Dosimetric impact of hysteresis on lung cancer tomotherapy: A moving phantom study |
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| Affiliation: | 1. Institut Jules Bordet – Université Libre de Bruxelles (ULB), Department of Radiation Oncology, Brussels, Belgium;2. Department of Radiation Oncology, BC Cancer Agency – Abbotsford Center, Canada;3. Department of Radiation Oncology, BC Cancer Agency – Vancouver Center, Canada;1. Physics Service of Radiation Oncology Dept., Humanitas Clinical and Research Hospital, Milan-Rozzano, Italy;2. Radiotherapy and Radiosurgery department, Humanitas Clinical and Research Hospital, Milan-Rozzano, Italy;3. Department of Biomedical Sciences, Humanitas University, Rozzano, Milano, Italy;1. Department of Radiological Sciences, Faculty of Health Sciences, Komazawa University, Tokyo, Japan;2. Department of Radiology, The University of Tokyo Hospital, Tokyo, Japan;3. Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota;4. Department of Radiation Oncology, Osaka University, Osaka, Japan;5. Department of Radiation Oncology and Beckman Research Institute, City of Hope, Duarte, California;1. Department of Oncology, Aarhus University Hospital, Denmark;2. Institute of Clinical Medicine, Aarhus University, Denmark;3. Department of Medical Physics, Aarhus University Hospital, Denmark;1. Pôle de Pneumologie, ORL & Dermatologie (PNEU), Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium;2. Haute Ecole Léonard de Vinci, PARNASSE-ISEI, Brussels, Belgium;3. Secteur de kinésithérapie, Cliniques universitaires Saint-Luc, Brussels, Belgium;4. Service de Pneumologie, Cliniques universitaires Saint-Luc, Brussels, Belgium;5. Molecular Imaging, Radiotherapy and Oncology (MIRO), Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium;6. Department of Radiation Oncology, Cliniques universitaires Saint Luc, Brussels, Belgium |
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| Abstract: | PurposeTo investigate the dosimetric impact of hysteresis on lung cancer tomotherapy.MethodsMeasurements were acquired using MapCheck with an XY4D motion simulation table. Six hysteresis states (0, π/32, π/16, π/8, 3π/16, and π/4) were considered with sinusoidal motions in the superior–inferior and left–right orientations. The measured data were analyzed both globally (from all detectors) and structure-by-structure in the measurement plane. The dose difference (DD) analysis method with local normalization in the absolute dose mode with a DD threshold of 6 cGy was adopted to analyze each hysteresis vs. static state (H(1)S) and nonzero vs. zero hysteresis (H(1)0). The threshold was 10% for all analyses. Wilcoxon signed rank tests with significance level p = 0.05 were used for statistical analysis.ResultsThe DD analysis of each H(1)S mostly indicated that the passing rate differed between structures but was similar between hysteresis states. The DD analysis of H(1)0 showed that the passing rate decreased with increasing hysteresis. The differences between larger hysteresis (≥3π/16) and other states were significant for comparisons between global, left lung, chest wall, and target. Both analyses showed that the DD distribution changed with hysteresis.ConclusionsHysteresis difference causes the DD distribution to change. Structural difference had more impact than hysteresis state difference on hysteresis motion vs. static comparisons. Remarkable effects on nonzero vs. zero hysteresis comparisons were only seen for structures closely related to the target at large hysteresis. Small organs at risk that are close to the target need to be considered further. |
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| Keywords: | Dosimetric impact Hysteresis Lung cancer Tomotherapy |
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