title: Automated detection of patient movement during a CBCT scan based on the projection data.
abstract: OBJECTIVE
  To develop an automated procedure to detect patient motion on the projection images acquired during a cone beam computed tomography (CBCT) scan and to evaluate the method's feasibility on small real-world CBCT images in relation to visual assessment.
  
  
  METHODS
  Based on optical flow theory, software was developed using the sequence of the projection images of a CBCT machine for automated detection of patient motion. Averaged acceleration vectors were used as measurement data and compared with visual assessment of the projection images displayed as video. Seventy-nine CBCT data sets (small field-of-view: 40 mm) from our patient database were selected in a sequential fashion and evaluated with the software.
  
  
  RESULTS
  10 out of 79 (13%) were allocated to a patient movement. A threshold of 0.4 pixel/frame transition was empirically determined as indicating motion by visual assessment of the image sequence. Relative to this standard of reference, the software reached 80% sensitivity versus 67% specificity.
  
  
  CONCLUSIONS
  Optical flow seems to be an efficient concept for automated detection of patient motion on the projection images acquired during a CBCT scan.
authors: Dept. of Oral Surgery (and Oral Radiology), University Medical Center of the Johannes Gutenberg University, Mainz, Germany. Electronic address: rschulze@mail.uni-mainz.de.
authors: Ralf K W
authors: RK
authors: Schulze
authors: Dillstraße 1, 35745 Herborn, Germany.
authors: Michel
authors: M
authors: Michel
authors: Computing for New Media, RheinMain University of Applied Sciences, Wiesbaden, Germany.
authors: Ulrich
authors: U
authors: Schwanecke
mesh_terms: D000465:Algorithms; D016477:Artifacts; D054893:Cone-Beam Computed Tomography; D005240:Feasibility Studies; D006801:Humans; D021621:Imaging, Three-Dimensional; D009068:Movement; D019047:Phantoms, Imaging; D011857:Radiographic Image Interpretation, Computer-Assisted; D012680:Sensitivity and Specificity; D012984:Software; D014741:Video Recording