title: A methodology for dosimetry audit of rotational radiotherapy using a commercial detector array.
abstract: OBJECTIVE
  To develop a methodology for the use of a commercial detector array in dosimetry audits of rotational radiotherapy.
  
  
  METHODS
  The methodology was developed as part of the development of a national audit of rotational radiotherapy. Ten cancer centres were asked to create a rotational radiotherapy treatment plan for a three-dimensional treatment-planning-system (3DTPS) test and audited. Phantom measurements using a commercial 2D ionisation chamber (IC) array were compared with measurements using 0.125 cm(3) IC, Gafchromic film and alanine pellets in the same plane. Relative and absolute gamma index (γ) comparisons were made for Gafchromic film and 2D-Array planes, respectively.
  
  
  RESULTS
  Comparisons between individual detectors within the 2D-Array against the corresponding IC and alanine measurement showed a statistically significant concordance correlation coefficient (both ρc>0.998, p<0.001) with mean difference of -1.1 ± 1.1% and -0.8 ± 1.1%, respectively, in a high dose PTV. In the γ comparison between the 2D-Array and film it was that the 2D-Array was more likely to fail planes where there was a dose discrepancy due to the absolute analysis performed.
  
  
  CONCLUSIONS
  It has been found that using a commercial detector array for a dosimetry audit of rotational radiotherapy is suitable in place of standard systems of dosimetry.
authors.affiliation: Department of Medical Physics, Royal Surrey County Hospital, Guildford, UK. m.hussein@nhs.net
authors.forename: Mohammad
authors.initials: M
authors.lastname: Hussein
authors.forename: Yatman
authors.initials: Y
authors.lastname: Tsang
authors.forename: Russell A S
authors.initials: RA
authors.lastname: Thomas
authors.forename: Clare
authors.initials: C
authors.lastname: Gouldstone
authors.forename: David
authors.initials: D
authors.lastname: Maughan
authors.forename: Julia A D
authors.initials: JA
authors.lastname: Snaith
authors.forename: Steven C
authors.initials: SC
authors.lastname: Bolton
authors.forename: Andrew
authors.initials: A
authors.lastname: Nisbet
authors.forename: Catharine H
authors.initials: CH
authors.lastname: Clark
mesh_terms: D005373:Film Dosimetry; D006801:Humans; D008485:Medical Audit / Q000379:methods*; D009369:Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D012399:Rotation
keywords: 2D-Array; Detector arrays; Dosimetry audit; Rotational radiotherapy; Tomotherapy; VMAT