A variable magnet system for manipulating a magnetic catheter is described. In one embodiment, a cluster of electromagnets is configured to generate a desired magnetic field. In one embodiment, one or more poles of the cluster are moveable with respect to other poles in the cluster to allow shaping of the magnetic field. In one embodiment, one or more magnetic poles can be extended or retracted to shape the magnetic field. In one embodiment, the electromagnets can be positioned to generate magnetic fields that exert a desired torque and/or movement force on the catheter. In one embodiment, a magnetic field source is used to create a magnetic field of sufficient strength and orientation to move a magnetically-responsive catheter tip in a desired direction by a desired amount.
