Low-dose Gated CT Validity for the Evaluation of Ascendant Aortic Aneurysm.

We will demonstrate the validity of measurements with a low-dose, EKG-gated CT without contrast in the ascending aorta evaluation, compared with the current Angio-CT measurements.

The actual protocol used in aorta evaluation consist of two CT-scans on the same study. The first scan that detects calcifications is using parameters with low-dose current, non EKG-gated and without contrast. The second scan uses iodine-contrast, EKG-gating and higher current dose to obtain higher image quality of diagnostic value. The study will optimize the first scan parameters and compare the measures of the aorta diameters from the standard protocol. By modifying the first scan parameters, we would demonstrate that the follow-up of an aortic aneurysm can safely be made with lower radiation exposure.

Subjects already waiting for an aortic evaluation, either a first diagnostic scan or follow-up of a known aneurysm. Each subjects will have the two CT-scans on the same day.

On the same day, the subject will do : Modified low-dose, EKG-gated CT without contrast Usual high-dose, EKG-gated CT with contrast Comparing aortic diameters from the two protocols.

Inclusion Criteria: 60 years old and more 85 bpm or less Exclusion Criteria: aortic material EKG gating not possible aorta pathology (thrombus, dissection)