Abstract
ObjectiveTo apply a fully automated method to quantify the 3D structure of the bony nasolacrimal canal (NLC) from CT scans whereby the size and main morphometric characteristics of the canal can be determined.DesignCross-sectional study.Subjects36 eyes of 18 healthy individuals.MethodsUsing software designed to detect the boundaries of the NLC on CT images, 36 NLC reconstructions were prepared. These reconstructions were then used to calculate NLC volume. The NLC axis in each case was determined according to a polygonal model and to 2nd, 3rd and 4th degree polynomials. From these models, NLC sectional areas and length were determined. For each variable, descriptive statistics and normality tests (Kolmogorov-Smirnov and Shapiro-Wilk) were established.Main Outcome MeasuresTime for segmentation, NLC volume, axis, sectional areas and length.ResultsMean processing time was around 30 seconds for segmenting each canal. All the variables generated were normally distributed. Measurements obtained using the four models polygonal, 2nd, 3rd and 4th degree polynomial, respectively, were: mean canal length 14.74, 14.3, 14.80, and 15.03 mm; mean sectional area 15.15, 11.77, 11.43, and 11.56 mm2; minimum sectional area 8.69, 7.62, 7.40, and 7.19 mm2; and mean depth of minimum sectional area (craniocaudal) 7.85, 7.71, 8.19, and 8.08 mm.ConclusionThe method proposed automatically reconstructs the NLC on CT scans. Using these reconstructions, morphometric measurements can be calculated from NLC axis estimates based on polygonal and 2nd, 3rd and 4th polynomial models.
Highlights
The nasolacrimal drainage system, or tear duct, is mostly lodged in the nasolacrimal canal (NLC)
Morphometric measurements can be calculated from NLC axis estimates based on polygonal and 2nd, 3rd and 4th polynomial models
The bony NLC is defined, laterally, by the lacrimal groove of the medial side of the maxilla and by the lacrimal hook of the lacrimal bone, which scrolls over the outer edge of the canal's upper orifice; and medially, by the lacrimal bone superiorly and by the lacrimal process of the inferior nasal concha inferiorly
Summary
Using software designed to detect the boundaries of the NLC on CT images, 36 NLC reconstructions were prepared. These reconstructions were used to calculate NLC volume. The NLC axis in each case was determined according to a polygonal model and to 2nd, 3rd and 4th degree polynomials. From these models, NLC sectional areas and length were determined. Descriptive statistics and normality tests (Kolmogorov-Smirnov and Shapiro-Wilk) were established
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