Recording Hand-Held Laparoscopic Instrument Motion in the Operating Room: Magnetometer-Free Fusion of Inertial, Range and Visual Sensing

Jiyul Lee, Dongho Yee, Juahn Oh, Jinseok Lee, Yechan Seo, Seong Jeong, Minsung Kim, Seonho Shim, Younghoon Noh, Hyuk Choi, Youngbin Kong, Hyoun-Joong Kong · N/A · 2026

Summary

Abstract Summary

Most minimally invasive procedures are still performed with hand-held laparoscopic instruments, yet only the endoscopic video is retained; the instrument motion that expresses surgical skill, and that could support skill assessment and robot learning, is lost. Pose from video alone remains millimeters to centimeters off, and an instrument-mounted inertial measurement unit (IMU) cannot rely on its magnetometer, whose field changed with tool pose and between sessions in our measurements. We present a surgical instrument-state logger that clips onto a conventional instrument without modifying the part that enters the patient and fuses a six-axis IMU and a time-of-flight (ToF) rangefinder with a markerless camera in an error-state Kalman filter under the remote center of motion (RCM) of the trocar. Heading comes from the shaft silhouette, segmented by a U-Net, in place of the magnetometer: the rotation-angle error is 0.200{\deg}, against 3.58{\deg} from the accelerometer and magnetometer alone. Against a Franka Research 3 manipulator, and without alignment to it, the displacement error over 300 translation trials was 1.21mm RMS and the relative-rotation error over 180 rotation trials 0.34{\deg} RMS. On continuous trajectories, tracked and displayed in real time, the absolute tip error was 1.22mm (programmed) and 3.04mm (teleoperated) after post-hoc tuning of three filter parameters, and the full fusion beat every sensor subset. Because the estimator uses no magnetic measurement, its accuracy does not rely on an undisturbed field. The same clip-on device could thus record metric tip trajectories during routine hand-held laparoscopy, while displaying the insertion depth and attitude that are hidden once the instrument is inside the patient.

Key Points

Most minimally invasive procedures are still performed with hand-held laparoscopic instruments, yet only the endoscopic video is retained; the instrument motion that expresses surgical skill, and that could support skill assessment and robot learning, is lost.
Pose from video alone remains millimeters to centimeters off, and an instrument-mounted inertial measurement unit (IMU) cannot rely on its magnetometer, whose field changed with tool pose and between sessions in our measurements.
We present a surgical instrument-state logger that clips onto a conventional instrument without modifying the part that enters the patient and fuses a six-axis IMU and a time-of-flight (ToF) rangefinder with a markerless camera in an error-state Kalman filter under the remote center of motion (RCM) of the trocar.
Heading comes from the shaft silhouette, segmented by a U-Net, in place of the magnetometer: the rotation-angle error is 0.200{\deg}, against 3.58{\deg} from the accelerometer and magnetometer alone.
Against a Franka Research 3 manipulator, and without alignment to it, the displacement error over 300 translation trials was 1.21mm RMS and the relative-rotation error over 180 rotation trials 0.34{\deg} RMS.

Methods

This section covers the device and the trocar geometry, the preliminary study that rules the magnetometer out, the vision and range models, and the filter that fuses them. Table II lists which sensor fixes which degree of freedom. Their weaknesses are complementary: the gyroscope drifts, gravity is corrupted by motion, vision is intermittent and late, and ToF must be interpreted through the orientation.

The module clamps to the handle side of a standard laparoscopic instrument of 5.18 mm shaft diameter (Fig. 2 a).

Methods — Recording Hand-Held Laparoscopic Instrument Motion in the Operating Room: Magnetometer-Free Fusion of Inertial, Range and Visual Sensing — Fig. 2: The logger and the bench. (a) The clip-on module on the handle side of a standard instrument. (b) The FR3 holds it through the trocar of the phantom, the camera above the field. (c) Teleoperated recording with a haptic stylus and the live display.

Experiments

All experiments are referenced to an FR3 that holds the instrument through the trocar of the phantom (Fig. 2 b), and none of them lets robot data into the estimator: we evaluate static stability, observation latency, translation, rotation and continuous tracking, with sensor ablations throughout. Motions are commanded as minimum-jerk profiles about the RCM.

Sources and Demonstrations

Figures are reproduced from Lee et al. See the full paper for experimental details and the project page, when the paper links one, for demonstrations and videos.