title: The accuracy of extracted target motion trajectories in four-dimensional cone-beam computed tomography for lung cancer patients.
abstract: To quantify the accuracy of extracted target motion trajectories in dual-source four-dimensional cone-beam computed tomography (4D-CBCT) by comparison with the actual three-dimensional (3D) target motion acquired simultaneously during 4D-CBCT scan.
  
  
  
  4D-CBCT scans were performed for 19 different sinusoidal-like patterns and 13 lung cancer patients with implanted markers. Internal (In) or external (Ex) surrogates with amplitude (Amp)- or phase (Ph)-based sorting were used for the reconstructions. The targets were a pseudo-tumor and implanted marker for the phantom and clinical studies, respectively. The accuracy was evaluated by determining the maximum error (MaxEi) between the 3D target position extracted from 4D-CBCT and the actual 3D target position detected by fluoroscopy in each ith phase (0⩽i⩽7).
  
  
  
  Median peak-to-peak target displacements in the superior-inferior (SI) direction were 20.6 and 20.6mm in the phantom and clinical studies, respectively. In the phantom and clinical studies, the maximum of median MaxEis in the SI direction was 4.6 and 9.2mm in the In_Ph reconstruction. In the clinical study, the maximum of median MaxEis was observed during the end-inhalation phase among all reconstruction approaches.
  
  
  
  This study showed the magnitude of underestimation toward the inferior direction of target motion in clinical 4D-CBCT.
authors.affiliation: Department of Nuclear Engineering, Graduate School of Engineering, Kyoto University, Japan; Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors.forename: Hiraku
authors.initials: H
authors.lastname: Iramina
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan. Electronic address: m_nkmr@kuhp.kyoto-u.ac.jp.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Iizuka
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors.forename: Takamasa
authors.initials: T
authors.lastname: Mitsuyoshi
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Matsuo
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Mizowaki
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hiraoka
authors.affiliation: Department of Nuclear Engineering, Graduate School of Engineering, Kyoto University, Japan.
authors.forename: Ikuo
authors.initials: I
authors.lastname: Kanno
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D005260:Female; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D009038:Motion; D019047:Phantoms, Imaging; D015203:Reproducibility of Results
keywords: 4D-CBCT; Respiratory signal; Sorting method; Target motion trajectory