A pressure jacket configured for removably connecting to an injector head of a fluid injector, the pressure jacket comprising: an open distal end, an open proximal end, and a sidewall defining a throughbore extending between the distal end and the proximal end along a longitudinal axis, the throughbore configured for receiving at least a portion of a syringe; at least one syringe retaining element is positioned at least partially within the throughbore; characterized in that wherein the at least one syringe retaining element engage at least a portion of a sidewall of the syringe during pressurized delivery of fluid from the syringe to prevent or limit a distal movement of the syringe relative to the pressure jacket by enhancing frictional forces between the interior surface of the sidewall of the pressure jacket and a pressure expanded sidewall of the syringe, thereby minimizing or eliminating a need for additional retention structures on the pressure jacket, and wherein the at least one syringe retaining element comprises at least one of: at least expansion pocket recessed radially outward into an interior surface of the sidewall of the pressure jacket, and the at least one syringe retaining element comprises at least one protrusion protruding radially inward from an interior surface of the sidewall of the pressure jacket, wherein a volume of the at least one expansion pocket or the radial protrusion of the at least one protrusion are selected such that expansion of the sidewall of the syringe into the at least one expansion pocket or the radial protrusion of the at least one protrusion into the sidewall of the syringe provide an axial restraining force to restrain movement of the syringe relative to the pressure jacket during the pressurized delivery of fluid from the syringe. an open distal end, an open proximal end, and a sidewall defining a throughbore extending between the distal end and the proximal end along a longitudinal axis, the throughbore configured for receiving at least a portion of a syringe; at least one syringe retaining element is positioned at least partially within the throughbore; characterized in that wherein the at least one syringe retaining element engage at least a portion of a sidewall of the syringe during pressurized delivery of fluid from the syringe to prevent or limit a distal movement of the syringe relative to the pressure jacket by enhancing frictional forces between the interior surface of the sidewall of the pressure jacket and a pressure expanded sidewall of the syringe, thereby minimizing or eliminating a need for additional retention structures on the pressure jacket, and wherein the at least one syringe retaining element comprises at least one of: at least expansion pocket recessed radially outward into an interior surface of the sidewall of the pressure jacket, and the at least one syringe retaining element comprises at least one protrusion protruding radially inward from an interior surface of the sidewall of the pressure jacket, wherein a volume of the at least one expansion pocket or the radial protrusion of the at least one protrusion are selected such that expansion of the sidewall of the syringe into the at least one expansion pocket or the radial protrusion of the at least one protrusion into the sidewall of the syringe provide an axial restraining force to restrain movement of the syringe relative to the pressure jacket during the pressurized delivery of fluid from the syringe. at least expansion pocket recessed radially outward into an interior surface of the sidewall of the pressure jacket, and the at least one syringe retaining element comprises at least one protrusion protruding radially inward from an interior surface of the sidewall of the pressure jacket, wherein a volume of the at least one expansion pocket or the radial protrusion of the at least one protrusion are selected such that expansion of the sidewall of the syringe into the at least one expansion pocket or the radial protrusion of the at least one protrusion into the sidewall of the syringe provide an axial restraining force to restrain movement of the syringe relative to the pressure jacket during the pressurized delivery of fluid from the syringe.