Dosimetric effect of uncorrected rotations in lung SBRT with stereotactic imaging guidance |
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| Affiliation: | 1. Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Spain;2. Servicio de Radiofísica, Hospital Universitario Virgen Macarena, Sevilla, Spain;3. Instituto de Física, Pontificia Universidad Católica de Chile, Santiago de Chile, Chile;4. Istituto Nazionale di Fisica Nucleare, Frascati, Italy;1. CELIA, Centre Laser Intenses et Applications, Université de Bordeaux-CNRS-CEA, F-33400 Talence, France;2. Department of Radiotherapy, Institut Bergonié, Comprehensive Cancer Center, F-33076 Bordeaux, France;1. German Cancer Research Center (DKFZ), Division of Medical Physics in Radiation Oncology, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany;2. National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany;3. Heidelberg University Hospital, Department of Radiation Oncology, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany;4. Advacam s.r.o., Na Balkáně 2075/70, 130 00 Praha 3, Czech Republic;5. Institute of Experimental and Applied Physics, Czech Technical University in Prague, Horská 3a/22, 12800 Prague 2, Czech Republic;1. Department of Medical Physics, Centre Oscar Lambret and University Lille 1, France;2. Academic Department of Radiation Oncology, Centre Oscar Lambret and University Lille 2, France;1. Department of Oncology and Medical Physics, Haukeland University Hospital, Bergen, Norway;2. Department of Physics and Technology, University of Bergen, Bergen, Norway;3. Department of Medical Physics, Aarhus University/Aarhus University Hospital, Aarhus, Denmark |
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| Abstract: | PurposeTo evaluate the dosimetric impact of uncorrected rotations on the planning target volume (PTV) coverage for early stage non-small cell lung cancer patients treated with stereotactic body radiotherapy using Brainlab ExacTrac image guidance.MethodsTwenty-two patients were retrospectively selected. Two scenarios of uncorrected rotations were simulated with magnitude of 1°, 2°, 3° and 5°: (1) rotation around the treatment isocenter; and (2) roll and yaw rotations around a setup isocenter. The D95 of PTV from recalculated dose on the rotated CT was compared to that from the clinical plan. A logistic regression model was used to predict the probability of dose differences between recalculated and original plans that are less than 2% based on the rotation angle, PTV volume, and distance between the treatment and setup isocenter.ResultsLogistic regression model showed the uncorrected isocentric rotations of up to 2.5° in all directions have negligible dosimetric impact. For non-isocentric rotations, a rotational error of 2° may cause significant under-dose of the PTV. Statistically significant (p < 0.05) parameters in the logistic regression model were angle for isocentric rotations, angle and distance for non-isocentric roll rotations, and angle, distance and the PTV volume for non-isocentric yaw rotations.ConclusionsThe severity of the dose deviations due to uncorrected rotations depends on the type and magnitude of the rotation, the volume of the PTV, and the distance between the treatment and setup isocenter, which should be taken into consideration when making clinical judgment of whether the rotational error could be ignored. |
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| Keywords: | Lung SBRT Rotation Dosimetry Exactrac image guidance |
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