Fast and automatic depth control of iterative bone ablation based on optical coherence tomography data

Abstract

Laser surgery is an established clinical procedure in dental applications, soft tissue ablation, and ophthalmology. The presented experimental set-up for closed-loop control of laser bone ablation addresses a feedback system and enables safe ablation towards anatomical structures that usually would have high risk of damage.This study is based on combined working volumes of optical coherence tomography (OCT) and Er:YAG cutting laser. High level of automation in fast image data processing and tissue treatment enables reproducible results and shortens the time in the operating room. For registration of the two coordinate systems a cross-like incision is ablated with the Er:YAG laser and segmented with OCT in three distances. The resulting Er:YAG coordinate system is reconstructed. A parameter list defines multiple sets of laser parameters including discrete and specific ablation rates as ablation model. The control algorithm uses this model to plan corrective laser paths for each set of laser parameters and dynamically adapts the distance of the laser focus. With this iterative control cycle consisting of image processing, path planning, ablation, and moistening of tissue the target geometry and desired depth are approximated until no further corrective laser paths can be set. The achieved depth stays within the tolerances of the parameter set with the smallest ablation rate. Specimen trials with fresh porcine bone have been conducted to prove the functionality of the developed concept. Flat bottom surfaces and sharp edges of the outline without visual signs of thermal damage verify the feasibility of automated, OCT controlled laser bone ablation with minimal process time.

Deep-learning-based 2.5D flow field estimation for maximum intensity projections of 4D optical coherence tomography

“…The spatial control of the laser requires intraoperative navigation and registration from OCT to ablation laser and OCT to patient. 5,6 In addition to the use of external optical navigation, which makes the process even more complex, OCT itself can be used as high-precision navigation system for tracking relative motion between the laser target area and the joint system consisting of ablation laser and OCT (AL-OCT). OCT as optical tracking system has already been addressed.…”

Quantitative Evaluation of the Thickness of the Available Manipulation Volume Inside the Knee Joint Capsule for Minimally Invasive Robotic Unicondylar Knee Arthroplasty

“…Laser osteotomy offers a low contact force alternative to cutting bone with conventional mechanical tools [23]. In addition, cutting with a laser has been shown to result in faster bone healing, higher cutting precision, improved cutting-depth control [24], and increased freedom in the cutting geometry compared to cutting with mechanical tools [25]. Our device will consist of a flexible robotic endoscope inserted into the knee joint through a small incision (Fig.…”

Concept for high speed vocal cord imaging with swept-source optical coherence tomography

“…The superficial and deep layers of the lamina propria should be preserved to prevent scarring. 2 Depth-controlled laser cutting is possible with utilization of optical coherence tomography (OCT) 3 and could be used to avoid this issue. Due to the relatively slow acquisition speed of conventional OCT systems, OCT cross-sectional images, so called B-scans, of vibrating vocal cords suffer from motion artifacts.…”