title: Dosimetric intercomparison for multicenter clinical trials using a patient-based anatomic pelvic phantom.
abstract: OBJECTIVE
  To assess dose delivery accuracy to clinically significant points in a realistic patient geometry for two separate pelvic radiotherapy scenarios.
  
  
  METHODS
  An inhomogeneous pelvic phantom was transported to 36 radiotherapy centers in Australia and New Zealand. The phantom was treated according to Phase III rectal and prostate trial protocols. Point dose measurements were made with thermoluminescent dosimeters (TLDs) and an ionisation chamber. Comprehensive site-demographic, treatment planning, and physical data were collected for correlation with measurement outcomes.
  
  
  RESULTS
  Dose delivery to the prescription point for the rectal treatment was consistent with planned dose (mean difference between planned and measured dose - 0.1 ± 0.3% std err). Dose delivery in the region of the sacral hollow was consistently higher than planned (+1.2 ± 0.2%). For the prostate treatment, dose delivery to the prostate volume was consistent with planned doses (-0.49 ± 0.2%) and planned dose uniformity, though with a tendency to underdose the PTV at the prostate-rectal border. Measured out-of-field doses were significantly higher than planned.
  
  
  CONCLUSIONS
  A phantom based on realistic anatomy and heterogeneity can be used to comprehensively assess the influence of multiple aspects of the radiotherapy treatment process on dose delivery. The ability to verify dose delivery for two trials with a single phantom was advantageous.
authors: Department of Radiation Oncology, Sir Charles Gairdner Hospital, Western Australia 6009, Australia. Martin.Ebert@health.wa.gov.au
authors: M A
authors: MA
authors: Ebert
authors: K M
authors: KM
authors: Harrison
authors: S J
authors: SJ
authors: Howlett
authors: D
authors: D
authors: Cornes
authors: M
authors: M
authors: Bulsara
authors: C S
authors: CS
authors: Hamilton
authors: T
authors: T
authors: Kron
authors: D J
authors: DJ
authors: Joseph
authors: J W
authors: JW
authors: Denham
mesh_terms: D000704:Analysis of Variance; D002986:Clinical Trials as Topic; D006801:Humans; D008297:Male; D015337:Multicenter Studies as Topic; D010388:Pelvis / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D019047:Phantoms, Imaging; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation*; D011878:Radiotherapy / Q000379:methods*; D014057:Tomography, X-Ray Computed