This project will characterize the accuracy of a small magnetic tracking system and develop techniques to improve image-guided, minimally invasive spine interventions. Tracking systems are an integral part of image-guided surgery systems and allow the position of instruments to be followed in three-dimensional space. This new generation of magnetic trackers is well suited to less invasive, percutaneous spine interventions because of their small size. The accuracy of the magnetic tracking system will be compared with existing optical tracking systems using well-established engineering methods. New techniques and instrumentation will be developed for embedding these trackers in vertebral bodies and evaluated using an interventional phantom (Phase I) and animal models and cadavers (Phase II). It is anticipated that improved tracking systems for image guidance will enhance minimally invasive spine procedures and lead to decreased morbidity in these commonly performed interventions. Potential clinical applications include percutaneous interventions for low back pain and therapeutic treatments for spinal metastases. The commercial potential for these tracking systems is large, as the market for minimally invasive spine interventions has expanded dramatically in the past decade and is expected to continue to do so. The instrumentation developed here will be offered to computer assisted surgery (CAS) vendors for incorporation into their product lines.