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Emile Sharifi, Thao Phuong Le, Lee Mitsumori, A.J. Amadi; Three-dimensional Volumetrics of Orbital and Pre-orbital Volume. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4078.
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To evaluate and compare the reliability in measuring orbital and pre-orbital volume from axial, coronal, and sagittal CT scans.
Twelve maxillofacial CT scans were used in patients who sustained unilateral orbital blowout fractures. All measurements were done in the non-traumatized orbit. Using a post-image processing program (ADW workstation, General Electric, Fairfield, CT), volumes were measured by the manual tracing method on the axial, coronal, and sagittal scans. Orbital volume was defined as all content posterior to the orbital rim and up to, but not including the optic canal. Pre-orbital volume was defined as all tissues that lied directly anterior to, and contained within an imaginary line that perpendicularly projects from the orbital rim. The measurements were duplicated by a second investigator in five CT scans to assess interuser reliability and to test for statistically significant differences between the two measurers.
The measured orbital volume was greatest on sagittal scans 28.86 cm3 +/- 2.38, while axial scans yielded an average value of 24.45 +/- 2.09, and the coronal scans yielded an average value of 18.35 +/- 1.45. In contrast, the pre-orbital volumes were greatest in the coronal scans, 18.81 +/- 2.83, compared to 12.28 +/- 2.11 in the axial plane and 7.10 +/- 1.76 in the sagittal plane. The Pearson correlation for interuser reliability in the orbital measurements was 0.88, 0.85, and 0.86 for the axial, coronal, and sagittal planes, respectively. For the pre-orbital measurements, the Pearson correlation for interuser reliability was 0.52, 0.96, and 0.77 for the axial, coronal, and sagittal planes, respectively. None of the differences in measured values were statistically significant.
Sagittal CT scans overestimate orbital volume compared to axial and coronal scans, but sagittal scans appear to underestimate pre-orbital volume. The interuser reliability of orbital measurements were generally good with Pearson correlation being above 0.85. The pre-orbital interuser reliability measurements, with the exception of the coronal scans, were less reliable.
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