OCT-guided laser bone ablation for spinal surgery: an in-line deep learning approach for residual bone thickness monitoring

Abstract

Laser bone ablation is a promising, less-invasive alternative to mechanical drilling for spinal surgery, but its adoption requires precise, in-line depth control to prevent iatrogenic injury. We propose a deep learning-based feedback system using intraoperative optical coherence tomography (OCT). A U-Net++ architecture with an SE-ResNeXt-50 encoder was trained for inline semantic segmentation of B-scans from a Fourier-Domain OCT (FD-OCT) system with a 1550 nm central wavelength, accurately identifying remaining cortical bone thickness in a clinically relevant range of 50 to 1000 micrometers. The model leverages encoders pretrained on the NASA MicroNet dataset to enhance feature extraction in the microscopy domain. Trained and validated on experimental OCT data from a single ex vivo bovine femur specimen, the system serves as a proof-of-concept for few-shot transfer learning. Our approach achieves high segmentation accuracy, with a Dice Similarity Coefficient (DSC) of 0.984±0.010 and an Average Symmetric Surface Distance (ASSD) demonstrating sub-pixel accuracy (< 16 μm). With a processing speed exceeding 20,000 A-scans per second, the system meets demanding real-time surgical requirements. This method enables robust, automated process monitoring for safer OCT-guided laser spinal surgery.

Authors 7

1. David Jänsch Aachen Fraunhofer Institute for Laser Technology ILT

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer Institute for Laser Technology ILT (Germany)

2. Milena Žurić Aachen Fraunhofer Institute for Laser Technology ILT

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer Institute for Laser Technology ILT (Germany)

3. Christina Giesen Aachen Fraunhofer Institute for Laser Technology ILT

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer Institute for Laser Technology ILT (Germany)

4. Fabian Wendt Aachen Fraunhofer Institute for Laser Technology ILT

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer Institute for Laser Technology ILT (Germany)

5. Lazar Bochvarov Aachen Fraunhofer Institute for Laser Technology ILT

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer Institute for Laser Technology ILT (Germany)

6. G. Meineke Aachen Fraunhofer Institute for Laser Technology ILT

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer Institute for Laser Technology ILT (Germany)

7. Achim Lenenbach Aachen Fraunhofer Institute for Laser Technology ILT

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer Institute for Laser Technology ILT (Germany)