Abstract
In this study, we analyzed fiducial position data of three lung, two liver and one pancreas patients treated by CyberKnife SBRT in order to assess the deformation of moving tumors. Each patient had 4 fiducials implanted in or near the tumor as the surrogates for tracking the tumor. The fiducial positions in 3D were determined based on a pair of orthogonal x-ray images. The centroids of each fiducial in the image pair were first digitized manually and paired. The 3D coordinates of the fiducial was then derived using the geometry of CyberKnife imaging system for real-time tumor tracking. For each patient, about 20 pairs of images were analyzed in time sequence. The sum of the inter-fiducial distances was calculated as a parameter for a surrogate tumor volume, and the tumor volume is assumed proportional to the cube of the sum of the distance based on scaling laws.
Variations of the calculated surrogate tumor volume were observed for all 6 patients. For one lung tumor in the lower lobe near the chest wall, the tumor volume increased and peaked at the 4th image (2.7%) and decreased to the minimum at the end of treatment (-4.7%). For the other two lung tumors, tumor volumes varied from -4.5 to 3.4% and -4.5 to 1.1%. Relatively smaller volume variations were observed in the two liver tumors (from -1.6 to 2.8% and -3.6 to 3.2%). In the pancreas case, the variation was from -1.8 to 4.1%. Tumor volume variations demonstrated quite different behaviors among different tumor locations and disease sites. In all 3 lung tumors, the volumes tended to decrease near the end of the treatment due to radiation response.
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© 2013 Springer-Verlag Berlin Heidelberg
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Xu, Q., LaCouture, T., Che, Y. (2013). Stereo Imaging of Internal Fiducials Indicates Intrafractional Tumor Deformation during CyberKnife SBRT. In: Long, M. (eds) World Congress on Medical Physics and Biomedical Engineering May 26-31, 2012, Beijing, China. IFMBE Proceedings, vol 39. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-29305-4_508
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DOI: https://doi.org/10.1007/978-3-642-29305-4_508
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-642-29304-7
Online ISBN: 978-3-642-29305-4
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