Quantification of aortic distensibility in abdominal aortic aneurysm using ECG-gated multi-detector computed tomography

Rationale and objectivesTo detect distensibility changes that might be an indicator for an increased risk of rupture, cross-sectional area changes of abdominal aortic aneurysms (AAA) have been determined using ECG-gated CT.Materials and methodsDistensibility measurements of the aorta were performed in 67 patients with AAA. Time-resolved images were acquired with a four detector-row CT system using a modified CT-angiography protocol. Pulsatility-related cross-sectional area changes were calculated above and at AAA level by semiautomatic segmentation; distensibility values were obtained using additional systemic blood pressure measurements. Values were compared for small Ø< 5 cm (n=44) and large Ø> 5 cm (n = 23) aneurysms.ResultsThe aorta could be segmented successfully in all patients. Upstream AAA distensibility D was significantly higher than at AAA level for both groups: means above AAA (at AAA) Dabove = (1.3±0.8)·10−5 Pa−1 (DAAA = (0.6±0.5)·10−5 Pa−1) t-test pD<0.0001. Differences of the distensibility between smaller and larger aneurysms were not found to be significant.ConclusionDistensibility can be measured non-invasively with ECG-gated CT. The reduction of distensibility within aneurysms compared to normal proximal aorta is subtle; the lack of difference between both small and large aneurysms suggests that this reduction occurs early in the aneurysm's development. Hence, reduced distensibility might be a predictive parameter in patients with high risk of aortic disease.