title: Long-term stability of radiotherapy dosimeters calibrated at the Polish Secondary Standard Dosimetry Laboratory.
abstract: Unidos 10001, Unidos E (10008/10009) and Dose 1 electrometers from 14 radiotherapy centres were calibrated 3-4 times over a long period of time, together with Farmer type (PTW 30001, 30013, Nuclear Enterprises 2571 and Scanditronix-Wellhofer FC65G) cylindrical ionization chambers and plane-parallel type chambers (PTW Markus 23343 and Scanditronix-Wellhofer PPC05). On the basis of the long period of repetitive establishing of calibration coefficients for the same electrometers and ionization chambers, the accuracy of electrometers and the long-term stability of ionization chambers were examined. All measurements were carried out at the same laboratory, by the same staff, according to the same IAEA recommendations. A good accuracy and long-term stability of the dosimeters used in Polish radiotherapy centres was observed. These values were within 0.1% for electrometers and 0.2% for the chambers with electrometers. Furthermore, these values were not observed to vary over time. The observations confirm the opinion that the requirement of calibration of the dosimeters more often than every 2 years is not justified.
authors.affiliation: Department of Medical Physics, The Maria Skłodowska-Curie Memorial Cancer Centre and Institute of Oncology, Roentgena 5, 02-781 Warsaw, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Ulkowski
authors.affiliation: Department of Medical Physics, The Maria Skłodowska-Curie Memorial Cancer Centre and Institute of Oncology, Roentgena 5, 02-781 Warsaw, Poland. Electronic address: w.bulski@zfm.coi.pl.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Bulski
authors.affiliation: Department of Medical Physics, The Maria Skłodowska-Curie Memorial Cancer Centre and Institute of Oncology, Roentgena 5, 02-781 Warsaw, Poland. Electronic address: k.chelminski@zfm.coi.pl.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Chełmiński
mesh_terms: D002138:Calibration / Q000592:standards*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007753:Laboratories / Q000592:standards*; D011044:Poland; D011874:Radiometry / Q000295:instrumentation* / Q000592:standards*; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000295:instrumentation* / Q000592:standards*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: SSDL; calibration coefficients; dosimeters; ionization chambers; long-term stability