MR image-guided needle biopsies with a combination of augmented reality and MRI: A pilot study in phantoms and animals

The goal of this study was to adapt an augmented reality (AR) system to work next to a high-field (1.5 T) closed bore MR scanner (Magnetom Sonata, Siemens Medical Solutions, Erlangen, Germany) and to test its use as a navigation tool for MRI-guided needle biopsies. The AR system consists of a video-see-through head-mounted display with two color video cameras attached to the HMD that provide a stereoscopic view and a that is added for tracking. The tracking camera measures the viewer's position and orientation in relation to a set of optical markers on the MRI table. Gel phantoms with tube targets and multiple anatomic structures in two pigs were used as targets. For the biopsy phantom all punctures were inside the 6-mm diameter tube in the axial plane. The needle depth was within the target in 11 biopsies, 9 biopsies showed a slight deviation with a mean distance to the edge of the target slice of 1.5 mm. In the animals the puncture was successful in all 10 cases with a mean target-needle distance of 9.6 + 4.85 mm. The AR system presented here has proven to effectively facilitate image-guided percutaneous needle biopsies. MR images acquired shortly before the procedures are mapped into the patient space after moving the patient outside the magnet. This method provides a direct and intuitive way to perform percutaneous image-guided interventions with a closed bore MR scanner.