Investig Magn Reson Imaging.  2015 Sep;19(3):178-185. 10.13104/imri.2015.19.3.178.

Assessment of Posterior Globe Flattening: Two-Dimensional versus Three-Dimensional T2-Weighted Imaging

• Ann JH
• Kim EY

• KMID: 2175612
• DOI: http://doi.org/10.13104/imri.2015.19.3.178

Abstract

PURPOSE
To compare the frequency of posterior globe flattening between two-dimensional T2-weighted imaging (2D T2WI) and three-dimensional (3D T2WI).
MATERIALS AND METHODS
Sixty-nine patients (31 female; mean age, 44.4 years) who had undergone both 5-mm axial T2WI and sagittal 3D 1-mm isovoxel T2WI of the whole 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], and bacterial meningitis [n = 2]) were used in this study. Two radiologists independently reviewed both sets of images at separate sessions. Axial T2WI and multi-planar imaging of 3D T2WI were visually assessed for the presence of globe flattening. The optic nerve sheath diameter (ONSD) was measured at a location 4 mm posterior to each globe on oblique coronal imaging reformatted from 3D T2WI.
RESULTS
There were significantly more globes showing posterior flattening on 3D T2WI (105/138 [76.1%]) than on 2D T2WI (27/138 [19.6%], P = 0.001). Inter-observer agreement 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 was almost perfect (Cohen's kappa = 0.839). The globes with posterior flattening had significantly 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 +/- 0.34 on 3D T2WI). Optic nerve protrusion was significantly more frequent on reformatted 1-mm 3D T2WI than on 5-mm 2D T2WI (8 out of 138 globes on 3D T2WI versus one on 2D T2WI; P = 0.018).
CONCLUSION
Posterior globe flattening is more frequently observed on 3D T2WI than on 2D T2WI in patients suspected of having increased intracranial pressure. The globes with posterior flattening have significantly larger ONSD than those without.

Keyword

Posterior globe flattening; Three-dimensional T2-weighted imaging (3D T2WI); Increased intracranial pressure (IICP); Optic nerve sheath diameter (ONSD)

MeSH Terms

Brain
Female
Hemorrhage
Humans
Intracranial Pressure
Meningitis, Bacterial
Optic Nerve

Figure

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  Fig. 1 2D transverse T2-weighted images and multiplanar-reformatted 3D T2-weighted images for visual assessment.

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  Fig. 2 Posterior globe flattening. Bilateral eye globes show straightening of the normal outward convexity of the sclera at the area of attachment to the optic nerve and mild indentation of posterior globes by a dilated optic nerve sheath (arrows).

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  Fig. 3 Optic nerve protrusion is noted on both 2D and multiplanarreformatted 3D T2-weighted images (arrows), but more conspicuously visualized on 3D T2-weighted images.

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  Fig. 4 The optic nerve sheath diameter (hyperintense region, dashed arrows) is measured 4 mm posterior to the eye globe on multiplanar-reformatted 3D T2-weighted images.

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  Fig. 5 Comparison of posterior globe flattening between 2D and 3D T2-weighted imaging. A 66-year-old male with acute infarcts in the bilateral frontal lobes and left parietal lobe shows posterior globe flattening on 3D T2-weighted imaging (arrows). However, it is not visible on 2D T2-weighted imaging.

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  Fig. 6 Bland-Altman plot shows a slight bias between the two observers with mean differences ranging from -0.81 to 0.68.

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  Fig. 7 Comparison of optic nerve protrusion between 2D and 3D T2-weighted imaging. A 70-year-old female with intracerebral hemorrhage shows optic nerve protrusion on both sides on 3D T2-weighted images (arrows). However, it is not noticeable on 2D T2-weighted images.

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