Abstract: The pressure jacket systems of the invention are used to permit the front loading and removal of a syringe from an injector and include a first jacket segment and a second jacket segment surrounding the exterior surface of the syringe, interior surfaces comformable to the exterior surface of the syringe, a mechanism which allows movement of the first jacket segment in relation to the second jacket segment to permit insertion and removal of the syringe from the pressure jacket, and a mechanism for securing the first and second jacket segments in a fixed relationship upon insertion of the syringe.