Concept for Markerless 6D Tracking Employing Volumetric Optical Coherence Tomography.

Matthias Schlüter,Lukas Glandorf,Alexander Schlaefer,Thore Saathoff,Martin Gromniak

doi:10.3390/s20092678

Matthias Schlüter, Lukas Glandorf + Show 3 more

Open Access

https://doi.org/10.3390/s20092678

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Abstract

Optical tracking systems are widely used, for example, to navigate medical interventions. Typically, they require the presence of known geometrical structures, the placement of artificial markers, or a prominent texture on the target’s surface. In this work, we propose a 6D tracking approach employing volumetric optical coherence tomography (OCT) images. OCT has a micrometer-scale resolution and employs near-infrared light to penetrate few millimeters into, for example, tissue. Thereby, it provides sub-surface information which we use to track arbitrary targets, even with poorly structured surfaces, without requiring markers. Our proposed system can shift the OCT’s field-of-view in space and uses an adaptive correlation filter to estimate the motion at multiple locations on the target. This allows one to estimate the target’s position and orientation. We show that our approach is able to track translational motion with root-mean-squared errors below 0.25 mm and in-plane rotations with errors below 0.3°. For out-of-plane rotations, our prototypical system can achieve errors around 0.6°.

Highlights

Optical tracking is an established approach in a wide range of applications to estimate or compensate the motion of a target
The calibration positions are located at three discrete radii within the cylindric volume, and Figure 7 shows the residual error of the calibration procedure depending on the radius
We showed that 6D motion tracking with volumetric optical coherence tomography (OCT) is feasible

Summary

Introduction

Optical tracking is an established approach in a wide range of applications to estimate or compensate the motion of a target. To reduce the likelihood of such situations, different approaches to immobilize the head can be employed; for example, stereotactic frames or thermoplastic masks. There is always some residual motion in the case of masks For these reasons, head tracking is an important approach, especially because systems like the CyberKnife (Accuray) allow one to dynamically adjust the direction of the treatment beams. Head tracking is an important approach, especially because systems like the CyberKnife (Accuray) allow one to dynamically adjust the direction of the treatment beams This requires continuous tracking of the head’s pose with high accuracy and low latency. Markerless approaches to this task employ, for example, structured light [3] or time-of-flight cameras [4]. Another application for head tracking in Sensors 2020, 20, 2678; doi:10.3390/s20092678 www.mdpi.com/journal/sensors

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