Fig. 3.

A: The concept of Euclidean distance. The tip of the planned trajectory is represented by point P, and the tip of the actual electrode is represented by point Q. The arrow is the Euclidean distance between both points. B: The Euclidean distance formula. For two points, the coordinates x, y and z are determined, and the Euclidean distance is defined as the square root of the sum of the squares of the difference between these coordinates