Feasibility of scan plane tracking using in-bore RGB-D camera(s) for online interventional MRI

Optical navigation systems have been proven useful for image-guided surgeries in clinical settings. Most of the optical sensors track precise locations of landmarks on surgical instruments and thus are costly, limiting its widespread adoption. Magnetic Resonance Imaging (MRI) is not only excellent in soft tissue contrast but also has the capability of unrestricted multiplanar imaging.

This study aims to develop an affordable navigation method for MRI-guided interventions by utilizing an in-bore consumer-grade RGB-D camera.

We utilize the camera to track a flat plane pad that is fixed parallel to the surgical tool, typically a needle. This simplifies the navigation process by focusing on locating a scan plane that fully encompasses the needle within the field of view of the MR image, allowing for greater tolerance to tracking deviations. The total cost of the hardware is less than $500.

Our proposed method was deployed in a C-shape 0.35T MRI system. The electromagnetic compatibility after integrating the camera was validated by measuring both magnetic field $B_0$ homogeneity and image signal-to-noise ratio. In needle-plane tracking experiments, the RGB-D based tracking method demonstrated a maximum distance error of $1.32\pm 0.41$  mm and a maximum angular error of $1.{69}^{\circ }\pm 0.{18}^{\circ }$ . Additionally, we simulated ex vivo pig liver biopsy, demonstrating the navigation feasibility of our method in combination with online MRI.

Overall, we pioneer a novel RGB-D camera navigation system that makes MRI-guided interventions more accessible in clinical practice at a much lower cost.