1. A system for estimating within a 2D space a position in an x-ray projection image corresponding to a projected position of an intravascular probe in a vascular system at a time of acquiring data from the intravascular probe, the system comprising: an x-ray detector configured to, acquire a 2D x-ray projection image; and a processor coupled to a memory wherein the memory configures the processor to identify in the 2D x-ray projection image utilizing the 2D space, a projected position of a plurality of markers located at predetermined distances along a trajectory of the intravascular probe, and interpolate within the 2D space the projected position of the intravascular probe on the trajectory corresponding to a location within the 2D x-ray projection image of the intravascular probe at a time of acquiring the data which is a different time then when the 2D x-ray projection image is acquired, dependent on a distance along the trajectory between the intravascular probe at the time of acquiring the data and at least one of the markers along the trajectory.