A fluid injection apparatus comprising: at least one pressurizing system; at least a first fluid path operably connectible to the at least one pressurizing system to transport fluid pressurized by the pressurizing system, the at least a first fluid path comprising a tubing set and a catheter; a control system operably associated with the at least one pressurizing system and comprising an input system, a user interface system, a processor system, and a memory system, the input system providing for input of an initial injection protocol of an injection procedure according to which at least one fluid is intended to be injected into a patient, and at least one model stored in the memory system and executable by the processor system to predict, before carrying out the initial injection protocol, if a pressure threshold value would be reached in the at least a first fluid path if the initial injection protocol were carried out, the at least one model determining if the pressure threshold value would be reached on the basis of a flow rate of the at least one fluid, at least one catheter characteristic, and a viscosity of the at least one fluid, the at least one model being determined experimentally for a plurality of fluids of different viscosities, for a plurality of catheters of different catheter characteristics, and for at least one tubing set of like kind to the tubing set of the first fluid path, upon determining via the at least one model that the pressure threshold value would not be reached, the processor system enabling the initial injection protocol to be carried out by the fluid injection apparatus, and upon determining via the at least one model that the pressure threshold value will be reached, the processor system either alerting an operator via the user interface system, whereupon the operator is enabled to choose between (a) permitting the initial injection protocol to be carried out by the fluid injection apparatus as programmed and (b) effecting a change to update the initial injection protocol for input into the at least one model or automatically effecting a change to update the initial injection protocol to create an updated injection protocol so that the expected pressure level will be determined via the at least one model to be less than or equal to the pressure threshold value thereby enabling the updated injection protocol to be used to introduce the at least one fluid into the fluid path. at least one pressurizing system; at least a first fluid path operably connectible to the at least one pressurizing system to transport fluid pressurized by the pressurizing system, the at least a first fluid path comprising a tubing set and a catheter; a control system operably associated with the at least one pressurizing system and comprising an input system, a user interface system, a processor system, and a memory system, the input system providing for input of an initial injection protocol of an injection procedure according to which at least one fluid is intended to be injected into a patient, and at least one model stored in the memory system and executable by the processor system to predict, before carrying out the initial injection protocol, if a pressure threshold value would be reached in the at least a first fluid path if the initial injection protocol were carried out, the at least one model determining if the pressure threshold value would be reached on the basis of a flow rate of the at least one fluid, at least one catheter characteristic, and a viscosity of the at least one fluid, the at least one model being determined experimentally for a plurality of fluids of different viscosities, for a plurality of catheters of different catheter characteristics, and for at least one tubing set of like kind to the tubing set of the first fluid path,