Disclosed are vascular access devices, implantable dialysis grafts, and systems including them useful for improved access to implanted medical devices. Also disclosed are implantable hemodialysis vascular access graft devices that facilitate easy, accurate and reproducible cannulation or needle entry into the implanted device by magnetically-locating a portion of the graft that includes one or more paramagnetic materials operably defining the physical boundaries of the target cannulation site/entry port.