Figure 1.

A transverse image of an AAA from Hartshorne et al demonstrating the inner to inner measurement used in the NAAASP.³¹ The aortic diameter is measured in the anteroposterior plane. The straight arrows indicate the position of the inner anterior and inner posterior wall. The angle arrows indicate the position of the outer anterior and outer posterior wall. The asterisk indicates an area of mural thrombus on the posterior wall. The authors have shown this to demonstrate the importance of not placing the posterior inner wall calliper on the inner border of the thrombus. AAA, abdominal aortic aneurysm; NAAASP, national abdominal aortic aneurysm screening programme.