[Design, clinical suitability and future aspects of a 0.5 T MRI special system for interventional use].

Purpose: To develop a superconducting magnetic resonance (MR) imager that provides direct access to the patient and permits interactive MR-guided interventional procedures.
Materials and Methods: A 0.5-T superconducting magnet that allows a region of vertical access to the patient was designed and constructed. This magnet was integrated with newly designed shielded gradient coils, flexible surface coils, nonmagnetic displays, position-monitoring probes and device-tracking instrumentation.
Results: The magnet homogeneity was 12.3 ppm or better, and the gradient field was linear to within 1% over an imaging region of 30 cm in diameter. The signal-to-noise ratio was 10% higher than in a comparable 0.5-T superconducting imager. Images were obtained in several anatomic regions with use of routine pulse sequences. Interactive image plane selection and near real-time imaging, with use of fast gradient-recalled echo sequences were demonstrated at a rate of one image every 1.5 s. More than 240 procedures (including open brain surgery) have been successfully performed within this environment.
Conclusions: MR-guided interventional and surgical procedures can be performed with full patient access using an open-configuration, superconducting MR magnet with near real-time imaging and interactive image plane control.