Process of MRI-US Fusion. MR and TRUS images are outlined or segmented (1) and then rigidly aligned (2). Fusion then proceeds involving a surface registration (3), and elastic (non-rigid) interpolation (4). Finally, the registered, or superimposed images are produced on a monitor, where targeted biopsy is performed. The target is derived from the MRI; the biopsy aiming is via real-time ultrasound13.From Natarajan S, Marks LS, Margolis DJ, et al. Clinical application of a 3D ultrasound-guided prostate biopsy system. Urologic oncology. May-Jun 2011;29(3):334-342; with permission.