer (radiology-attending) deviations were within 1 mm of respective averages of base-length (98 ± 4 mm), right and left ocular protrusion (21 ± 4 mm) and inter ocular difference (2 ± 1 mm). Relative inter observer deviations were within 2.0% of average (all patients) for base-length, and 5.0% (>80% of patients) for ocular protrusion. Pairwise inter observer comparison showed no significant differences between inter ocular differences of protrusion. Respective measurements of base-length, ocular protrusion, and deriving inter ocular difference show high inter disciplinary inter observer reproducibility in tilt-corrected axial MDCT-images of the orbit or mid-face. Hertel-exophthalmometry-like protrusion measurements did not depend on the years of experience or the medical subspecialty of the observer. Measurements are objective, well reproducible and important for multiple medical disciplines and should thus be included in pertinent radiology reports.