title: Comparison of individual and composite field analysis using array detector for Intensity Modulated Radiotherapy dose verification.
abstract: OBJECTIVE
  To compare the measured and calculated individual and composite field planar dose distribution of Intensity Modulated Radiotherapy plans.
  
  
  METHODS
  The measurements were performed in Clinac DHX linear accelerator with 6 MV photons using Matrixx device and a solid water phantom. The 20 brain tumor patients were selected for this study. The IMRT plan was carried out for all the patients using Eclipse treatment planning system. The verification plan was produced for every original plan using CT scan of Matrixx embedded in the phantom. Every verification field was measured by the Matrixx. The TPS calculated and measured dose distributions were compared for individual and composite fields.
  
  
  CONCLUSIONS
  The percentage of gamma pixel match for the dose distribution patterns were evaluated using gamma histogram. The gamma pixel match was 95-98% for 41 fields (39%) and 98% for 59 fields (61%) with individual fields. The percentage of gamma pixel match was 95-98% for 5 patients and 98% for other 12 patients with composite fields. Three patients showed a gamma pixel match of less than 95%. The comparison of percentage gamma pixel match for individual and composite fields showed more than 2.5% variation for 6 patients, more than 1% variation for 4 patients, while the remaining 10 patients showed less than 1% variation.
  
  
  CONCLUSIONS
  The individual and composite field measurements showed good agreement with TPS calculated dose distribution for the studied patients. The measurement and data analysis for individual fields is a time consuming process, the composite field analysis may be sufficient enough for smaller field dose distribution analysis with array detectors.
authors.affiliation: Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bangalore 560029, India.
authors.forename: Sathiyan
authors.initials: S
authors.lastname: Saminathan
authors.affiliation: Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bangalore 560029, India.
authors.forename: Varatharaj
authors.initials: V
authors.lastname: Chandraraj
authors.affiliation: Bharat Cancer Hospital and Research Center, Mysore, India.
authors.forename: C H
authors.initials: CH
authors.lastname: Sridhar
authors.affiliation: Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bangalore 560029, India.
authors.forename: Ravikumar
authors.initials: R
authors.lastname: Manickam
keywords: Gamma pixel; IMRT; I’matriXX; TPS