The invention relates to a system for use in conjunction with an ultrasound device comprising: a guide cartridge configured for slidable conformation with an ultrasound device or with a component of an ultrasound device system； and a target for a detection system for locating a tip of a subdermal device, wherein the target is associated with the guide cartridge.The invention also relates to a system for use in conjunction with an ultrasound device comprising: a guide cartridge configured for slidable conformation with an ultrasound device or with a component of an ultrasound device system, the guide cartridge containing a hub； a subdermal device configured to be retained by the hub； and a target for a detection system for locating a tip of the subdermal device, wherein the target is associated with the hub or with the subdermal device.
