A power injector (154) is disclosed that may utilize decay constant determination logic (192). This logic (192) in turn may incorporate a test injection protocol (194). The test injection protocol (194) may be executed to acquire data for the derivation of a flow rate decay constant. The derived flow rate decay constant may be used by the power injector (154) to execute of an injection protocol (162), for instance in conjunction with an operation of an imaging unit (152) for an imaging operation.
