Significance of an additional unenhanced scan in computed tomography angiography of patients with suspected acute aortic syndrome

Table 1 Stanford classification, age and gender distribution

	AAD			IMH
n (%)	43 (76.8)			13 (23.2)
mean age (yr)	66 ± 12			69 ± 10
	Stanford A	Stanford B	A vs B	Stanford A	Stanford B	A vs B
	55.8%	44.2%		53.8%	46.2%
mean age (yr)	66 ± 11	67 ± 13	P = 0.785	65 ± 10	75 ± 13	P = 0.146
Female	41.7%	10.5%	P = 0.039	28.6%	50%

There is no significant difference in the age distribution between Stanford A and B within the entities of acute aortic dissection (AAD) and intramural hematoma. Though, in AAD there is a significant difference in the gender distribution between Stanford A and B dissections. Females showed a significantly higher percentage of type A than type B AAD. AAD: Acute aortic dissection; IMH: Intramural hematoma.

Table 2 Radiation exposure as measured by the computed tomography dose-length product

	DLP [mGy*cm]
	Mean	Min	Max
Triphasic CT scan (unenhanced, arterial and venous)	2737.2	1583.0	4476.9
Biphasic CT scan (arterial and venous)	2134.6	766.2	3494.7
Unenhanced acquisition (percentage of a triphasic CT scan)	602.6 (22.0%)

Adding an unenhanced acquisition to a biphasic computed tomography (CT) scan does, as expected, increase radiation exposure, however to a moderate degree. On average the unenhanced acquisition contributes only about 22% to the total radiation dose of a triphasic CT scan. DLP: Dose-length product.

Table 3 Complications and secondary findings n (%)

	Total	AAD		IMH
		Stanford A	Stanford B	Stanford A	Stanford B
Subadventitial hematoma of pulmonary trunk	5 (9.1)	2 (8.3)	0	3 (42.9)	0
Pericardial effusion	20 (35.7)	11 (45.8)	4 (21.1)	5 (71.4)	0
Pleural effusion	14 (25.0)	4 (16.7)	6 (31.6)	2 (28.6)	2 (33.3)
Abdominal aortic aneurysm (AAA)	17 (32.1)	2 (8.7)	12 (66.7)	0	3 (50.0)
Bleeding/rupture	4 (7.1)	0	3 (15.8)	0	1 (16.7)
Branch vessel involvement	33 (66.0)	17 (81.0)	12 (70.6)	3 (50.0)	1 (16.7)
Ischemia	10 (18.2)	5 (20.8)	4 (22.2)	1 (14.3)	0
Kidney	7 (12.5)	4 (16.7)	3 (15.8)	0	0
Liver	2 (3.6)	1 (4.2)	1 (5.3)	0	0
Spleen	3 (5.5)	0	2 (11.1)	1 (14.3)	0
Intestine	1 (1.8)	0	1 (5.3)	0	0

Branch vessel involvement was the most frequent complication. Subadventitial hematoma involving the pulmonary trunk was present exclusively in patients with Stanford A lesions. Pericardial effusion was significantly more frequent in Stanford A lesions. AAD: Acute aortic dissection; IMH: Intramural hematoma.