Nasolacrimal system aeration on computed tomographic imaging: effects of patient positioning and scan orientation

Figures & data

Figure 1 Axial image illustrating a fully opacified (white arrow) and a fully aerated (black arrow) lacrimal sac.

Figure 2 Axial image illustrating an opacified (small arrow) and a partially aerated (large arrow) nasal lacrimal duct.

Figure 3 Coronal image illustrating an opacified (small arrow) and a fully aerated (large arrow) lacrimal sac.

Figure 4 Coronal image illustrating an opacified nasolacrimal duct (arrow). Notes: Due to patient rotation, the contralateral duct cannot be viewed in this frame.

Figure 5 Coronal image illustrating a fully or partially aerated nasolacrimal duct (arrow).

Notes: The areas of density seen superiorly and inferiorly were interpreted as fluid within the duct by some reviewers.

Table 1 Overall identification of air in the nasolacrimal drainage system for all patient positions (supine/upright) and scan orientations (axial/coronal), for three reviewers

	No air	Partial air	Full air
NLS	72%	12%	16%
NLD	76%	11%	14%
NLDS	70%	18%	12%

Note: (n=1,104).

Abbreviations: NLD, nasolacrimal duct; NLDS, nasolacrimal drainage system; NLS, nasolacrimal sac.

Table 2 Comparison in the aeration patterns for two scan positions (upright and supine), independent of scan orientation

	Position	N	No air	Partial air	Full air	P-value (chi-square test)
NLS	Supine	624	74%	14%	12%	0.00007
	Upright	480	70%	9%	21%
NLD	Supine	624	79%	13%	8%	5.0e^−11
	Upright	480	71%	8%	21%

Notes: Both axial and coronal images are included.

Abbreviations: N, total number of observations; NLD, nasolacrimal duct; NLS, nasolacrimal sac.

Table 3 The effects of positioning in a subset of four individuals who underwent both supine and upright imaging

	Position	No air	Partial air	Full air	P-value (Fisher’s exact test)
NLS	Supine	63%	2%	35%	0.15
	Upright	50%	12%	38%
NLD	Supine	60%	5%	35%	0.47
	Upright	50%	2%	48%

Notes: The aeration results of supine positioning on NLS are compared to the results of upright positioning on the NLS, using a chi-square analysis. The same comparison is made between aeration of the NLD in supine and upright positions (n=48).

Abbreviations: NLD, nasolacrimal duct; NLS, nasolacrimal sac.

Table 4 Nasolacrimal system aeration patterns when images are categorized by scan position (supine vs upright), location (NLS vs NLD), and scan orientation (coronal vs axial)

			N	No air	Partial air	Full air	P-value (chi-square test)
Supine	NLS	Coronal	312	74%	13%	13%	0.62
		Axial	312	74%	15%	11%
	NLD	Coronal	312	79%	15%	6%	0.14
		Axial	312	80%	11%	9%
Upright	NLS	Coronal	240	70%	9%	21%	0.94
		Axial	240	70%	10%	20%
	NLD	Coronal	240	73%	4%	23%	0.02
		Axial	240	69%	11%	20%

Notes: The aeration results of coronal and axial scans are compared for four groups: supine NLS, upright NLS, supine NLD, and upright NLD.

Abbreviations: N, number of observations; NLD, nasolacrimal duct; NLS, nasolacrimal sac.