title: A practical method of identifying data loss in 4DCT.
abstract: OBJECTIVE
  The design, testing and clinical implementation of a simple quality assurance tool which allows quick and accurate identification of regions of data loss and data interpolation in 4DCT data sets is reported.
  
  
  METHODS
  A 4DCT model, dependent on gantry rotation time and pitch, was developed to allow an understanding of the data collection and reconstruction processes. To test this model, 4DCT scans of a phantom were acquired using a Siemens SOMATOM Sensation 40 slice CT scanner. A radio-opaque rod mounted under the couch top was present during the phantom scans.
  
  
  RESULTS
  The model predicts that periodic regions of data loss occur when the respiration rate drops below a critical value. These results are verified by experimental data. Regions of data loss result in breaks in the imaged radio-opaque rod.
  
  
  CONCLUSIONS
  Regions of data loss in 4DCT data sets can be difficult to detect. Mounting a radio-opaque rod under the couch top allows regions of data loss and data interpolation to be quickly assessed on a patient by patient basis. This quality assurance tool has been successfully implemented into clinical use. The results of this work have implications for quality assurance programmes for 4DCT scanning.
authors: Department of Medical Physics and Clinical Engineering, St James's University Hospital, Leeds, UK. David-W.Smith@leedsth.nhs.uk
authors: David W
authors: DW
authors: Smith
authors: Christopher
authors: C
authors: Dean
authors: John
authors: J
authors: Lilley
mesh_terms: D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D019047:Phantoms, Imaging; D011785:Quality Assurance, Health Care; D011857:Radiographic Image Interpretation, Computer-Assisted; D012119:Respiration