Wireless positional MR-based tracking markers for intraoperative MRI-guided robotic interventions

Abstract

In recent years, Magnetic Resonance Imaging (MRI) guided intervention plays an increasingly important role in reshaping the current interventional practice with CT or X-ray fluoroscopy. This is attributed to the unique advantages of MRI, such as zero ionizing radiation and high-contrast visualization of soft tissues and their physiological details. Despite the many benefits of MRI-guided interventional approaches, several difficulties inhibit its widespread use in clinical practice. The primary difficulty lies in the interaction of surgical instruments with the MRI system. Specifically, the strong static magnetic field inside the MRI bore disallows any localization device made with ferromagnetic materials, therefore limiting the choice of tracking approaches. The strong magnetic field also makes the design and fabrication of MR (magnetic resonance) conditional devices very complicated. Any improper electromagnetic (EM) signal generated during the MRI causes significant artifacts, which can distort and deteriorate overall image quality.

The main focus of this thesis is to develop novel sensor designs for miniaturizing tracking devices, and enabling omnidirectional tracking capability within a closed-bored MR scanner. Wireless MR-based positional tracking is a significant focus of this thesis, where a tetherless marker can provide real-time three dimensional positional data for robotic position feedback control. Two novel wireless marker designs were proposed with (i) multilayer stacked inductors, and (ii) monolithic curved circuits. Our studies have shown that the markers design can provide promising MR-tracking capability with high quality factor, small form factor with negligible orientational dependency. The marker can be made with high accuracy and repeatability through machine fabrication, and deploy on intraoperative devices and robot structures with real-time 3D positional tracking capability.