1. In a medical imaging system having a behavior engine with behavior objects interconnected by parameters, at least one parameter being circularly dependent on another parameter, a method for handling a changed parameter for a given transaction comprising: changing at least one parameter; accessing a static list, the static list comprising the parameters and associated behavior objects; generating a dynamic list, based on the static list, of behavior objects dependent on the changed parameter; iteratively: processing the behavior objects in the dynamic list; determining whether any output parameters from the processed behavior objects have changed; adding behavior objects to the dynamic list which are dependent on the changed parameter outputs; and removing the processed behavior objects from the dynamic list.