Real‐time probe tracking using EM‐optical sensor for MRI‐guided cryoablation

Abstract

Background: A method of real-time, accurate probe tracking at the entrance of the MRI bore

Kalman filter-based EM-optical sensor fusion for needle deflection estimation

“…The results demonstrated the possibility to integrate an EM sensor into image-guided surgery with intraoperative MRI. Although replacing the EM sensor with another optical sensor may also allow the needle deflection estimation using our approach, but this EM sensor is crucial in our overall setup because we rely on the EM sensor to complete the final insertion inside the MRI bore when optical tracker fails due to line-of-sight issue [9].…”

“…Mala et al [6] have shown that in 28% of the cases, cryoablation of liver metastases was inadequate due to improper placement of the needles and unfavorable tumor locations. Therefore, we plan to develop a navigation system aimed at providing real-time guidance for accurate needle placement based on a two-stage scheme using both EM and optical tracker [9]. Nevertheless, as the clinicians maneuver the needle to the target location, the needle is likely to bend due to tissue inhomogeneity, tissue–needle or hand–needle interaction, fluid flow and respiration, resulting in an error in estimating the tip position [2].…”

“…We take advantage of an optical tracker at the needle’s base and an MRI gradient field-driven EM tracker attached to the shaft of the needle [17]. We adopt this dual-sensor approach to overcome the limitations of the individual sensors—noisy measurements of the EM sensor at the entrance of MRI scanner and line-of-sight problem of optical sensor [9]. By integrating the measurements from both sensors with either the angular springs model presented by Goksel et al [18] or the quadratic kinematic bending model used in [15,19], the Kalman filter-based fusion model is established to estimate the needle deflection in real time.…”