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Potential position errors using fiducial markers for gated image guided radiotherapy
Martin S Nielsen1, M W Nyström, Jesper Carl
1Department of Medical Physics, Aalborg University Hospital , Denmark.
Acta Oncologica (Stockholm, Sweden)
|August 30, 2013
Summary
Fiducial motion during radiotherapy planning can cause position errors. This study found that fiducial type, orientation, and speed impact accuracy in four-dimensional CT (4DCT) and image-guided radiotherapy (IGRT).
Area of Science:
- Medical Physics
- Radiotherapy Technology
- Image Guided Therapy
Background:
- Fiducials serve as surrogates for target positioning in radiotherapy.
- Fiducial motion can introduce position errors in four-dimensional CT (4DCT) and image-guided radiotherapy (IGRT).
Purpose of the Study:
- To evaluate fiducial detection accuracy in 4DCT and gated IGRT.
- To assess the impact of fiducial type, size, and orientation on position errors.
Main Methods:
- Inserted a gold marker (GM) and nickel-titanium (NiTi) stents (5, 10, 15 mm) into a moving phantom.
- Measured fiducial position errors in 4DCT and BrainLAB's gated IGRT by comparing detected to actual positions.
Main Results:
- Fiducial position errors in 4DCT correlated with speed, type, and orientation.
- Smaller NiTi stents (5 mm) and 45° orientation showed lower detection accuracy.
- 4DCT errors reached up to 4.0 mm; gated IGRT errors were up to 1.9 mm with no speed correlation.
Conclusions:
- Clinical radiotherapy planning using fiducials for moving targets requires margins up to 5.5 mm.
- Potential systematic position errors necessitate careful consideration during treatment planning.
