Assessment of Posterior Globe Flattening: Two-Dimensional versus Three-Dimensional T-Weighted Imaging

Abstract

Purpose: To compare the frequency of posterior globe flattening between twodimensionalT2-weighted imaging (2D T2WI) and three-dimensional (3D T2WI). Materials and Methods: Sixty-nine patients (31 female; mean age, 44.4 years) whohad undergone both 5-mm axial T2WI and sagittal 3D 1-mm isovoxel T2WI of thewhole brain for evaluation of various diseases (headache [n = 30], large hemorrhage [n= 19], large tumor or leptomeningeal tumor spread [n = 15], large infarct [n = 3], andbacterial meningitis [n = 2]) were used in this study. Two radiologists independentlyreviewed both sets of images at separate sessions. Axial T2WI and multi-planarimaging of 3D T2WI were visually assessed for the presence of globe flattening. Theoptic nerve sheath diameter (ONSD) was measured at a location 4 mm posterior toeach globe on oblique coronal imaging reformatted from 3D T2WI. Results: There were significantly more globes showing posterior flattening on3D T2WI (105/138 [76.1%]) than on 2D T2WI (27/138 [19.6%], P = 0.001). Interobserveragreement was excellent for both 2D T2WI and 3D T2WI (Cohen’s kappa =0.928 and 0.962, respectively). Intra-class correlation coefficient for the ONSD wasalmost perfect (Cohen’s kappa = 0.839). The globes with posterior flattening hadsignificantly larger ONSD than those without on both 2D and 3D T2WI (P < 0.001;6.14 mm ± 0.44 vs. 5.74 mm ± 0.44 on 2D T2WI; 5.90 mm ± 0.47 vs. 5.56 mm ± 0.34on 3D T2WI). Optic nerve protrusion was significantly more frequent on reformatted1-mm 3D T2WI than on 5-mm 2D T2WI (8 out of 138 globes on 3D T2WI versus oneon 2D T2WI; P = 0.018). Conclusion: Posterior globe flattening is more frequently observed on 3D T2WI thanon 2D T2WI in patients suspected of having increased intracranial pressure. Theglobes with posterior flattening have significantly larger ONSD than those without.