Background
The past years showed a considerable progress in the development of imaging and navigation systems to support minimal-invasive surgery. However, these methods do not always meet actual clinical requirements of surgeons. They often cause technical and logistic efforts and considerable costs. Purpose of our study was the development of a navigation system relying on simple, familiar and cheaper components. It is based on two-dimensional ultrasound visualization, is quickly applicable to a wide range of minimal-invasive interventions, and is easily to be learned.
Material and Method
The imaging system is composed of widely used, well-accepted components and relies only upon conventional two-dimensional sonography using a navigated ultrasound probe, a navigated surgical instrument, and a coordinate tracker, combined with new custom-made navigation software. Accuracy tests were performed, possible error sources were mentioned and the easy and safe handling of this system was demonstrated.
Results
Our custom-made software integrates information about the three-dimensional position of an instrument into a two-dimensional ultrasonic image. On-screen navigation aids are offered to reach a sonographically depicted target structure. These navigation aids are easily to be learned and make the use of this system very comfortable. The system shows a mean three-dimensional error of only 0.9+/-0.2 mm.
Conclusions
Our navigation system combines several advantages: as to visualization, it relies solely on the familiar two-dimensional ultrasound image, its use is easy, it is more economic than comparable ultrasound navigation systems, and it can be used in a wide range of minimal-invasive interventions.

Keywords: Surgical Procedures, Minimally Invasive - instrumentation, Calibration, Ultrasonics