A medical fluid injector comprising: an injector housing; at least one syringe port in the injector housing for receiving a proximal portion of a syringe; and a locking mechanism associated with the at least one syringe port for releasably locking the syringe within the at least one syringe port by releasably engaging at least one syringe retaining member of the syringe, the locking mechanism comprising: a locking ring rotatable between a first locked position and a second insertion/removal position for insertion or removal of the syringe from the locking mechanism; a biasing mechanism for biasing the locking ring in the first locked position; at least one second guide member on the locking ring, the at least one second guide member having a ramp surface for interacting with the at least one syringe retaining member of the syringe to rotate the locking ring from the first locked position to the second insertion/removal position as the syringe is inserted into the at least one syringe port; characterized in that the locking mechanism further comprises at least one sensor for detecting an angular position of the locking ring based on an orientation of a sensor pickup on the locking ring relative to the at least one sensor, wherein the at least one sensor is configured to detect whether the locking ring is in the first locked position, the second insertion/removal position, or a position between the first locked position and the second insertion/removal position; and a barcode reader system for reading at least one identification tag on the proximal portion of the syringe when the syringe is locked in the at least one syringe port. an injector housing; at least one syringe port in the injector housing for receiving a proximal portion of a syringe; and a locking mechanism associated with the at least one syringe port for releasably locking the syringe within the at least one syringe port by releasably engaging at least one syringe retaining member of the syringe, the locking mechanism comprising: a locking ring rotatable between a first locked position and a second insertion/removal position for insertion or removal of the syringe from the locking mechanism; a biasing mechanism for biasing the locking ring in the first locked position; at least one second guide member on the locking ring, the at least one second guide member having a ramp surface for interacting with the at least one syringe retaining member of the syringe to rotate the locking ring from the first locked position to the second insertion/removal position as the syringe is inserted into the at least one syringe port; characterized in that the locking mechanism further comprises at least one sensor for detecting an angular position of the locking ring based on an orientation of a sensor pickup on the locking ring relative to the at least one sensor, wherein the at least one sensor is configured to detect whether the locking ring is in the first locked position, the second insertion/removal position, or a position between the first locked position and the second insertion/removal position; and a barcode reader system for reading at least one identification tag on the proximal portion of the syringe when the syringe is locked in the at least one syringe port. a locking ring rotatable between a first locked position and a second insertion/removal position for insertion or removal of the syringe from the locking mechanism; a biasing mechanism for biasing the locking ring in the first locked position; at least one second guide member on the locking ring, the at least one second guide member having a ramp surface for interacting with the at least one syringe retaining member of the syringe to rotate the locking ring from the first locked position to the second insertion/removal position as the syringe is inserted into the at least one syringe port; characterized in that the locking mechanism further comprises at least one sensor for detecting an angular position of the locking ring based on an orientation of a sensor pickup on the locking ring relative to the at least one sensor, wherein the at least one sensor is configured to detect whether the locking ring is in the first locked position, the second insertion/removal position, or a position between the first locked position and the second insertion/removal position; and a barcode reader system for reading at least one identification tag on the proximal portion of the syringe when the syringe is locked in the at least one syringe port.