Risk factors for rupture of abdominal aortic aneurysm based on three-dimensional study

Aneurysmal volume and surface area were measured for segment with the transverse diameter that was 3 mm or more longer than the undilated infrarenal aorta. A, Largest crosssectional area was defined as the one at the level of the maximum transverse diameter of aneurysm in the axial plane (B) .

Spiral tortuosity of AAA. Spiral tortuosity seen in AAAs consisted of two types, counterclockwise clockwise (A, B, C) and clockwise (D, E, F) . B and E are cranial-to-caudal views of 3D images A and D, respectively. C and F show their axes, which are counterclockwise and clockwise, respectively.

The ratio transverse diameter to length of aneurysm (T/L). The original aortoiliac segment (A) is shown with two types of aneurysms, spindle (B) and spheric (C) . The maximum transverse diameter is identical, and circumferential tension is the same between the two aneurysms. Focusing on the longitudinal tension, segment a ” is more stretched than segment a ' when compared with the original segment a . This difference in longitudinal tension is easy to evaluate by comparing the ratio T/L (T'/L' < T”/L”). The spheric type has advanced more in longitudinal expansion than the spindle one, if the two aneurysms have same transverse diameter.