1. A method for instrument placement using an image based navigation system comprising the steps of: displaying, in a three dimensional image, an image plane that goes through a center of a target of interest, the image plane having a configurable orientation; receiving user input configuring an orientation of an instrument; displaying, in the three dimensional image, a trajectory plane from the tip of the instrument to the center of the target, the trajectory plane reflecting a current orientation of the instrument and intersecting the image plane at the center of the target of interest, wherein the image plane is orthogonal to a direction of instrument insertions; displaying in the trajectory plane, the target of interest and potential obstacles in a path for the instrument from a position on a patient's skin to the center of the target; displaying in the trajectory plane a virtual extended path of the instrument from a point that a tip of the instrument is in contact with the patient's skin to the center of the target, the virtual extended path based on the current orientation of the instrument; receiving input selecting a particular trajectory plane representative of a desired orientation of the instrument; and freezing an image of the particular trajectory plane.