title: Reconstruction of the treatment area by use of sinogram in helical tomotherapy.
abstract: BACKGROUND
  TomoTherapy (Accuray, USA) has an image-guided radiotherapy system with a megavoltage (MV) X-ray source and an on-board imaging device. This system allows one to acquire the delivery sinogram during the actual treatment, which partly includes information from the irradiated object. In this study, we try to develop image reconstruction during treatment with helical tomotherapy.
  
  
  RESULTS
  Sinogram data were acquired during helical tomotherapy delivery using an arc-shaped detector array that consists of 576 xenon-gas filled detector cells. In preprocessing, these were normalized with full air-scan data. A software program was developed that reconstructs 3D images during treatment with corrections as; (1) the regions outside the field were masked not to be added in the backprojection (a masking correction), and (2) each voxel of the reconstructed image was divided by the number of the beamlets passing through its voxel (a ray-passing correction). The masking correction produced a reconstructed image, however, it contained streak artifacts. The ray-passing correction reduced this artifact. Although the SNR (the ratio of mean to standard deviation in a homogeneous region) and the contrast of the reconstructed image were slightly improved with the ray-passing correction, use of only the masking correction was sufficient for the visualization purpose.
  
  
  CONCLUSIONS
  The visualization of the treatment area was feasible by using the sinogram in helical tomotherapy. This proposed method would be useful in the treatment verification.
authors.affiliation: Department of Radiology, University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo, Tokyo, Japan. haga-haga@umin.ac.jp.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Haga
authors.affiliation: Department of Radiology, University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo, Tokyo, Japan. nakagawa-rad@umin.ac.jp.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Nakagawa
authors.affiliation: Accuray Incorporated, Sunnyvale, CA, USA. cmaurer@accuray.com.
authors.forename: Calvin
authors.initials: C
authors.lastname: Maurer
authors.affiliation: Accuray Incorporated, Sunnyvale, CA, USA. kruchala@accuray.com.
authors.forename: Ken
authors.initials: K
authors.lastname: Ruchala
authors.affiliation: Accuray Incorporated, Sunnyvale, CA, USA. echao@accuray.com.
authors.forename: Edward
authors.initials: E
authors.lastname: Chao
authors.affiliation: Accuray Incorporated, Sunnyvale, CA, USA. dcasey@accuray.com.
authors.forename: Dylan
authors.initials: D
authors.lastname: Casey
authors.affiliation: Department of Radiology, University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo, Tokyo, Japan. satoshikida1492@yahoo.co.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kida
authors.affiliation: Department of Radiology, University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo, Tokyo, Japan. dousatsu-univtky@umin.ac.jp.
authors.forename: Dousatsu
authors.initials: D
authors.lastname: Sakata
authors.affiliation: Department of Radiology, University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo, Tokyo, Japan. mnak.mp@gmail.com.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Nakano
authors.affiliation: Department of Radiology, University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo, Tokyo, Japan. t.magome@gmail.com.
authors.forename: Taiki
authors.initials: T
authors.lastname: Magome
authors.affiliation: Department of Radiology, University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo, Tokyo, Japan. masutani@hiroshima-cu.ac.jp.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Masutani
mesh_terms: D000465:Algorithms; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*