An angiographic injector (10), preferably in the form of a dual port syringe (78,80), has an upper port (78) for connection to a fluid reservoir (22) and a lower port (80) for delivery of the medical fluid under pressure to a patient. A first valve (24) is connected between the fluid reservoir (22) and the upper port (78), and a second valve (26) is connected between the lower port (80) and the patient. During a fill operation, a piston (20) is moved within the syringe (18) to draw fluid from the reservoir (22) into the syringe (18) through the first valve and the upper port. The first valve permits air to be expelled from the syringe through the first valve during a purge operation, but blocks flow of fluid from the syringe back to the fluid reservoir. During injection operation, the piston moves in an opposite direction to force fluid out of the syringe through the lower port.
