Figure 2. Illustrates how overlay of C-arm CT anatomy on top of conventional fluoroscopy may assist in catheter guidance. 3D structures of interest, in this case the left atrium, spine (S), and esophagus (E), were first segmented from the C-arm CT image and then displayed on top of the fluoroscopic image. Additional registration was not required because the C-arm CT was acquired with the same X-ray system as the live fluoroscopy. The underlying fluoroscopic image clearly depicts the ablation (C), lasso (L), and coronary sinus (CS) catheters, but contains minimal soft tissue detail. However, the location of the ablation catheter and lasso catheter within the left inferior PV is clear when anatomic structures from the C-arm CT are overlaid. In this study, ablation locations (A) could also be displayed with the C-arm CT data. (Adapted from Li, et.al. Heart Rhythm 2009).