Tumor motion changes in stereotactic body radiotherapy for liver tumors: an evaluation based on four-dimensional cone-beam computed tomography and fiducial markers.
BACKGROUND
For stereotactic body radiation therapy (SBRT) of liver tumors, tumor motion induced by respiration must be taken into account in planning and treatment. We evaluated whether liver tumor motion at the planning simulation represents liver tumor motion during SBRT, and estimated inter- and intrafractional tumor motion changes in patients undergoing liver SBRT.


METHODS
Ten patients underwent four-dimensional cone-beam computed tomography (4D-CBCT) image-guided liver SBRT with abdominal compression (AC) and fiducial markers. 4D-CBCT was performed to evaluate liver tumor motion at the planning simulation, pre-, and post-SBRT. The translational distances at the center position of the fiducial markers from all 10 phases on the 4D-CBCT images were measured as the extent of the liver tumor motion in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions. Pearson correlation coefficients were calculated to evaluate the correlation between liver tumor motion of the planning simulation and the mean liver tumor motion of the pre-SBRT. Inter- and intrafractional liver tumor motion changes were measured based on the 4D-CBCT of planning simulation, pre-, and post-SBRT. Significant inter- and intrafractional changes in liver tumor motion were defined as a change of >3 mm.


RESULTS
The mean (± SD) liver tumor motion of the planning simulation 4D-CBCT was 1.7 ± 0.8 mm, 2.4 ± 2.2 mm, and 5.3 ± 3.3 mm, in the LR, AP, and SI directions, respectively. Those of the pre-SBRT 4D-CBCT were 1.2 ± 0.7 mm, 2.3 ± 2.3 mm, and 4.5 ± 3.8 mm, in the LR, AP, and SI directions, respectively. There was a strong significant correlation between liver tumor motion of the planning simulation and pre-SBRT in the LR (R = 0.7, P < 0.01), AP (R = 0.9, P < 0.01), and SI (R = 0.9, P < 0.01) directions. Significant inter- and intrafractional liver tumor motion changes occurred in 10 and 2% of treatment fractions, respectively.


CONCLUSIONS
Liver tumor motion at the planning simulation represents liver tumor motion during SBRT. Inter- and intrafractional liver tumor motion changes were small in patients with AC.
Department of Radiological Technology, Kumamoto University Hospital, 1-1-1 Honjo, Chuo-ku, Kumamoto, 860-8556, Japan. shimo@room.ocn.ne.jp.|Graduate School of Health Sciences, Kumamoto University, 4-24-1 Kuhonji, Chuo-ku, Kumamoto, 862-0976, Japan. shimo@room.ocn.ne.jp.
Yoshinobu
Y
Shimohigashi
Department of Radiation Oncology, Kumamoto University Hospital, Kumamoto, Japan.
Ryo
R
Toya
Department of Radiation Oncology, Kumamoto University Hospital, Kumamoto, Japan.
Tetsuo
T
Saito
Department of Diagnostic Radiology, Kumamoto University Hospital, Kumamoto, Japan.
Osamu
O
Ikeda
Department of Radiological Technology, Kumamoto University Hospital, 1-1-1 Honjo, Chuo-ku, Kumamoto, 860-8556, Japan.
Masato
M
Maruyama
Department of Radiological Technology, Kumamoto University Hospital, 1-1-1 Honjo, Chuo-ku, Kumamoto, 860-8556, Japan.
Keisuke
K
Yonemura
Department of Radiological Technology, Kumamoto University Hospital, 1-1-1 Honjo, Chuo-ku, Kumamoto, 860-8556, Japan.
Yuji
Y
Nakaguchi
Department of Radiological Technology, Kumamoto University Hospital, 1-1-1 Honjo, Chuo-ku, Kumamoto, 860-8556, Japan.
Yudai
Y
Kai
Department of Diagnostic Radiology, Kumamoto University Hospital, Kumamoto, Japan.
Yasuyuki
Y
Yamashita
Department of Radiation Oncology, Kumamoto University Hospital, Kumamoto, Japan.
Natsuo
N
Oya
Department of Health Sciences, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
Fujio
F
Araki
D016477:Artifacts; D005260:Female; D057918:Fiducial Markers; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D008297:Male; D009038:Motion; D009068:Movement; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D012119:Respiration; D012189:Retrospective Studies
Four-dimensional cone-beam computed tomography; Image-guided radiotherapy; Internal target volume; Liver tumor; Stereotactic body radiotherapy