Fiducial-based targeting accuracy for external-beam radiotherapy

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Computational Geometry

Background:

• Accurate patient positioning is critical for effective external beam radiotherapy.
• Fiducial markers are commonly used to guide radiation delivery.
• Soft tissue variability can introduce inaccuracies in fiducial-based alignment.

Purpose of the Study:

• To analyze the accuracy, robustness, and efficiency of computational methods for fiducial-based radiotherapy alignment.
• To investigate the impact of fiducial position variability on alignment accuracy.
• To compare different fiducial configurations for optimal target localization.

Main Methods:

• Analysis of three computational methods: exact closed-form solution (3 fiducials), singular value decomposition (≥4 fiducials), and iterative solution (any number of fiducials).
• Assessment of accuracy and robustness against variations in fiducial positions in soft tissue.
• Evaluation of computational efficiency for each method.

Main Results:

• All three methods, when properly implemented, provide comparable target position accuracy.
• Singular value decomposition requires modification to differentiate rotations from reflections.
• Four fiducials offer significantly improved rotation accuracy compared to three; more than five provide marginal benefits.

Conclusions:

• Fiducial-based alignment methods are generally accurate for radiotherapy.
• Careful implementation and method selection are crucial, especially for rotational accuracy.
• Optimizing the number of fiducials (four) enhances rotational precision in radiotherapy alignment.