An integrated MR imaging coil and body-mounted robot for MR-guided pediatric arthrography: SNR and phantom study

摘要

In this paper we report development of an integrated RF coil for our body-mounted arthrography robot called Arthrobot. Arthrography is the evaluation of joint conditions using imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI). Current arthrography practice requires two separate stages; an intra-articular contrast injection guided by fluoroscopy or ultrasound followed by MR imaging. Our body-mounted robot is intended to enable needle placement in the MRI environment, streamlining the procedure. To improve imaging with our robot, a single loop coil was created and embedded into the mounting adaptor of the robot. This coil provides enough spatial coverage and sensitivity to localize anatomical points of interest and registration fiducials on the robot frame. In this paper we report the results of a SNR and heating study using our custom-made RF coil in four different scenarios using T1 and T2 weighted MR images: 1) no robot present, 2) robot off, 3) robot powered on, and 4) robot running. We also report an end-to-end robotic-assisted targeting study in a Philips MRI scanner suite using Arthrobot and our custommade RF coil for image acquisition. The SNR results and targeting results were promising. SNR dropped 32% for T1 weighted images compared to baseline (no robot present) images. For T2 weighted images the SNR drop was 42%. The average targeting error was 2.91 mm with a standard deviation (SD) of 1.82 mm. In future work we plan to replace the passive fiducials embedded in the base of Arthrobot with active fiducials that are tracked by the MRI system. These active fiducials will enable real-time tracking of the robot base and could allow breathing motion compensation during robotic procedures.