Translational and rotational localization errors in cone-beam CT based image-guided lung stereotactic radiotherapy |
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| Institution: | 1. Unit of Radiation Research, European Institute of Oncology, Milano, Italy;2. Department of Radiation Oncology, European Institute of Oncology, Milano, Italy;3. Unit of Medical Physics, European Institute of Oncology, Milano, Italy;4. Department of Health Sciences, Università degli Studi di Milano, Milano, Italy;5. Scientific Director, European Institute of Oncology, Milano, Italy;2. The University of Manchester, Manchester Academic Health Science Centre, Institute of Cancer Sciences, Manchester, UK;3. Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, UK;1. Department of Radiation Oncology, Washington University School of Medicine, Saint Louis, MO, USA;2. Department of Radiation Oncology, University of Colorado School of Medicine, Colorado Springs, CO, USA;3. Department of Radiation Oncology, Mayo Clinic, Rochester, MN, USA;4. Missouri Baptist Medical Center, St. Louis, MO, USA;1. Department of Medical Physics, Tom Baker Cancer Centre, 1331 29 Street NW, Calgary, AB T2N 4N2, Canada;2. Department of Physics & Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada;3. Department of Oncology, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada |
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| Abstract: | PurposeAccurate localization is crucial in delivering safe and effective stereotactic body radiation therapy (SBRT). The aim of this study was to analyse the accuracy of image-guidance using the cone-beam computed tomography (CBCT) of the VERO system in 57 patients treated for lung SBRT and to calculate the treatment margins.Materials and methodsThe internal target volume (ITV) was obtained by contouring the tumor on maximum and mean intensity projection CT images reconstructed from a respiration correlated 4D-CT. Translational and rotational tumor localization errors were identified by comparing the manual registration of the ITV to the motion-blurred tumor on the CBCT and they were corrected by means of the robotic couch and the ring rotation. A verification CBCT was acquired after correction in order to evaluate residual errors.ResultsThe mean 3D vector at initial set-up was 6.6 ± 2.3 mm, which was significantly reduced to 1.6 ± 0.8 mm after 6D automatic correction. 94% of the rotational errors were within 3°. The PTV margins used to compensate for residual tumor localization errors were 3.1, 3.5 and 3.3 mm in the LR, SI and AP directions, respectively.ConclusionsOn-line image guidance with the ITV–CBCT matching technique and automatic 6D correction of the VERO system allowed a very accurate tumor localization in lung SBRT. |
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| Keywords: | Translational and rotational localization error Lung SBRT Image-guided radiotherapy |
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