Fast 5DOF Needle Tracking in iOCT

TL;DR

This paper introduces a fast, robust method for tracking the 5-degree-of-freedom pose of a surgical needle in intraoperative OCT images, enabling real-time instrument localization without complex calibration.

Contribution

It presents a novel ellipse fitting and geometric modeling approach for 5DOF needle tracking directly in OCT space, improving robustness and speed over baseline methods.

Findings

Accurately estimates 5DOF needle pose in under 5.5 ms on CPU.

Maintains angular precision during lateral needle movements.

Outperforms baseline methods in robustness and consistency.

Abstract

Purpose. Intraoperative Optical Coherence Tomography (iOCT) is an increasingly available imaging technique for ophthalmic microsurgery that provides high-resolution cross-sectional information of the surgical scene. We propose to build on its desirable qualities and present a method for tracking the orientation and location of a surgical needle. Thereby, we enable direct analysis of instrument-tissue interaction directly in OCT space without complex multimodal calibration that would be required with traditional instrument tracking methods. Method. The intersection of the needle with the iOCT scan is detected by a peculiar multi-step ellipse fitting that takes advantage of the directionality of the modality. The geometric modelling allows us to use the ellipse parameters and provide them into a latency aware estimator to infer the 5DOF pose during needle movement. Results. Experiments on phantom data and ex-vivo porcine eyes indicate that the algorithm retains angular precision especially during lateral needle movement and provides a more robust and consistent estimation than baseline methods. Conclusion. Using solely crosssectional iOCT information, we are able to successfully and robustly estimate a 5DOF pose of the instrument in less than 5.5 ms on a CPU.