Embolic device delivery system with retractable partially coiled-fiber release

A medical device for placing an embolic device, such as an embolic coil, at a predetermined site within a vessel of the body including a delivery catheter and a flexible pusher member slidably disposed within the lumen of the catheter. An embolic device having a headpiece coupled to the proximal end is releasably disposed within the distal end of the pusher member and retained in place by a retractable fiber, having a coiled distal portion. When the embolic device is advanced to the predetermined site within the vessel, the detachment fiber is retracted from around the headpiece of the embolic device to thereby release the embolic device.