System and method for syringe plunger engagement with an injector

A plunger for use with a syringe, the plunger comprising:

• a plunger body defining a central longitudinal axis and having a proximal end, a distal end, and a circumferential sidewall connecting the proximal end and the distal end;
• and
• at least one retaining member associated with and extending proximally from the plunger body, the at least one retaining member comprising:
• a first end connected to the plunger body;
• a second end proximal to the first end and radially and resiliently deflectable relative to the first end;
• and
• at least one catch on the second end,
• wherein the at least one retaining member has an outer surface configured to engage a plunger engagement sleeve of a plunger engagement mechanism on a piston of a fluid injector system when the plunger is in a locked state with the piston,
• wherein the at least one retaining member has an inner surface configured to engage a plunger engagement post of the plunger engagement mechanism when the plunger is in the locked state with the piston,
• wherein the at least one catch is configured to fixedly engage a locking feature on one of the plunger engagement sleeve and the plunger engagement post when the plunger is in the locked state with the piston to prevent axial movement of the plunger relative to the piston,
• wherein the at least one catch has a first rounded or angled proximal surface at a proximal end of the at least one catch for flexibly engaging a distal end of the locking feature on one of the plunger engagement sleeve and the plunger engagement post during engagement of the plunger to the piston, and a second rounded or angled distal surface at a distal end of the at least one catch for flexibly engaging a proximal end of the locking feature on one of the plunger engagement sleeve and the plunger engagement post during disengagement of the plunger from the piston;
• and
• wherein in an unlocked state of the plunger engagement mechanism the first rounded proximal surface and the second rounded distal surface of the at least one catch are configured to radially deflect the second end of the at least one retaining member upon axial movement of the piston relative to the plunger due to a flexing interaction of the at least one catch with the locking feature on one of the plunger engagement sleeve and the plunger engagement post.