In general, this disclosure relates to techniques for sealing, or pinching, high-pressure fluid tubing (e.g., braided tubing) that may be used to deliver medical fluid from a powered medical fluid injection device, such as an injector that delivers contrast media and/or saline during angiographic or computed tomography (CT) procedures. In some cases, one or more low-friction, solenoid-based pinch valve mechanisms may be used. One example powered medical fluid injection device comprises an injector head and at least one pinch valve mechanism that is coupled to the injector head. The at least one pinch valve mechanism comprises a plunger, a reciprocating arm driven by the plunger, and a tube pinching area. The at least one pinch valve mechanism, when deactivated by the injector head, is configured to cause the reciprocating arm to pinch fluid tubing that runs through the tube pinching area.