Fig. 3.

a Aortic diameter in AAA with left-lateral elongation: comparison of the measurement obtained in upper abdominal cross section (right; see body marker) of 62.2 mm (D3) with the measurement of 51.8 mm (D1) when the diameter is turned on the vessel axis at the same point (left). The orthogonal diameter measurement (left) corresponds to the real diameter. The anteroposterior (AP) measurement remains constant (50.5 and 51 mm in D2 and D4, respectively). b Appropriate diameter measurement in AAA with an elongated vessel course. Measuring in abdominal cross section results in a false-high diameter due to the elliptical representation obtained in oblique section of the aneurysmal sack (D1). This measurement often also has low reproducibility, resulting in fluctuations in measured values. In order to obtain appropriate as well as reproducible measurements, the transducer should be turned in the area of maximum diameter in such a way that the real aneurysm transverse diameter (D2) perpendicular to the vessel axis is visualized (often a round structure) (modified from [20]). c A comparison of maximum AAA diameter measurement (ventrolateral elongation) of 62.6 mm (D1) in abdominal cross section in the AP plane (right) with measurement in the orthogonal plane (perpendicular to the vessel axis in longitudinal section; left). The real aortic diameter here is only a maximum of 45.5 mm (D4); at the measurement point in the AP transverse plane, it is only 39.7 mm (D3). The measurement of 62.1 mm in cross section (right) is also marked with measuring marks (D2) in the longitudinal section (left). Diameter measurement in the AP plane in the right-hand section of the image corresponds to the AP measurement on CT in an axial plane (without reconstruction). BAA abdominal aortic aneurysm, A.I iliac artery