The fluid injection apparatus includes a syringe, an injector, and a pressure jacket. The syringe has a cylindrical body with an injection section at a distal end and a plurality of outward extending retaining flanges at a proximal end. The injector has an injector housing defining a central opening and an injector drive piston extendable through the central opening for imparting motive forces to a syringe plunger disposed within the syringe. The pressure jacket secures the syringe during an injection procedure. The pressure jacket has a wall defining a plurality of longitudinally extending grooves in an inner surface thereof configured to receive the retaining flanges of the syringe. The grooves cooperate with a plurality of transversely extending slots defined in the inner surface of the pressure jacket wall. The engagement of the retaining flanges in the slots via the grooves secures the syringe in the pressure jacket.