title: An interprojection sensor fusion approach to estimate blocked projection signal in synchronized moving grid-based CBCT system.
abstract: OBJECTIVE
  A preobject grid can reduce and correct scatter in cone beam computed tomography (CBCT). However, half of the signal in each projection is blocked by the grid. A synchronized moving grid (SMOG) has been proposed to acquire two complimentary projections at each gantry position and merge them into one complete projection. That approach, however, suffers from increased scanning time and the technical difficulty of accurately merging the two projections per gantry angle. Herein, the authors present a new SMOG approach which acquires a single projection per gantry angle, with complimentary grid patterns for any two adjacent projections, and use an interprojection sensor fusion (IPSF) technique to estimate the blocked signal in each projection. The method may have the additional benefit of reduced imaging dose due to the grid blocking half of the incident radiation.
  
  
  METHODS
  The IPSF considers multiple paired observations from two adjacent gantry angles as approximations of the blocked signal and uses a weighted least square regression of these observations to finally determine the blocked signal. The method was first tested with a simulated SMOG on a head phantom. The signal to noise ratio (SNR), which represents the difference of the recovered CBCT image to the original image without the SMOG, was used to evaluate the ability of the IPSF in recovering the missing signal. The IPSF approach was then tested using a Catphan phantom on a prototype SMOG assembly installed in a bench top CBCT system.
  
  
  RESULTS
  In the simulated SMOG experiment, the SNRs were increased from 15.1 and 12.7 dB to 35.6 and 28.9 dB comparing with a conventional interpolation method (inpainting method) for a projection and the reconstructed 3D image, respectively, suggesting that IPSF successfully recovered most of blocked signal. In the prototype SMOG experiment, the authors have successfully reconstructed a CBCT image using the IPSF-SMOG approach. The detailed geometric features in the Catphan phantom were mostly recovered according to visual evaluation. The scatter related artifacts, such as cupping artifacts, were almost completely removed.
  
  
  CONCLUSIONS
  The IPSF-SMOG is promising in reducing scatter artifacts and improving image quality while reducing radiation dose.
authors.affiliation: Department of Radiation Oncology, Georgia Regents University, Augusta, Georgia 30912.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology, Duke University, Durham, North Carolina 27710.
authors.forename: Lei
authors.initials: L
authors.lastname: Ren
authors.affiliation: Department of Radiation Oncology, Georgia Regents University, Augusta, Georgia 30912.
authors.forename: Vic
authors.initials: V
authors.lastname: Kong
authors.affiliation: Department of Radiation Oncology, Duke University, Durham, North Carolina 27710.
authors.forename: William
authors.initials: W
authors.lastname: Giles
authors.affiliation: Department of Radiation Oncology, Duke University, Durham, North Carolina 27710.
authors.forename: You
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology, Georgia Regents University, Augusta, Georgia 30912 and Department of Radiology, Georgia Regents University, Augusta, Georgia 30912.
authors.forename: Jian-Yue
authors.initials: JY
authors.lastname: Jin
mesh_terms: D054893:Cone-Beam Computed Tomography / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D009038:Motion; D019047:Phantoms, Imaging; D012044:Regression Analysis; D012542:Scattering, Radiation; D059629:Signal-To-Noise Ratio