title: Analysis of the Setup Uncertainty and Margin of the Daily ExacTrac 6D Image Guide System for Patients with Brain Tumors.
abstract: This study evaluated the setup uncertainties for brain sites when using BrainLAB's ExacTrac X-ray 6D system for daily pretreatment to determine the optimal planning target volume (PTV) margin. Between August 2012 and April 2015, 28 patients with brain tumors were treated by daily image-guided radiotherapy using the BrainLAB ExacTrac 6D image guidance system of the Novalis-Tx linear accelerator. DUONTM (Orfit Industries, Wijnegem, Belgium) masks were used to fix the head. The radiotherapy was fractionated into 27-33 treatments. In total, 844 image verifications were performed for 28 patients and used for the analysis. The setup corrections along with the systematic and random errors were analyzed for six degrees of freedom in the translational (lateral, longitudinal, and vertical) and rotational (pitch, roll, and yaw) dimensions. Optimal PTV margins were calculated based on van Herk et al.'s [margin recipe = 2.5∑ + 0.7σ - 3 mm] and Stroom et al.'s [margin recipe = 2∑ + 0.7σ] formulas. The systematic errors (∑) were 0.72, 1.57, and 0.97 mm in the lateral, longitudinal, and vertical translational dimensions, respectively, and 0.72°, 0.87°, and 0.83° in the pitch, roll, and yaw rotational dimensions, respectively. The random errors (σ) were 0.31, 0.46, and 0.54 mm in the lateral, longitudinal, and vertical rotational dimensions, respectively, and 0.28°, 0.24°, and 0.31° in the pitch, roll, and yaw rotational dimensions, respectively. According to van Herk et al.'s and Stroom et al.'s recipes, the recommended lateral PTV margins were 0.97 and 1.66 mm, respectively; the longitudinal margins were 1.26 and 3.47 mm, respectively; and the vertical margins were 0.21 and 2.31 mm, respectively. Therefore, daily setup verifications using the BrainLAB ExacTrac 6D image guide system are very useful for evaluating the setup uncertainties and determining the setup margin.
authors.affiliation: Department of Radiation Oncology, Yeungnam University Medical Center, Daegu, Korea.
authors.forename: Se An
authors.initials: SA
authors.lastname: Oh
authors.affiliation: Department of Radiation Oncology, Yeungnam University Medical Center, Daegu, Korea.|Department of Radiation Oncology, Yeungnam University College of Medicine, Daegu, Korea.
authors.forename: Ji Woon
authors.initials: JW
authors.lastname: Yea
authors.affiliation: Department of Radiation Oncology, Kyungpook National University School of Medicine, Daegu, Korea.
authors.forename: Min Kyu
authors.initials: MK
authors.lastname: Kang
authors.affiliation: Department of Radiation Oncology, Yeungnam University Medical Center, Daegu, Korea.
authors.forename: Jae Won
authors.initials: JW
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, Yeungnam University Medical Center, Daegu, Korea.|Department of Radiation Oncology, Yeungnam University College of Medicine, Daegu, Korea.
authors.forename: Sung Kyu
authors.initials: SK
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001932:Brain Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D054893:Cone-Beam Computed Tomography; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D018365:Neoplasm, Residual / Q000175:diagnosis; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D016896:Treatment Outcome; D035501:Uncertainty