System and method having transition phase in multi-phase injection protocol

A method of delivering a multi-phase fluid injection to a patient via a fluid injector comprising two or more fluid reservoirs, the method comprising:

• injecting a first fluid of the multi-phase fluid injection from at least a first fluid reservoir, the first fluid having a first viscosity, wherein the first fluid is delivered to the patient at a first predetermined flow rate;
• injecting an initial portion of at least a second fluid of the multi-phase fluid injection during a transition phase from at least a second fluid reservoir configured to contain the second fluid of the multi-phase fluid injection, the second fluid having a second viscosity different from the first viscosity, wherein the initial portion of the second fluid is delivered to the patient with a flow rate profile different from a second predetermined flow rate for a specified intermediate time interval, wherein a control device calculates an intermediate flow rate profile before controlling the second drive member to inject the initial portion of the second fluid, wherein the specified intermediate time is selected to allow a residual portion of the first fluid to pass through a fluid line to the patient so that the residual portion of the first fluid is purged from the fluid line by the end of the specified intermediate time before beginning to inject a remaining portion of the second fluid, and wherein the specified intermediate time is based on a system architecture, a capacitance of at least one of the first fluid reservoir or the second fluid reservoir, a length of the fluid line, a diameter of the fluid line, a volume of the fluid line, a length of a catheter, a diameter of the catheter, a volume of the catheter, or any combination thereof;
• and
• injecting the remaining portion of the second fluid of the multi-phase fluid injection at a flow rate at least equal to the second predetermined flow rate directly after the injection of the initial portion of the second fluid,
• wherein a volume of the initial portion of the second fluid of the multi-phase fluid injection is determined by one or more of a volume capacity of the fluid line between the at least one second fluid reservoir and the patient, the capacitance of at least one of the at least one first fluid reservoir and the at least one second fluid reservoir, and injector system compliance, wherein the at least one first fluid reservoir is selected from the group consisting of a first syringe, a first peristaltic pump, and a first compressible bag, and wherein the at least one second fluid reservoir is selected from the group consisting of a second syringe, a second peristaltic pump, and a second compressible bag.