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Virtual Fluoroscopy for Interventional Guidance using Magnetic Tracking

Shuwei Xing, Inaara Ahmed-Fazal, Utsav Pardasani, Uditha Jayarathne, Scott Illsley, Aaron Fenster, Terry M. Peters, Elvis C. S. Chen

TL;DR

This work tackles depth perception and radiation exposure in fluoroscopy-guided interventions by introducing a virtual fluoroscopy workflow that integrates magnetic tracking with a radiolucent field generator. It combines automatic fluoro-CT registration, 2D-3D landmark correspondence, and a generalized C-arm pose model to render virtual views with real-time instrument overlays, enabling multiplanar visualization without excessive C-arm repositioning. Validation shows a mean 2D projection distance of about $1.55$ mm for simulated views and a needle-tip error around $3.42$ mm in phantom trials, with high frame-rate performance (e.g., ~38 fps for landmark detection and ~1.97 s per fluoro-CT registration) indicating real-time feasibility. The results suggest that MT-enabled virtual fluoroscopy can improve depth perception, reduce unnecessary fluoroscopy acquisitions, and facilitate more efficient interventional navigation, with future work focusing on broader clinical validation and workflow optimization.

Abstract

Purpose: In conventional fluoroscopy-guided interventions, the 2D projective nature of X-ray imaging limits depth perception and leads to prolonged radiation exposure. Virtual fluoroscopy, combined with spatially tracked surgical instruments, is a promising strategy to mitigate these limitations. While magnetic tracking shows unique advantages, particularly in tracking flexible instruments, it remains under-explored due to interference from ferromagnetic materials in the C-arm room. This work proposes a virtual fluoroscopy workflow by effectively integrating magnetic tracking, and demonstrates its clinical efficacy. Methods: An automatic virtual fluoroscopy workflow was developed using a radiolucent tabletop field generator prototype. Specifically, we developed a fluoro-CT registration approach with automatic 2D-3D shared landmark correspondence to establish the C-arm-patient relationship, along with a general C-arm modelling approach to calculate desired poses and generate corresponding virtual fluoroscopic images. Results: Testing on a dataset with views ranging from RAO 90 degrees to LAO 90 degrees, simulated fluoroscopic images showed visually imperceptible differences from the real ones, achieving a mean target projection distance error of 1.55 mm. An endoleak phantom insertion experiment highlighted the effectiveness of simulating multiplanar views with real-time instrument overlays, achieving a mean needle tip error of 3.42 mm. Conclusions: Results demonstrated the efficacy of virtual fluoroscopy integrated with magnetic tracking, improving depth perception during navigation. The broad capture range of virtual fluoroscopy showed promise in improving the users understanding of X-ray imaging principles, facilitating more efficient image acquisition.

Virtual Fluoroscopy for Interventional Guidance using Magnetic Tracking

TL;DR

This work tackles depth perception and radiation exposure in fluoroscopy-guided interventions by introducing a virtual fluoroscopy workflow that integrates magnetic tracking with a radiolucent field generator. It combines automatic fluoro-CT registration, 2D-3D landmark correspondence, and a generalized C-arm pose model to render virtual views with real-time instrument overlays, enabling multiplanar visualization without excessive C-arm repositioning. Validation shows a mean 2D projection distance of about mm for simulated views and a needle-tip error around mm in phantom trials, with high frame-rate performance (e.g., ~38 fps for landmark detection and ~1.97 s per fluoro-CT registration) indicating real-time feasibility. The results suggest that MT-enabled virtual fluoroscopy can improve depth perception, reduce unnecessary fluoroscopy acquisitions, and facilitate more efficient interventional navigation, with future work focusing on broader clinical validation and workflow optimization.

Abstract

Purpose: In conventional fluoroscopy-guided interventions, the 2D projective nature of X-ray imaging limits depth perception and leads to prolonged radiation exposure. Virtual fluoroscopy, combined with spatially tracked surgical instruments, is a promising strategy to mitigate these limitations. While magnetic tracking shows unique advantages, particularly in tracking flexible instruments, it remains under-explored due to interference from ferromagnetic materials in the C-arm room. This work proposes a virtual fluoroscopy workflow by effectively integrating magnetic tracking, and demonstrates its clinical efficacy. Methods: An automatic virtual fluoroscopy workflow was developed using a radiolucent tabletop field generator prototype. Specifically, we developed a fluoro-CT registration approach with automatic 2D-3D shared landmark correspondence to establish the C-arm-patient relationship, along with a general C-arm modelling approach to calculate desired poses and generate corresponding virtual fluoroscopic images. Results: Testing on a dataset with views ranging from RAO 90 degrees to LAO 90 degrees, simulated fluoroscopic images showed visually imperceptible differences from the real ones, achieving a mean target projection distance error of 1.55 mm. An endoleak phantom insertion experiment highlighted the effectiveness of simulating multiplanar views with real-time instrument overlays, achieving a mean needle tip error of 3.42 mm. Conclusions: Results demonstrated the efficacy of virtual fluoroscopy integrated with magnetic tracking, improving depth perception during navigation. The broad capture range of virtual fluoroscopy showed promise in improving the users understanding of X-ray imaging principles, facilitating more efficient image acquisition.

Paper Structure

This paper contains 15 sections, 4 equations, 8 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Methods
  3. Hardware Integration
  4. Virtual Fluoroscopy
  5. Fluoro-CT Registration
  6. Patient Pose Initialization
  7. C-arm Pose Estimation
  8. Intensity-based Registration
  9. Evaluation Metrics
  10. Experiments and Results
  11. Landmark Correspondence and Fluoro-CT Registration
  12. Virtual Fluoroscopy
  13. Phantom Experiments
  14. Discussion
  15. Conclusion

Figures (8)

  • Figure 1: Comparison of our proposed MT-assisted guidance with the conventional one.
  • Figure 2: Comparison of the window FG with the radiolucent FG prototype, and the FG mounting frame. The top layer of the FG mounting frame comprises an acrylic plate, and the bottom layer houses the radiolucent FG prototype. Fiducials are attached to the downside of each layer.
  • Figure 3: System coordinate frames for virtual fluoroscopy.
  • Figure 4: Workflow of fluoro-CT registration.
  • Figure 5: Workflow of our 2D-3D landmark correspondence approach.
  • ...and 3 more figures