The endovascular method consists of the insertion of catheters (vinyl tubes) into both groin arteries. These catheters then allow positioning of artificial tubes or stent graft(s) into the diseased blood vessel without the need for major surgery which involves opening the chest. The blood vessel problem (thoracic aortic aneurysm/lesion) will be treated using an artificial bypass tube (stent graft) that will be placed inside the diseased artery. The stent graft(s) that will be used are made of polyester graft fabric sewn to a self-expanding nickel-titanium (Nitinol) wire frame and is manufactured by Medtronic AVE, Santa Rosa California.