title: The implementation of in vivo dosimetry in a small radiotherapy department.
abstract: OBJECTIVE
  In vivo dosimetry has been shown in a number of evaluation studies, generally carried out in larger academic centres, to be a reliable method of checking the overall treatment accuracy. The object of this study was to investigate whether it was possible and useful to perform in vivo dosimetry in a small radiotherapy department and to detect if there were any systematic errors in the overall treatment set-up.
  
  
  METHODS
  All patients were treated on a cobalt-60 unit equipped with a verification system. Six hundred fifty entrance dose measurements were performed with silicon diodes.
  
  
  RESULTS
  The analysis showed a mean deviation of -1.3%. This negative deviation was mainly due to the mean deviation obtained in the treatment of head and neck (-1.6%) or breast (-2.5%) cancer patients. The results for pelvic or lung irradiation showed almost no deviation (-0.8 to 0.43%). Further investigation showed that the negative values for head and neck or breast irradiation were due to the irradiation technique; the lack of scattering material causes a reduction of the dose at the reference point, which is not taken into consideration by the treatment planning system. By performing in vivo dosimetry, we were also able to detect two large errors in 650 measurements and could prevent erroneous treatment.
  
  
  CONCLUSIONS
  Even when the overall treatment set-up is very accurate, in vivo dosimetry is very useful in a small department since only a small effort can detect and prevent errors.
authors.affiliation: Department of Radiotherapy, St. Elisabeth Hospital, Turnhout, Belgium.
authors.forename: M
authors.initials: M
authors.lastname: Voordeckers
authors.forename: H
authors.initials: H
authors.lastname: Goossens
authors.forename: J
authors.initials: J
authors.lastname: Rutten
authors.forename: W
authors.initials: W
authors.lastname: Van den Bogaert
mesh_terms: D003037:Cobalt Radioisotopes / Q000008:administration & dosage; D005240:Feasibility Studies; D006284:Health Plan Implementation; D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy; D011785:Quality Assurance, Health Care / Q000592:standards; D011872:Radiology Department, Hospital; D011878:Radiotherapy / Q000592:standards*; D011879:Radiotherapy Dosage; D011881:Radiotherapy, Computer-Assisted / Q000379:methods / Q000592:standards*; D011882:Radiotherapy, High-Energy; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013679:Technology, Radiologic / Q000295:instrumentation
chemical_list: D003037:Cobalt Radioisotopes