title: Multicentre validation of IMRT pre-treatment verification: comparison of in-house and external audit.
abstract: OBJECTIVE
  We performed a multicentre intercomparison of IMRT optimisation and dose planning and IMRT pre-treatment verification methods and results. The aims were to check consistency between dose plans and to validate whether in-house pre-treatment verification results agreed with those of an external audit.
  
  
  METHODS
  Participating centres used two mock cases (prostate and head and neck) for the intercomparison and audit. Compliance to dosimetric goals and total number of MU per plan were collected. A simple quality index to compare the different plans was proposed. We compared gamma index pass rates using the centre's equipment and methodology to those of an external audit.
  
  
  RESULTS
  While for the prostate case, all centres fulfilled the dosimetric goals and plan quality was homogeneous, that was not the case for the head and neck case. The number of MU did not correlate with the plan quality index. Pre-treatment verifications results of the external audit did not agree with those of the in-house measurements for two centres: being within tolerance for in-house measurements and unacceptable for the audit or the other way round.
  
  
  CONCLUSIONS
  Although all plans fulfilled dosimetric constraints, plan quality is highly dependent on the planner expertise. External audits are an excellent tool to detect errors in IMRT implementation and cannot be replaced by intercomparison using results obtained by centres.
authors: Servei de Radiofísica i Radioprotecció, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain. Electronic address: njornet@santpau.cat.
authors: Núria
authors: N
authors: Jornet
authors: Servei de Radiofísica i Radioprotecció, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.
authors: Pablo
authors: P
authors: Carrasco
authors: Servei de Física, Hospital Vall d'Hebró, Barcelona, Spain.
authors: Mercè
authors: M
authors: Beltrán
authors: Servei d'Oncologia Radioteràpica, Hospital Quirón, Barcelona, Spain.
authors: Juan Francisco
authors: JF
authors: Calvo
authors: Servei d'Oncologia Radioteràpica, Clinica Teknon, Barcelona, Spain.
authors: Lluís
authors: L
authors: Escudé
authors: Servei de Física, Hospital Sant Joan, Reus, Spain.
authors: Victor
authors: V
authors: Hernández
authors: Servei d'Oncologia Radioteràpica, Hospital de l'Esperança, Barcelona, Spain.
authors: Jaume
authors: J
authors: Quera
authors: Servei de Física, Hospital Vall d'Hebró, Barcelona, Spain.
authors: Jordi
authors: J
authors: Sáez
mesh_terms: D054869:Clinical Audit / Q000379:methods* / Q000706:statistics & numerical data*; D006258:Head and Neck Neoplasms / Q000532:radiotherapy; D006801:Humans; D008297:Male; D058958:Organs at Risk; D019047:Phantoms, Imaging; D011471:Prostatic Neoplasms / Q000532:radiotherapy; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods* / Q000592:standards* / Q000706:statistics & numerical data; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods* / Q000592:standards* / Q000706:statistics & numerical data; D015203:Reproducibility of Results
keywords: Audit; IMRT; Quality assurance