Ex vivo orbital volumetry using stereology and CT imaging: A comparison with manual planimetry
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To evaluate the applicability of stereology and planimetry in orbital volume measurements using computed tomography (CT) and to compare the results between the two measurements.
Experimental study using sheep craniums for CT imaging. Water filling measurements were performed, as the validation technique. Quantification techniques were also evaluated in five human subjects. To examine the proportion of agreement among measurements, we tested intra- and inter-observer agreement.
For stereology customization, a 1/8 systematic sampling scheme was considered as optimal; this resulted in a low coefficient of error (2.59 %) and low measurement time (1.9 mins). In sheep craniums, mean volume measured by water displacement, planimetry and stereology was 17.81 ± 0.59 cm3, 17.87 ± 0.68 cm3 and 17.54 ± 0.49 cm3, respectively. Total volumes, obtained by stereology, were highly correlated with the water-filling method (r=0.893; p = 0.001) and a paired t-test showed significant difference between methods (t=3.047; p = 0.014). Planimetry results displayed a high correlation with the water-filling method (r=0.957; p ≈ 0.001) but no statistically significant difference was found (p = 0.154). Mean difference using planimetry and stereology was 0.332 ± 0.322 cm3. In human subjects, using stereology, the estimated volume ranged between 18.57 cm3 and 19.27 cm3, and the mean orbital volume was 19.05 ± 0.50 cm3 with CE=3.75 ± 0.16 %. Mean measure time was 2.1 ± 0.1 mins.
• Stereology can be applied to measure the orbital volume using computed tomography.
• Stereological measurements display high correlation with gold standard planimetry and combine low coefficient of error (2.59%) with low measurement time (1.9 min).
KeywordsOrbit Eye Skull Anatomy
Coefficient of error
Intraclass correlation coefficient
Magnetic resonance imaging
This study has received funding by the General Secretariat for Research and Technology (GSRT) and the Hellenic Foundation for Research and Innovation (HFRI).
Compliance with ethical standards
The scientific guarantor of this publication is Efstathios Detorakis.
Conflict of interest
The authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article.
Statistics and biometry
One of the authors has significant statistical expertise.
Written informed consent was obtained from all subjects (patients) in this study.
Institutional Review Board approval was obtained.
• Performed at one institution
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