Various embodiments of syringe plunger driver or ram retraction protocols for a power injector are disclosed. In a first ram retraction protocol (184a), a first ram may be partially retracted (232), followed by a full retraction of a second ram (234), followed by a completion of the retraction of the first ram (238). In a second ram retraction protocol (184b), a first ram may be partially retracted (252), followed by a partial retraction of a second ram (254), and sometime thereafter each of the first and second rams may be completely retracted (260, 262). In a third ram retraction protocol (184c), the first and second rams are simultaneously and partially retracted (272), and sometime thereafter each of the first and second rams are completely retracted (276). In a fourth ram retraction protocol (184d), the first and second rams are simultaneously and fully retracted (292) based upon a programmed input or the like.
