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Reconstruction of implanted marker trajectories from cone-beam CT projection images using interdimensional
Hyekyun Chung1, Per Rugaard Poulsen2, Paul J Keall3
1Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, South Korea and Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 138-736, South Korea.
This study presents a novel method using cone-beam CT (CBCT) projection images to accurately estimate 3D tumor motion trajectories for image-guided radiotherapy. The technique enables precise real-time target tracking and retrospective analysis.
Area of Science:
- Medical physics
- Radiotherapy technology
- Image-guided interventions
Background:
- Cone-beam CT (CBCT) is crucial for image-guided radiotherapy, enabling 3D target localization.
- Gantry-mounted CBCT systems facilitate the analysis of respiratory-induced target motion using 2D projection data.
- Accurate estimation of 3D target trajectories is essential for effective radiotherapy delivery.
Purpose of the Study:
- To develop and validate a method for estimating the 3D trajectory of respiratory-induced target motion from CBCT projection images.
- To utilize interdimensional correlation modeling for predicting target motion in thoracic/abdominal regions.
- To assess the method's applicability in both retrospective and real-time image-guided radiotherapy scenarios.
Main Methods:
- Investigated interdimensional correlation of superior-inferior (SI) motion with left-right and anterior-posterior (AP) movements during gantry rotation.
- Implemented and compared simple linear and state-augmented models for interdimensional correlation analysis.
- Validated the method using 160 3D tumor trajectories from 46 patients undergoing CyberKnife treatment, simulating retrospective and on-the-fly estimation scenarios.
Main Results:
- The state-augmented model achieved a mean 3D root-mean-square error (RMSE) of 0.35 mm in retrospective simulations, outperforming the simple linear model (0.41 mm).
- For on-the-fly estimation, reliable results required over 60° of prior projections.
- Mean 3D RMSE during beam delivery was 0.42 mm (VMAT) and 0.45 mm (IMRT) using the simple linear model with 90° prior data.
Conclusions:
- The proposed interdimensional correlation method accurately estimates 3D target trajectories from CBCT projection images without external correlation models.
- The technique supports both retrospective analysis for treatment setup and real-time monitoring for respiratory gating or tracking.
- This approach enhances the precision and adaptability of image-guided radiotherapy for moving targets.
