title: [Analysis of megavoltage computed tomography imaging on a helical tomotherapy unit].
abstract: OBJECTIVE
  To evaluate the image quality of megavoltage computed Tomography imaging.
  
  
  METHODS
  The HU uniformity and linearity, image noise, spatial resolution, low contrast resolution and spatial linearity in MVCT mode were evaluated with Catphan 600 phantom, and the factor of pitch was also evaluated. Influencing factors of image quality were also discussed.
  
  
  RESULTS
  The MVCT values depended linearly on the physical density of the sample. The MVCT values uniformity was good. The spatial resolution was 4 lp/cm. The use of an MV Beam for imaging results in the loss of low contrast resolution, but it is sufficient for pretreatment image guidance. The geometric accuracy was good.
  
  
  CONCLUSIONS
  The image quality of MVCT is less than that of KVCT, but is good enough for IGRT.
authors.affiliation: Department of Radiation, PLA General Hospital, Beijing 100853, China.
authors.forename: Xiangkun
authors.initials: X
authors.lastname: Dai
authors.forename: Yunlai
authors.initials: Y
authors.lastname: Wang
authors.forename: Shouping
authors.initials: S
authors.lastname: Xu
authors.forename: Zhongjian
authors.initials: Z
authors.lastname: Ju
authors.forename: Ruigang
authors.initials: R
authors.lastname: Ge
authors.forename: Chuanbin
authors.initials: C
authors.lastname: Xie
authors.forename: Hanshun
authors.initials: H
authors.lastname: Gong
mesh_terms: D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation*; D036542:Tomography, Spiral Computed / Q000295:instrumentation*