title: Evaluation of the motion of lung tumors during stereotactic body radiation therapy (SBRT) with four-dimensional computed tomography (4DCT) using real-time tumor-tracking radiotherapy system (RTRT).
abstract: OBJECTIVE
  We investigated the usefulness of four-dimensional computed tomography (4DCT) performed before stereotactic body radiation therapy (SBRT) in determining the internal margins for peripheral lung tumors.
  
  
  METHODS
  The amplitude of the movement of a fiducial marker near a lung tumor measured using the maximum intensity projection (MIP) method in 4DCT imaging was acquired before the SBRT (AmpCT) and compared with the mean amplitude of the marker movement during SBRT (Ampmean) and with the maximum amplitude of the marker movement during SBRT (Ampmax) using a real-time tumor-tracking radiotherapy (RTRT) system with 22 patients.
  
  
  RESULTS
  There were no significant differences between the means of the Ampmean and the means of the AmpCT in all directions (LR, P = 0.45; CC, P = 0.80; AP, P = 0.65). The means of the Ampmax were significantly larger than the means of the AmpCT in all directions (LR, P < 0.01; CC, P = 0.03; AP, P < 0.01). In the lower lobe, the mean difference of the AmpCT from the mean of the Ampmax was 5.7 ± 8.0 mm, 12.5 ± 16.7 mm, and 6.8 ± 8.5 mm in the LR, CC, and AP directions, respectively.
  
  
  CONCLUSIONS
  Acquiring 4DCT MIP images before the SBRT treatment is useful to establish the mean amplitude for a patient during SBRT but it underestimates the maximum amplitude during actual SBRT. Caution must be paid to determine the margin with the 4DCT especially for tumors at the lower lobe where it is of the potentially greatest benefit.
authors.affiliation: Department of Radiation Medicine, Hokkaido University Graduate School of Medicine, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Harada
authors.affiliation: Department of Radiation Oncology, Hokkaido University Hospital, North-14 West-5, Kita-ku, Sapporo 060-8638, Japan; Global Station for Medical Science and Engineering, Global Institution for Collaborative Research and Education, Hokkaido University Graduate School of Medicine, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan. Electronic address: noriwokatoh@med.hokudai.ac.jp.
authors.forename: Norio
authors.initials: N
authors.lastname: Katoh
authors.affiliation: Department of Radiation Oncology, Hokkaido University Hospital, North-14 West-5, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Suzuki
authors.affiliation: Department of Biostatistics, Hokkaido University Graduate School of Medicine, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Yoichi M
authors.initials: YM
authors.lastname: Ito
authors.affiliation: Global Station for Medical Science and Engineering, Global Institution for Collaborative Research and Education, Hokkaido University Graduate School of Medicine, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan; Department of Radiation Oncology, Hokkaido University Graduate School of Medicine, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Shimizu
authors.affiliation: Department of Radiation Medicine, Hokkaido University Graduate School of Medicine, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Rikiya
authors.initials: R
authors.lastname: Onimaru
authors.affiliation: Department of Radiation Oncology, Hokkaido University Hospital, North-14 West-5, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Inoue
authors.affiliation: Department of Radiation Oncology, Hokkaido University Hospital, North-14 West-5, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Miyamoto
authors.affiliation: Department of Radiation Medicine, Hokkaido University Graduate School of Medicine, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan; Global Station for Medical Science and Engineering, Global Institution for Collaborative Research and Education, Hokkaido University Graduate School of Medicine, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shirato
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D057918:Fiducial Markers; D056973:Four-Dimensional Computed Tomography; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000532:radiotherapy*; D008875:Middle Aged; D009068:Movement; D016634:Radiosurgery; D012119:Respiration; D013997:Time Factors
keywords: Four-dimensional computed tomography; Organ motion; Real-time tumor-tracking radiotherapy; Stereotactic body radiation therapy