Zenith Alpha Thoracic Endovascular Graft || The Zenith Alpha" Thoracic Endovascular Graft is indicated for the endovascular treatment of patients with isolated lesions of the descending thoracic aorta (not including dissections) having vascular anatomy suitable for endovascular repair including: " Iliac/femoral anatomy that is suitable for access with the required introduction systems, " Nonaneurysmal aortic segments (fixation sites) proximal and distal to the thoracic lesion: " with a length of at least 20 mm, and " with a diameter measured outer wall to outer wall of no greater than 42 mm and no less than 15 mm.