Some injectors of the invention may include a fluid drive responsive to pressure of a working fluid (e.g., liquid, pneumatic, or both) to impart a sequence of forces to drive a delivery device (e.g., a syringe) to deliver a medical fluid (e.g., a contrast agent, a radiopharmaceutical, a drug, or a combination thereof). Some injectors may include a multimedia tube configured to pass a working fluid (e.g., air) and a light signal (e.g., infrared). Some injectors may include a peristaltic drive responsive to pressure of a working fluid.