An Optical and Electromagnetic Hybrid Tracking System for MR Image Guided Interventional Procedures

INTRODUCTION In MR guided interventional procedures, image planes are required to include the needle path accurately. For the purpose, an optical or electromagnetic tracking system has been used. The optical tracking system precisely works in the strong magnetic fields, but line of sight must be maintained. Surgical procedure and instruments easily obstruct the light path and applicable angles are limited. An electromagnetic tracking system, which utilizes gradient pulses during data collection, can be used in any directions and even in the covered area, but it requires continuous MR image acquisitions to obtain the latest information. The accuracy of its information is decreasing at magnet center, where the changes in the magnetic strength by gradients are small, and at the periphery, where the gradients are not linear. They have advantages and disadvantages. To take advantages of two sensor systems complementarily, we have developed a hybrid tracking system of them for MR guided interventional procedures with an open configuration MR system.