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Fig. 1 | Radiation Oncology

Fig. 1

From: Per-fraction positional and dosimetric performance of prone breast tangential radiotherapy on Halcyon™ linear accelerator assessed with daily rapid kilo-voltage cone beam computed tomography: a single-institution pilot study

Fig. 1

Illustration of daily synthetic CT generation and Breast PTV Eval contouring methods, as well as visual representation of variables used in predictive modeling. a Planning CT for 8 patients were deformed to each of 16 daily CBCTs taken by Halcyon v2.0. A total of 126 deformed CTs were generated. The daily shift from matching CBCT-CT was applied to copied plan isocenter to correct for daily couch shifts. b Generated Daily Breast PTV Eval mimicked the original contour as closely as possible, including a 5 mm subtraction from the skin surface. c Some predictive variables used in this paper are defined here. SSD-derived breast width diameter (BWD) is calculated from source-to-surface distances (SSD) of lateral and medial beams, giving an estimate of patient’s breast diameter as well as any set-up errors resulting in distorted SSDs. Residual shift vector was derived from comparing centers of mass of planned breast PTV eval volume to that of daily volume, adjusted for couch shift. Dice similarity coefficient (DSC) was calculated from this same setup using the intersection and union of PTV volumes

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Radiation Oncology

ISSN: 1748-717X

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