Semi-Automatic Infrared Calibration for Integrating Augmented Reality Headsets with Surgical Tracking Systems

Core Concepts

A semi-automatic calibration system that enables the integration of augmented reality head-mounted displays, such as the Microsoft HoloLens 2, with surgical tracking systems used in computer-assisted orthopaedic surgery.

Abstract

The paper presents a calibration system that allows for the integration of augmented reality (AR) head-mounted displays (HMDs), specifically the Microsoft HoloLens 2, with surgical tracking systems used in computer-assisted orthopaedic surgery (CAOS). The key highlights are:

The system utilizes the infrared (IR) sensors and depth cameras on the HoloLens 2 to detect and track IR-reflective marker arrays that are commonly used in CAOS systems for tool and anatomy tracking. This eliminates the need for additional tracking infrastructure or custom calibration tools.

The calibration process is semi-automatic, where the user simply needs to look at a target array of IR markers visible to both the HoloLens 2 and the surgical robot's optical tracker. The system then calculates the spatial transformation between the HMD's virtual coordinate frame and the optical tracker's coordinate frame.

Experimental results show that the system can achieve relative tracking errors of 2.03 mm and 1.12° when calculating the pose between two static marker arrays. When using the calibration result to provide in-situ holographic guidance for a simulated wire-insertion task, the system reported mean errors of 2.07 mm and 1.54° compared to a pre-planned trajectory.

The proposed calibration approach is designed to be easily integrated with existing CAOS systems, as it does not require any modifications to the HMD or the introduction of new tracking infrastructure in the surgical scene. This makes it a practical solution for deploying AR-based guidance in computer and robot-assisted surgical workflows.

Stats

The system achieved a mean absolute relative tracking error of 2.028 mm for translation and 1.122° for rotation when calculating the pose between two static marker arrays.
When using the calibration result to provide in-situ holographic guidance for a simulated wire-insertion task, the system reported mean errors of 2.07 mm for translation and 1.54° for rotation compared to a pre-planned trajectory.

Quotes

"Successful deployment of AR to CAOS requires a calibration that can accurately calculate the spatial relationship between real and holographic objects."
"Our system aimed to facilitate easier integration of AR-HMDs with established CAOS systems, to simplify the deployment of AR in computer and robot-assisted surgical workflows, and to use clinically established optical trackers to guide in-situ positioning of holographic content."

Key Insights Distilled From

Semi-Automatic Infrared Calibration for Augmented Reality Systems in Surgery

by Hisham Iqbal... at arxiv.org 05-06-2024

https://arxiv.org/pdf/2405.01999.pdf

Deeper Inquiries

How could the system's performance be further improved to meet the clinical accuracy requirements for computer-assisted surgery

To enhance the system's performance to meet the stringent clinical accuracy requirements for computer-assisted surgery, several improvements can be implemented:

Enhanced Calibration Algorithms: Implement more sophisticated algorithms for calibration that can account for any potential drift or accumulated errors in the HoloLens's inside-out tracking system. This can help maintain the accuracy of the registration between the AR headset and the optical tracker over extended periods.

Real-time Error Correction: Introduce real-time error correction mechanisms that can continuously adjust for any discrepancies between the virtual and physical environments. This can help mitigate errors and ensure precise alignment during surgical procedures.

Advanced Sensor Fusion: Incorporate advanced sensor fusion techniques to combine data from multiple sensors, such as IR markers, depth sensors, and optical trackers, to improve the overall accuracy of the system. This can provide a more robust and reliable tracking mechanism.

Optimization for Dynamic Environments: Optimize the system to perform effectively in dynamic surgical environments where movements and changes occur frequently. This can involve refining the tracking algorithms to adapt to varying conditions without compromising accuracy.

Clinical Validation Studies: Conduct extensive clinical validation studies with real surgical scenarios and professionals to fine-tune the system based on feedback and performance evaluations in practical settings. This iterative process can help identify areas for improvement and ensure the system meets clinical standards.

What are the potential challenges and limitations of using inside-out tracking capabilities of AR headsets for surgical applications, and how could they be addressed

Using inside-out tracking capabilities of AR headsets for surgical applications presents several challenges and limitations that need to be addressed:

Limited Tracking Range: The 1-meter range limitation of the HoloLens's inside-out tracking system can restrict the freedom of movement for surgeons and may not cover the entire surgical field. This limitation could be addressed by exploring ways to extend the tracking range or implementing complementary tracking technologies for broader coverage.

Environmental Interference: Surgical environments can be complex, with various equipment, lighting conditions, and reflective surfaces that may interfere with the accuracy of inside-out tracking. Implementing robust algorithms to filter out environmental noise and optimize tracking performance in challenging conditions is essential.

Latency and Drift: Latency and drift in the tracking system can impact the real-time alignment of virtual and physical elements, leading to inaccuracies during surgical procedures. Minimizing latency and drift through software optimizations and sensor calibration can help improve the overall performance of the system.

User Training and Adaptation: Surgeons and medical staff may require training to effectively use AR headsets for surgical applications, especially in interpreting holographic guidance and integrating it into their workflow. Providing comprehensive training programs and user-friendly interfaces can help overcome this challenge.

Regulatory Compliance: Adhering to regulatory standards and ensuring the safety and efficacy of AR technology in surgical settings is crucial. Addressing regulatory requirements and obtaining necessary approvals are essential steps in integrating AR technology into medical practice.

What other medical or surgical domains beyond orthopaedics could benefit from the integration of augmented reality technology enabled by this calibration approach

Beyond orthopaedics, several other medical and surgical domains could benefit from the integration of augmented reality technology enabled by this calibration approach:

Neurosurgery: AR technology can assist neurosurgeons in visualizing complex brain structures, planning surgical paths, and navigating delicate procedures with enhanced precision and accuracy.

Cardiovascular Surgery: AR can provide real-time visualization of cardiac anatomy, aid in planning minimally invasive procedures, and guide surgeons during intricate cardiac surgeries, improving outcomes and patient safety.

Ophthalmology: AR applications can support ophthalmic surgeons in performing precise interventions, such as retinal surgeries and cataract procedures, by overlaying digital information onto the surgeon's field of view for enhanced guidance.

ENT (Ear, Nose, Throat) Surgery: AR technology can assist ENT surgeons in visualizing intricate structures in the head and neck region, facilitating precise navigation during procedures like endoscopic sinus surgery and cochlear implantation.

Plastic and Reconstructive Surgery: AR can aid plastic surgeons in preoperative planning, tissue reconstruction, and aesthetic procedures by providing 3D visualizations of patient anatomy and guiding surgical interventions with accuracy.

By leveraging the capabilities of AR technology and the calibration approach described, these medical specialties can benefit from improved visualization, enhanced surgical guidance, and optimized outcomes for patients.