A Single-Fiber Optical Frequency Domain Reflectometry (OFDR)-Based Shape Sensing of Concentric Tube Steerable Drilling Robots
Yash Kulkarni, Mobina Tavangarifard, Daniyal Maroufi, Mohsen Khadem, Justin E. Bird, Jeff Siewerdsen, Farshid Alambeigi
AI summary
Problem
Current steerable drilling robots lack reliable, high-resolution shape sensing due to the fabrication complexity, spatial resolution limits, and environmental vulnerability of conventional fiber Bragg grating (FBG) sensors. This gap hinders precise trajectory tracking during minimally invasive spinal fixation surgery.
Approach
The authors fabricated a Shape Sensing Assembly (SSA) by bonding a single OFDR fiber to a flat NiTi wire and routed it through the internal channel of a flexible drilling instrument within a cannulated Concentric Tube Steerable Drilling Robot (CT-SDR). This configuration uses the drill as a protective sheath while enabling continuous strain measurement and real-time shape reconstruction.
Key results
- Successful fabrication and calibration of a single-fiber OFDR SSA with a flat NiTi substrate
- Integration of the SSA within a cannulated CT-SDR using the drill instrument as a protective sheath
- Accurate shape reconstruction during free-bending tests with low average tip and shape errors
- Reliable trajectory tracking and shape sensing during drilling in synthetic bone phantoms along J-shaped paths
Why it matters
Enables safer, more precise minimally invasive spinal surgery by providing surgeons with real-time, high-resolution robot shape feedback without radiation exposure or line-of-sight constraints.
Abstract
This paper introduces a novel shape-sensing ap- proach for Concentric Tube Steerable Drilling Robots (CT- SDRs) based on Optical Frequency Domain Reflectometry (OFDR). Unlike traditional FBG-based methods, OFDR enables continuous strain measurement along the entire fiber length with enhanced spatial resolution. In the proposed method, a Shape Sensing Assembly (SSA) is first fabricated by integrating a single OFDR fiber with a flat NiTi wire. The calibrated SSA is then routed through and housed within the internal channel of a flexible drilling instrument, which is guided by the pre-shaped NiTi tube of the CT-SDR. In this configuration, the drilling instrument serves as a protective sheath for the SSA during drilling, eliminating the need for integration or adhesion to the instrument surface that is typical of conventional optical sensor approaches. The performance of the proposed SSA, integrated within the cannulated CT-SDR, was thoroughly evaluated under free-bending conditions and during drilling along multiple J- shaped trajectories in synthetic Sawbones phantoms. Results demonstrate accurate and reliable shape-sensing capability, confirming the feasibility and robustness of this integration strategy.