A system and method for quickly detaching an implant and for locating the detachment zone of a detachable implant. A sensor determines a sudden change in the local environment as the sensor passes from within a microcatheter to being exposed to the vasculature. The sensor may be a temperature sensor, ultrasonic sensor, pressure sensor or the like. If the detachable implant assembly uses a heater coil to detach the implant, the heater coil may be used as a sensor. Additionally, the implant itself may be used as a sensor if a change in electrical resistance is detectable as the implant exits the microcatheter and changes shape.