Fig. 3.

Representation of the needle inside the prostate, illustrating targeting error (ε), target displacement (φ) and biopsy error (δ). The targeting error, defined as the normal distance from needle to the original target coordinate (T), is shown. Target displacement, defined as the distance between original target (T) and transformed target (T′), is represented by φ. Furthermore, the biopsy error (δ) is shown, which is defined as the normal distance between transformed target (T′) and needle