62-Year old male presenting with a large circumflex artery to coronary sinus fistula near right atrium. The largest diameter measures 4cm which is about ten times larger than normal size. Curve Planar Reformations (CPR) demonstrates the beginning and ending of the fistula. The Volume Rendering (VR) images show the relationship and scale to other surrounding structures. Stanford 3DQ Lab technologists utilize 3D software tools to produce the valuable information and measurements in assisting with decision making of clinical diagnosis and treatment planning.