Geometric Parameter Analysis of Ruptured and Unruptured Aneurysms in Patients with Symmetric Bilateral Intracranial Aneurysms: A Multicenter CT Angiography Study

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Fig 1.
Methodology of morphologic and geometric parameter measurements. A, CT angiography shows maximum intensity projection with a 10-mm section thickness, under ×4 magnification and a standardized window setting, of symmetric bilateral intracranial aneurysms at the internal carotid artery. B, The angle maximum aneurysm height (Hmax) and neck width measurements are schematically shown. C, Area ratio measurements. The area ratio was defined as the area of the aneurysm to the parent artery in the neck plane. The area of the aneurysm (area with blue) is π × Hp × W, and the area of the parent artery within the neck (area with red) is π × Dv × N. The red arrow indicates blood flow direction.
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Fig 2.
Graph depicting the receiver operating characteristic curves for aneurysm size, AR, SR, and area ratio in the symmetric bilateral aneurysm. The areas under the curve for aneurysm size, AR, SR, and area ratio are the following: 0.667 (95% CI, 0.571–0.762), 0.703 (95% CI, 0.612–0.794), 0.679 (95% CI, 0.585–0.773), and 0.695 (95% CI, 0.603–0.787), respectively. The receiver operating characteristic area for AR (0.703; 95% CI, 0.612–0.794; P < .001) tends to be larger than the area under the curve of the other parameters. AR had the highest area under the curve.

Table 1:

Geometric parameters of ruptured and unruptured aneurysms (x̄ ± s)

Geometric Parameters	Unruptured (n = 63)	Ruptured (n = 63)	P Value
Neck size (mm)	3.1 ± 1.3	3.2 ± 1.2	.783
Aneurysm size (mm)	4.3 ± 2.2	5.3 ± 2.0	.009
Vessel diameter (mm)	2.5 ± 0.6	2.4 ± 0.6	.687
θ_F	121.4° ± 32.7°	130.8° ± 33.6°	.104
θ_P	107.6° ± 26.6°	100.9° ± 27.1°	.159
AR	1.3 ± 0.5	1.7 ± 0.6	<.001
SR	1.7 ± 1.2	2.1 ± 0.9	.029
NPR	1.4 ± 0.7	1.4 ± 0.6	.805
Area ratio	2.0 ± 2.0	2.9 ± 1.9	.011

Note:—θ_F indicates flow angle; θ_P, parent-daughter angle; NPR, neck-to-parent artery ratio.

Table 2:

Conditional logistic regression analysis of geometric and morphologic parameters between unruptured and ruptured aneurysms

	Ruptured (n = 63)		Unruptured (n = 63)		OR (95% CI)	AOR (95% CI)
	No.	%	No.	%	OR (95% CI)	AOR (95% CI)
Aneurysm size
≥4.6 mm	44	69.8	23	36.5	3.625 (1.657–7.929)	–
AR
≥1.6	33	52.4	9	14.3	13.000 (3.086–54.771)	9.521 (2.182–41.535)
SR
≥1.7	41	65.1	27	39.0	2.556 (1.183–5.523)	0.970 (0.320–2.945)
Area ratio
≥1.5	51	80.9	30	47.6	6.250 (2.175–17.958)	4.089 (1.247–13.406)
Aneurysm wall
Irregular wall	50	79.4	15	23.8	8.000 (3.157–20.270)	10.443 (3.394–32.135)
Aneurysm shape
Spheric	31	49.2	34	53.9	0.833 (0.420–1.653)	1.078 (0.499–2.330)
Flow angles
Equivalent flow	6	9.5	11	17.5	Reference	Reference
Straight flow	43	68.3	35	55.6	2.175 (0.728–6.497)	1.749 (0.505–6.057)
Curved flow	14	22.2	17	27.0	1.457 (0.405–5.243)	2.054 (0.491–8.589)