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Proceedings Paper

Automated skull tracking for the CyberKnife image-guided radiosurgery system
Author(s): Dongshan Fu; Gopinath Kuduvalli; Vladimir Mitrovic; William Main; Larry Thomson
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Paper Abstract

We have developed an automated skull tracking method to perform near real-time patient alignment and position correction during CyberKnife image-guided intracranial radiosurgery. Digitally reconstructed radiographs (DRRs) are first generated offline from a CT study before treatment, and are used as reference images for the patient position. Two orthogonal projection X-ray images are then acquired at the time of patient alignment or treatment. Multi-phase registration is used to register the DRRs with the X-ray images. The registration in each projection is carried out independently; the results are then combined and converted to a 3-D rigid transformation. The in-plane transformation and the out-of-plane rotations are estimated using different search methods including multi-resolution matching, steepest descent minimization and one-dimensional search. Two similarity measure methods, optimized pattern intensity and sum of squared difference (SSD), are applied at different search phases to optimize both accuracy and computation speed. Experiments on an anthropomorphic skull phantom showed that the tracking accuracy (RMS error) is better than 0.3 mm for each translation and better than 0.3 degree for each rotation, and the targeting accuracy (clinically relevant accuracy) tested with the CyberKnife system is better than 1 mm. The computation time required for the tracking algorithm is within a few seconds.

Paper Details

Date Published: 12 April 2005
PDF: 12 pages
Proc. SPIE 5744, Medical Imaging 2005: Visualization, Image-Guided Procedures, and Display, (12 April 2005); doi: 10.1117/12.594984
Show Author Affiliations
Dongshan Fu, Accuray Inc. (United States)
Gopinath Kuduvalli, Accuray Inc. (United States)
Vladimir Mitrovic, Accuray Inc. (United States)
William Main, Accuray Inc. (United States)
Larry Thomson, Bristol Regional Medical Ctr. (United States)


Published in SPIE Proceedings Vol. 5744:
Medical Imaging 2005: Visualization, Image-Guided Procedures, and Display
Robert L. Galloway Jr.; Kevin R. Cleary, Editor(s)

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