title: Evaluation of anatomical landmark position differences between respiration-gated MRI and four-dimensional CT for radiation therapy in patients with hepatocellular carcinoma.
abstract: OBJECTIVE
  To measure the accuracy of position differences in anatomical landmarks in gated MRI and four-dimensional CT (4D-CT) fusion planning for radiation therapy in patients with hepatocellular carcinoma (HCC).
  
  
  METHODS
  From April to December 2009, gated MR and planning 4D-CT images were obtained from 53 inoperable HCC patients accrued to this study. Gated MRI and planning 4D-CT were conducted on the same day. Manual image fusions were performed by matching the vertebral bodies. Liver volumes and three specific anatomical landmarks (portal vein conjunction, superior mesenteric artery bifurcation, and other noticeable points) were contoured from each modality. The points chosen nearest the centre of the four landmark points were compared to measure the accuracy of fusion.
  
  
  RESULTS
  The average distance differences (±standard deviation) of four validation points were 5.1 mm (±4.6 mm), 5.6 mm (±6.2 mm), 5.4 mm (±4.5 mm) and 5.1 mm (±4.8 mm). Patients who had ascites or pulmonary disease showed larger discrepancies. MRI-CT fusion discrepancy was significantly correlated with positive radiation response (p<0.05).
  
  
  CONCLUSIONS
  Approximately 5-mm anatomical landmark positional differences in all directions were found between gated MRI and 4D-CT fusion planning for HCC patients; the gap was larger in patients with ascites or pulmonary disease.
  
  
  CONCLUSIONS
  There were discrepancies of approximately 5 mm in gated MRI-CT fusion planning for HCC patients.
authors.affiliation: Department of Radiation Oncology, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: J I
authors.initials: JI
authors.lastname: Yu
authors.forename: J S
authors.initials: JS
authors.lastname: Kim
authors.forename: H C
authors.initials: HC
authors.lastname: Park
authors.forename: D H
authors.initials: DH
authors.lastname: Lim
authors.forename: Y Y
authors.initials: YY
authors.lastname: Han
authors.forename: H C
authors.initials: HC
authors.lastname: Lim
authors.forename: S W
authors.initials: SW
authors.lastname: Paik
mesh_terms: D000328:Adult; D000368:Aged; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging* / Q000473:pathology*; D006528:Carcinoma, Hepatocellular / Q000175:diagnosis* / Q000532:radiotherapy*; D005260:Female; D056973:Four-Dimensional Computed Tomography; D006801:Humans; D008113:Liver Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D061089:Radiotherapy, Image-Guided; D015203:Reproducibility of Results; D055425:Respiratory-Gated Imaging Techniques; D012680:Sensitivity and Specificity; D016896:Treatment Outcome