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Three-Dimensional Dose/MU Verification Tool for Cyberknife Radiotherapy Plans

P Dvorak

P Dvorak*, The London Clinic, London, UK

SU-E-T-34 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall

Purpose: To improve independent dose/MU verification for Cyberknife treatment plans based on three-dimensional dose calculation including DVH and isodose display and DVH statistics.

Methods: Independent voxel-based dose calculation application was developed on MATLAB platform based on DICOM CT images, DICOM RT structures, DICOM RT dose and Cyberknife treatment plan XML file imported from Cyberknife dedicated TPS (Multiplan) for a given case. Dose calculation algorithm reproduces standard RayTracing algorithm used in MultiPlan including body surface consideration and water-equivalent depth density scaling. To speed up performance only voxels of preselected volume structures are calculated. In addition, voxels forming three major planes through normalization/reference point are calculated for isodose comparison on background of corresponding CT images and selected volume structures.

Results: The application displays three integral DVHs per preselected structure: original from DICOM dose file, recalculated based on original DICOM dose and DICOM structures, and calculated based on independent dose and DICOM structures. DVH statistics table shows statistically robust Dmin, Dmax and Dmean and their percentage deviations for all three modalities above. In addition, percentage dose difference histograms are displayed for every preselected structure.

Conclusions: Independent plan dose/MU check is recommended or even mandatory in some countries. Conventional Cyberknife dose/MU check procedure is based on a beam dose/MU list export from Multiplan with individual beam contributions to a single reference point. This approach can not handle well plans with multiple-lesions and/or non-isocentric beam geometries in general due to frequent dose-outside a field situations. Newly developed application is voxel-based and handles well multiple-lesion cases. Unlike conventional approach, it is also more independent as it verifies parameters such as depth, equivalent depth and off-axis distance i.e. key parameters for dose/MU calculation. As a 3D tool it also presents results in clinically relevant patient-specific metrics.

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