The development of the graphics hardware in the last few years made them much faster. This brings new possibilities for complex visualizations in real-time. One application where a real-time visualization is very important is the interventional imaging for minimal-invasive surgeries. Thereby the physician has to do the surgery based on the provided visualization. In this book a new, complex technique is described which improves this visualization by integrating the pre-operative data, such as CT, directly in the final visualization together with the image from the interventional imaging system, such as ultrasound. The benefit of this technique is that the physician has all important information directly at the intervention. Besides the technique itself the book gives an overview on related techniques in medical visualization and describes how the new technique can be implemented on graphics hardware. In a result section images for the special medical application of liver biopsy are shown. This book is mainly for computer scientists with a focus on medical visualization but it can also be interesting for medical staff to see what happens before an image is showing up on the screen.