title: Evaluating the accuracy of the XVI dual registration tool compared with manual soft tissue matching to localise tumour volumes for post-prostatectomy patients receiving radiotherapy.
abstract: BACKGROUND
  Cone beam computerised tomography (CBCT) enables soft tissue visualisation to optimise matching in the post-prostatectomy setting, but is associated with inter-observer variability. This study assessed the accuracy and consistency of automated soft tissue localisation using XVI's dual registration tool (DRT).
  
  
  METHODS
  Sixty CBCT images from ten post-prostatectomy patients were matched using: (i) the DRT and (ii) manual soft tissue registration by six radiation therapists (RTs). Shifts in the three Cartesian planes were recorded. The accuracy of the match was determined by comparing shifts to matches performed by two genitourinary radiation oncologists (ROs). A Bland-Altman method was used to assess the 95% levels of agreement (LoA). A clinical threshold of 3 mm was used to define equivalence between methods of matching.
  
  
  RESULTS
  The 95% LoA between DRT-ROs in the superior/inferior, left/right and anterior/posterior directions were -2.21 to +3.18 mm, -0.77 to +0.84 mm, and -1.52 to +4.12 mm, respectively. The 95% LoA between RTs-ROs in the superior/inferior, left/right and anterior/posterior directions were -1.89 to +1.86 mm, -0.71 to +0.62 mm and -2.8 to +3.43 mm, respectively. Five DRT CBCT matches (8.33%) were outside the 3-mm threshold, all in the setting of bladder underfilling or rectal gas. The mean time for manual matching was 82 versus 65 s for DRT.
  
  
  CONCLUSIONS
  XVI's DRT is comparable with RTs manually matching soft tissue on CBCT. The DRT can minimise RT inter-observer variability; however, involuntary bladder and rectal filling can influence the tools accuracy, highlighting the need for RT evaluation of the DRT match.
authors.affiliation: Department of Radiation Oncology, Princess Alexandra Hospital, Brisbane, Queensland, Australia.
authors.forename: Amelia
authors.initials: A
authors.lastname: Campbell
authors.affiliation: Oncology Mater Centre, Princess Alexandra Hospital, Brisbane, Queensland, Australia.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Owen
authors.affiliation: Department of Radiation Oncology, Princess Alexandra Hospital, Brisbane, Queensland, Australia.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Brown
authors.affiliation: Department of Radiation Oncology, Princess Alexandra Hospital, Brisbane, Queensland, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Pryor
authors.affiliation: QFAB Bioinformatics, University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Anne
authors.initials: A
authors.lastname: Bernard
authors.affiliation: Department of Radiation Oncology, Princess Alexandra Hospital, Brisbane, Queensland, Australia.
authors.forename: Margot
authors.initials: M
authors.lastname: Lehman
mesh_terms: D054893:Cone-Beam Computed Tomography / Q000379:methods*; D003238:Connective Tissue / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D059351:Organ Sparing Treatments / Q000379:methods; D058958:Organs at Risk / Q000528:radiation effects; D010363:Pattern Recognition, Automated / Q000379:methods; D011182:Postoperative Care / Q000379:methods; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000628:therapy*; D018714:Radiotherapy, Adjuvant / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D016896:Treatment Outcome; D047368:Tumor Burden
keywords: CBCT; IGRT; post prostatectomy; radiation oncology; soft tissue