title: Is diaphragm motion a good surrogate for liver tumor motion?
abstract: OBJECTIVE
  To evaluate the relationship between liver tumor motion and diaphragm motion.
  
  
  METHODS
  Fourteen patients with hepatocellular carcinoma (10 of 14) or liver metastases (4 of 14) undergoing radiation therapy were included in this study. All patients underwent single-slice cine-magnetic resonance imaging simulations across the center of the tumor in 3 orthogonal planes. Tumor and diaphragm motion trajectories in the superior-inferior (SI), anterior-posterior (AP), and medial-lateral (ML) directions were obtained using an in-house-developed normalized cross-correlation-based tracking technique. Agreement between the tumor and diaphragm motion was assessed by calculating phase difference percentage, intraclass correlation coefficient, and Bland-Altman analysis (Diff). The distance between the tumor and tracked diaphragm area was analyzed to understand its impact on the correlation between the 2 motions.
  
  
  RESULTS
  Of all patients, the mean (±standard deviation) phase difference percentage values were 7.1% ± 1.1%, 4.5% ± 0.5%, and 17.5% ± 4.5% in the SI, AP, and ML directions, respectively. The mean intraclass correlation coefficient values were 0.98 ± 0.02, 0.97 ± 0.02, and 0.08 ± 0.06 in the SI, AP, and ML directions, respectively. The mean Diff values were 2.8 ± 1.4 mm, 2.4 ± 1.1 mm, and 2.2 ± 0.5 mm in the SI, AP, and ML directions, respectively. Tumor and diaphragm motions had high concordance when the distance between the tumor and tracked diaphragm area was small.
  
  
  CONCLUSIONS
  This study showed that liver tumor motion had good correlation with diaphragm motion in the SI and AP directions, indicating diaphragm motion in the SI and AP directions could potentially be used as a reliable surrogate for liver tumor motion.
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina; School of Information Science and Engineering, Shandong University, Jinan, Shandong, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Yang
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Jing
authors.initials: J
authors.lastname: Cai
authors.affiliation: School of Information Science and Engineering, Shandong University, Jinan, Shandong, China.
authors.forename: Hongjun
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Chang
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Brian G
authors.initials: BG
authors.lastname: Czito
authors.affiliation: Department of Radiology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Mustafa R
authors.initials: MR
authors.lastname: Bashir
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Manisha
authors.initials: M
authors.lastname: Palta
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina. Electronic address: fangfang.yin@duke.edu.
authors.forename: Fang-Fang
authors.initials: FF
authors.lastname: Yin
mesh_terms: D000328:Adult; D000368:Aged; D006528:Carcinoma, Hepatocellular / Q000532:radiotherapy*; D003964:Diaphragm / Q000502:physiology*; D005260:Female; D006801:Humans; D008099:Liver / Q000502:physiology*; D008113:Liver Neoplasms / Q000532:radiotherapy* / Q000556:secondary; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D012119:Respiration; D055815:Young Adult