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Updated: Mar 21, 2026
Dynamic Lung Tumor Tracking for Stereotactic Ablative Body Radiation Therapy
Published on: June 7, 2015
Quantifying upright positioning accuracy with optical surface tracking in radiotherapy
Yusuke Nomura1, Sodai Tanaka1, Hideyuki Takei1
1Department of Accelerator and Medical Physics, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Chiba, Japan.
Purpose:
This study quantified inter- and intra-fractional setup accuracies in the upright posture and compared them among setups with different immobilization methods.
Methods:
Two and four setups were examined for abdominal and head and neck (HN) cancer treatments, respectively. Fifteen asymptomatic volunteers were positioned to a replicated chair of an upright radiotherapy platform with leg immobilization devices, backrest attachments, thermoplastic masks, and vacuum cushions. The 3D positions of the subject body and masks were monitored by calculating 3D point clouds of 26 surface markers from three camera images. The inter-fractional setup errors were calculated by repeating the same setup five times. The intra-fractional displacements were evaluated while the subjects remained in the setups for 20 min. These setup errors and displacements were compared among the setups with different immobilization methods. The intra-fractional displacements were also compared between this study and previous studies in the supine posture.
Results:
Inter-fractional setup errors in the abdominal setups were reduced from 6.6 ± 3.3 to 3.9 ± 1.7 mm by using the masks. The HN setup using both the leg immobilization devices and backrest attachments had the setup errors of 2.9 ± 1.7 mm. This was smaller than the setup errors observed in three other HN setups that did not use either or both of the devices together. Intra-fractional displacements of these abdominal and HN setups with the immobilization devices were 1.9 ± 1.1 and 1.8 ± 1.5 mm, respectively, which were smaller than those in the other setups. These displacements were equivalent to those in the previous studies.
Conclusions:
Utilizing the masks increased upright setup accuracy in the abdominal setup. The leg immobilization devices and backrest attachments provided the highest setup accuracy in the upright HN setup. These findings will be useful to expand the applicability of upright radiotherapy for various cancer treatments.
