title: A multi-institutional dosimetry audit of rotational intensity-modulated radiotherapy.
abstract: BACKGROUND
  Rotational IMRT (VMAT and Tomotherapy) has now been implemented in many radiotherapy centres. An audit to verify treatment planning system modelling and treatment delivery has been undertaken to ensure accurate clinical implementation.
  
  
  METHODS
  34 institutions with 43 treatment delivery systems took part in the audit. A virtual phantom planning exercise (3DTPS test) and a clinical trial planning exercise were planned and independently measured in each institution using a phantom and array combination. Point dose differences and global gamma index (γ) were calculated in regions corresponding to PTVs and OARs.
  
  
  RESULTS
  Point dose differences gave a mean (±sd) of 0.1±2.6% and 0.2±2.0% for the 3DTPS test and clinical trial plans, respectively. 34/43 planning and delivery combinations achieved all measured planes with >95% pixels passing γ<1 at 3%/3mm and rose to 42/43 for clinical trial plans. A statistically significant difference in γ pass rates (p<0.01) was seen between planning systems where rotational IMRT modelling had been designed for the manufacturer's own treatment delivery system and those designed independently of rotational IMRT delivery.
  
  
  CONCLUSIONS
  A dosimetry audit of rotational radiotherapy has shown that TPS modelling and delivery for rotational IMRT can achieve high accuracy of plan delivery.
authors.affiliation: Department of Medical Physics, Royal Surrey County Hospital, Guildford, UK; National Physical Laboratory, London, UK; NCRI Radiotherapy Trials Quality Assurance Group, UK. Electronic address: catharine.clark@nhs.net.
authors.forename: Catharine H
authors.initials: CH
authors.lastname: Clark
authors.affiliation: Department of Medical Physics, Royal Surrey County Hospital, Guildford, UK; Centre for Nuclear and Radiation Physics, University of Surrey, UK.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Hussein
authors.affiliation: NCRI Radiotherapy Trials Quality Assurance Group, UK; Mount Vernon Hospital, Northwood, London, UK.
authors.forename: Yatman
authors.initials: Y
authors.lastname: Tsang
authors.affiliation: National Physical Laboratory, London, UK.
authors.forename: Russell
authors.initials: R
authors.lastname: Thomas
authors.affiliation: NCRI Radiotherapy Trials Quality Assurance Group, UK; Mount Vernon Hospital, Northwood, London, UK.
authors.forename: Dean
authors.initials: D
authors.lastname: Wilkinson
authors.affiliation: National Physical Laboratory, London, UK.
authors.forename: Graham
authors.initials: G
authors.lastname: Bass
authors.affiliation: National Physical Laboratory, London, UK.
authors.forename: Julia
authors.initials: J
authors.lastname: Snaith
authors.affiliation: National Physical Laboratory, London, UK.
authors.forename: Clare
authors.initials: C
authors.lastname: Gouldstone
authors.affiliation: Christie Hospital, Manchester, UK; Institute of Physics and Engineering in Medicine, York, UK.
authors.forename: Steve
authors.initials: S
authors.lastname: Bolton
authors.affiliation: National Physical Laboratory, London, UK.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Nutbrown
authors.affiliation: NCRI Radiotherapy Trials Quality Assurance Group, UK; Mount Vernon Hospital, Northwood, London, UK.
authors.forename: Karen
authors.initials: K
authors.lastname: Venables
authors.affiliation: Department of Medical Physics, Royal Surrey County Hospital, Guildford, UK; Centre for Nuclear and Radiation Physics, University of Surrey, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Nisbet
mesh_terms: D008485:Medical Audit; D010347:Patient Care Planning; D019047:Phantoms, Imaging; D011874:Radiometry; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000592:standards
keywords: Audit; Detector arrays; IMRT; VMAT