title: Image guidance protocols: balancing imaging parameters against scan time.
abstract: OBJECTIVE
  Optimisation of imaging protocols is essential to maximise the use of image-guided radiotherapy. This article evaluates the time for daily online imaging with TomoTherapy® (Accuray®, Sunnyvale, CA), separating mechanical scan acquisition from radiographer-led image matching, to estimate the time required for a clinical research study (VoxTox).
  
  
  METHODS
  Over 5 years, 18 533 treatments were recorded for 3 tumour sites of interest (prostate, head and neck and central nervous system). Data were collected for scan length, number of CT slices, slice thickness, scan acquisition time and image matching time.
  
  
  RESULTS
  The proportion of coarse thickness scans increased over time, with a move of making coarse scans as the default. There was a strong correlation between scan time and scan length. Scan acquisition requires 40 s of processing time. For coarse scans, each additional centimetre requires 8 s for acquisition. Image matching takes approximately 1.5 times as long, so each additional centimetre needs 20 s extra in total. Modest changes to the imaging protocol have minimal impact over the course of the day.
  
  
  CONCLUSIONS
  This work quantified the effect of changes to clinical protocols required for research. The results have been found to be reassuring in the busy National Institutes of Health department.
  
  
  CONCLUSIONS
  This novel method of data collection and analysis provides evidence of the minimal impact of research on clinical turnover. Whilst the data relate specifically to TomoTherapy, some aspects may apply to other platforms in the future.
authors.affiliation: Cancer Research UK VoxTox Research Group, Department of Oncology, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.
authors.forename: A M
authors.initials: AM
authors.lastname: Bates
authors.forename: J E
authors.initials: JE
authors.lastname: Scaife
authors.forename: G S J
authors.initials: GS
authors.lastname: Tudor
authors.forename: R
authors.initials: R
authors.lastname: Jena
authors.forename: M
authors.initials: M
authors.lastname: Romanchikova
authors.forename: J C
authors.initials: JC
authors.lastname: Dean
authors.forename: A C F
authors.initials: AC
authors.lastname: Hoole
authors.forename: M P D
authors.initials: MP
authors.lastname: Simmons
authors.forename: N G
authors.initials: NG
authors.lastname: Burnet
mesh_terms: D002985:Clinical Protocols; D006801:Humans; D008297:Male; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014481:United States