CQDSA in Evaluation of Prognosis After EVAR

Intra-procedural DSA series are transferred to a research workstation to generate the color-coded images and make quantitative measurements. Region of interest (ROI) measurements are performed equivalently in the endoleak and the aorta after the image generation. There are three kinds of ROIs including a small circle area with the shortest time to peak, a circle area with peak contrast intensity and the whole endoleak area. The ROI and a reference at the same latitude within the aorta are selected to undergo measurement which reflected the endoleak hemodynamics of the endoleak to the utmost extent.

The following parameters will be acquired through the CQDSA for analysis.

• Time-versus-ROI contrast intensity graph. The graph contains one endoleak ROI flow curve and one reference aortic flow curve (Ref). The x-axis shows time from 0 second to the maximum frame time of the image. The y-axis shows the sum of pixel intensities, namely total contrast, representing the contrast concentration within the ROI.
• ROI Peak/Ref Peak. It is the ratio of intensity peak between the endoleak and the reference in the aorta.
• ROI TTP (Time to peak). Peak time of ROI in the vicinity of endoleak entry.
• ROI AUC/Ref AUC. Area under curve (AUC) is calculated through Time-versus-ROI contrast intensity graph. The parameter here is the ratio of ROI AUC in endoleak to the reference.

Inclusion criteria

• Patients who present type I or/and type III endoleak after EVAR for AAA and complete at least 3 months' follow up.

Exclusion criteria

• Patients who

• undergo surgeries which involve the segment covered by EVAR;
• present connective tissue disease, such as Marfan's Syndrome or vasculitis.
• present abdominal aortic dissection.
• present AAA rupture.
• die from non aneurysm-reltated reasons or are lost during follow up.