Introduction
Multidetector CT technique
Scanner | Rotation time (s) | Collimation | Table feed (mm/s) | Slice thickness (mm) | Slice interval (mm) | Duration (s) |
---|---|---|---|---|---|---|
4 slice | 0.5 | 4 × 1 mm | 25 | 1.25 | 1 | 25-30 |
16 slice | 0.5 | 16 × 0.625 mm | 27.5 | 0.625 | 0.625 | 25-30 |
64 slice | 0.5 | 64 ×0.625 mm | 80 | 0.625 | 0.625 | <15 |
Stent-grafts
Patency
Integrity
Position of the stent-graft
Sac aneurysm changes
Endoleak
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Type I is caused by separation of the device from the arterial wall, resulting in leaks originating at the proximal and/or distal attachment sites of the graft because of a technical (e.g., suboptimal stent-graft diameter) or anatomical (e.g., a short, irregular, ulcerated or angulated landing zone without an optimal conformation of the stent-graft to the curved aortic contour) problems, or to its caudal migration. On CTA images, it often appears as a huge and circumferential leak, adjacent to the proximal or distal end of the prosthesis (Figs. 9 and 10).
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Type II endoleaks are caused by back-filling of the aneurysm sac via branch vessels, such as the lumbar arteries and inferior mesenteric artery excluded by the stent-graft. On CTA images, the type II endoleak is most pronounced at the periphery of the aneurysmal sac, with little or no contact with the prosthesis, is commonly located in a posterior or lateral position, and is associated with opacification of the lumbar arteries. If an endoleak is located in the anterior position, a retrograde flow into the sac by the inferior mesenteric artery must be suspected (Fig. 11).
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Type III endoleaks arise from a fabric tear, modular or graft disconnection, and are more likely when multiple prostheses with short overlapping areas are used. On CTA images, the leak is strictly adjacent to the prosthesis, with little or no contact with margins of the aneurysmal sac, without opacification of the lumbar arteries or inferior mesenteric artery (Fig. 12).
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Type IV involves vascular flow caused by the high porosity of the graft, most likely created by the numerous suture holes holding the graft material to the stent. They are usually only detected on conventional angiograms performed at the end of the procedure.
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Type V or endotension refers to a growth of the aneurysm sac but without demonstrable reperfusion defects (Fig. 13).