Comparison of setup accuracy and intrafraction motion using stereotactic frame versus 3-point thermoplastic mask-based immobilization for fractionated cranial image guided radiation therapy |
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| Authors: | Nicola Abigail Rosenfelder Lee Corsini Helen McNair Kjell Pennert Alexandra Aitken Caroline Mary Lamb Michelle Long Enrico Clarke Mauricio Murcia Ulrike Schick Kevin Burke Sue Ashley Vincent Khoo Michael Brada |
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| Affiliation: | 1. Department of Radiation Physics, Princess Margaret Hospital, Toronto, Ontario, Canada;2. Department of Medical Physics, Tom Baker Cancer Centre, Calgary, Alberta, Canada;3. Department of Physics and Astronomy, University of Calgary, Calgary, Alberta, Canada;4. Medical Physics & Bioengineering, Canterbury District Health Board, Christchurch, New Zealand;5. MIT-Harvard Center for Ultracold Atoms, and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts;6. Department of Oncology, University of Calgary, Calgary, Alberta, Canada;1. Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland;2. Department of Radiation Oncology, University of Washington, Seattle, Washington;1. Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia;2. Centre for Biostatistics and Clinical Trials, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia;3. Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Victoria, Australia |
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| Abstract: | PurposeProspectively compare patient setup accuracy and intrafraction motion of a standard 3-point thermoplastic mask with the Gill-Thomas-Cosman relocatable stereotactic frame, during fractionated cranial radiation therapy using the ExacTrac system (Brainlab AG Feldkirchen, Germany) for daily online correction.Methods and MaterialsThe number of fractions with all postcorrection and post-treatment errors < 2 mm was assessed in 21 patients undergoing fractionated stereotactic radiation therapy (13 frame setup, 8 mask setup) using daily online correction. Achievable patient setup accuracy and total intrafraction motion were evaluated. The relative contributions of movement during floor rotation and patient movement to intrafraction motion were calculated.ResultsWith daily online correction, patient setup margins can be reduced from 1, 5, and 4 mm in the lateral, longitudinal, and vertical axes for mask setup and from 1-2, 2, and 1 mm, respectively, for frame setup to < 1 mm isotropically for either immobilization system. Intrafraction movement was small for frame setup (mean [SD], ? 0.3 [0.3], ? 1.1[0.4], and ? 0.2 [0.6] in lateral, longitudinal and vertical axes, respectively; maximum, ? 2.7 mm [longitudinal axis]), and mask-setup (mean [SD], ? 0.4 [0.5], ? 0.8 [0.7], and 0.0 [0.3], respectively; maximum, ? 2.0 mm [longitudinal axis]) and is mainly due to floor rotation. Postcorrection and post-treatment errors were all < 2 mm in 95% and 99% of fractions in the mask and frame, respectively, meeting the criteria for a 3-mm clinical target volume-planning target volume margin for either immobilization method.ConclusionsDaily online correction can compensate for less precise immobilization and permits stereotactic margins to be used for standard thermoplastic masks without the need for specialized mask systems. |
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