Setup uncertainties and appropriate setup margins in the head-tilted supine position of whole-brain radiotherapy (WBRT)

• Published in: PloS one Vol. 17; no. 8; p. e0271077
• Main Authors: Park, Jae Won, Yea, Ji Woon, Park, Jaehyeon, Oh, Se An
• Format: Journal Article
• Language: English
• Published: San Francisco Public Library of Science 04.08.2022; Public Library of Science (PLoS)
• Subjects: Biology and Life Sciences; Brain; Brain cancer; Brain tumors; Care and treatment; Complications and side effects; Computed tomography; CT imaging; Engineering and Technology; Evaluation; Exocrine glands; Head; Medical equipment; Medicine and Health Sciences; Normal distribution; Patient outcomes; Patients; Physical Sciences; Planning; Radiation therapy; Radiotherapy; Random errors; Registration; Research and Analysis Methods; Review boards; Supine position; Systematic errors; Translation; Tumors; Uncertainty; Yaw; South Korea; United States > US; Germany
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0271077

Various applications of head-tilting techniques in whole-brain radiotherapy (WBRT) have been introduced. However, a study on the setup uncertainties and margins in head-tilting techniques has not been reported. This study evaluated the setup uncertainties and determined the appropriate planning target volume (PTV) margins for patients treated in the head-tilted supine (ht-SP) and conventional supine position (c-SP) in WBRT. Thirty patients who received WBRT at our institution between October 2020 and May 2021 in the c-SP and ht-SP were investigated. The DUON head mask (60124, Orfit Industries, Wijnegem, Belgium) was used in the c-SP, and a thermoplastic U-Frame Mask (R420U, Klarity Medical & Equipment Co. Ltd., Lan Yu, China) was used in the ht-SP. Daily setup verification using planning computed tomography (CT) and cone-beam CT was corrected for translational (lateral, longitudinal, and vertical) and rotational (yaw) errors. In the c-SP, the means of systematic errors were -0.80, 0.79, and 0.37 mm and random errors were 0.27, 0.54, and 0.39 mm in the lateral, longitudinal, and vertical translational dimensions, respectively. Whereas, for the ht-SP, the means of systematic errors were -0.07, 0.73, and -0.63 mm, and random errors were 0.75, 1.39, 1.02 mm in the lateral, longitudinal, and vertical translational dimensions, respectively. The PTV margins were calculated using Stroom et al.’s [2Σ+0.7σ] and van Herk et al.’s recipe [2.5Σ+0.7σ]. Appropriate PTV margins with van Herk et al.’s recipe in WBRT were <2 mm and 1.5° in the c-SP and <3 mm and 2° in the ht-SP in the translational and rotational directions, respectively. Although the head tilt in the supine position requires more margin, it can be applied as a sufficiently stable and effective position in radiotherapy.