Embodiments of an injector, syringe, syringe interface, syringe adapter, and piston/plunger assembly for an injector (of contrast medium, for example) are described. Preferably, the syringe is adapted to engage a syringe interface mechanism such that the syringe may be connected to an injector without regard to any particular orientation of the syringe to the injector or to the piston/plunger assembly. The injector piston or drive member includes a sensing pin positioned at a forward end thereof to sense contact with the syringe plunger during advancement of the piston or drive member to contact the plunger. The piston can be advanced automatically upon connection of, for example, the syringe to the injector, or piston advance can be automated to occur after operator initiation. The injector may include or be adapted to accommodate two syringes, which for example provide for simultaneous injection of fluid into separate injection sites on a patient.