title: Analysis of intrafractional organ motion by megavoltage computed tomography in patients with lung cancer treated with image-guided stereotactic body radiotherapy using helical tomotherapy.
abstract: OBJECTIVE
  To analyze intrafractional organ motion in patients with lung cancer treated with image-guided stereotactic body radiotherapy using helical tomotherapy (SBRT-HT).
  
  
  METHODS
  Data from 25 patients with lung cancer who received 50 Gy/5 fractions of SBRT-HT were analyzed. Slow-scan megavoltage computed tomography (MVCT) images were acquired before (pre-MVCT) and after (post-MVCT) each fraction. We analyzed the imaging quality of the 124 post-MVCT images to identify tumor contours using low-density settings. Next we examined tumor contour deviations from the planning target volume (PTV) in post-MVCT images for intrafractional tumor displacement.
  
  
  RESULTS
  Image quality was determined as good in 111/124 images from 22 patients (92%). None of the upper lung tumor images were of poor quality (74 images in 15 patients), whereas lower lung tumors yielded 14 poor-quality images out of the 50 images (3/10 patients). The difference in image quality between upper and lower lung tumors was statistically significant (p<0.01), especially when accompanied by interstitial lung shadows. Deviations in tumor position in post-MVCT images were analyzed in 110 images from 23 patients and revealed 99 images (90%) with tumor contours confined to PTV. In upper lung tumors, 4/74 images in 15 patients (5.4%) showed tumor contour deviations outside PTV. Lower lung tumors showed a higher rate of deviation with 7/36 images in 8 patients (19.4%) showing tumor contour deviations outside PTV (p<0.05). The maximum deviation was 1 mm for upper lung tumors and 2 mm for lower lung tumors.
  
  
  CONCLUSIONS
  Upper lung tumors are good candidates for MVCT image-guided SBRT-HT. However, lower lung tumors, especially those adjacent to the diaphragm or pleura, can be difficult to assess, warranting precise dose delivery by MVCT image-guided SBRT-HT.
authors.affiliation: Department of Radiology, Ujitakeda Hospital, Uji-city, Kyoto, Japan Department of Radiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto, Japan.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Aibe
authors.affiliation: Department of Radiology, Ujitakeda Hospital, Uji-city, Kyoto, Japan Department of Radiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto, Japan hideya10@hotmail.com.
authors.forename: Hideya
authors.initials: H
authors.lastname: Yamazaki
authors.affiliation: Department of Radiology, Ujitakeda Hospital, Uji-city, Kyoto, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Nishimura
authors.affiliation: Department of Radiology, Ujitakeda Hospital, Uji-city, Kyoto, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Oota
authors.affiliation: Department of Radiology, Ujitakeda Hospital, Uji-city, Kyoto, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Iwama
authors.affiliation: Department of Radiology, Ujitakeda Hospital, Uji-city, Kyoto, Japan Department of Radiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto, Japan.
authors.forename: Satoaki
authors.initials: S
authors.lastname: Nakamura
authors.affiliation: Department of Radiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto, Japan.
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Ikeno
authors.affiliation: Department of Radiology, Osaka Medical College, Takatsuki City, Osaka, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Yoshida
authors.affiliation: Department of Radiology, Ujitakeda Hospital, Uji-city, Kyoto, Japan.
authors.forename: Haruumi
authors.initials: H
authors.lastname: Okabe
authors.affiliation: Department of Radiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Yamada
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D036542:Tomography, Spiral Computed / Q000379:methods*
keywords: Tomotherapy; image-guided SBRT; lung cancer; soft tissue matching