Stent delivery apparatus and method

A stent delivery system for implantation of a stent in a vessel comprising:

• an elongate flexible catheter having proximal and distal ends;
• a stent having proximal and distal ends, the stent surrounding the flexible catheter near its distal end, the stent being in a delivery configuration where the stent has a reduced radius along its entire axial length;
• a retractable sheath for retaining the stent in the delivery configuration and for deploying the stent, the sheath holding the self-expanding stent in its delivery configuration against the outwardly urging force of the self-expanding stent;
• a retraction device for retracting the retractable sheath, the retraction device comprising a piston housing and a piston contained therein, the piston actatable by pressurized fluid supplied to at least a portion of the piston housing by an inflation lumen, the retraction device further comprising a connecting member, one end of which connects to the retractable sheath, the other end of the connecting member connecting to the piston,
• whereby the retractable sheath may be retracted by supplying a fluid under pressure to the inflation lumen so as to displace the piston, the piston in turn displacing the retractable sheath so as to expose at least a portion of the stent.