title: The use of plane-parallel chambers in electron dosimetry without any cross-calibration.
abstract: Current dosimetry protocols from AAPM, DIN and IAEA recommend a cross-calibration for plane-parallel chambers against a calibrated thimble chamber for electron dosimetry. The rationale for this is the assumed chamber-to-chamber variation of plane-parallel chambers and the large uncertainty in the wall perturbation factor (p(wall)60Co)pp at 60Co for plane-parallel chambers. We have confirmed the results of other authors that chamber-to-chamber variation of the investigated chambers of types Roos, Markus, Advanced Markus and Farmer is less than 0.3%. Starting with a calibration factor for absorbed dose to water and on the basis of the three dosimetry protocols AAPM TG-51, DIN 6800-2 (slightly modified) and IAEA TRS-398, values for (p(wall)60Co)Roos of 1.024 +/- 0.005, (p(wall)60Co)Markus of 1.016 +/- 0.005 and (p(wall)60Co)Advanced Markus of 1.014 +/- 0.005 have been determined. In future this will permit electron dosimetry with the above-listed plane-parallel chambers having a calibration factor N(D, w)60Co without the necessity for cross-calibration against a thimble chamber.
authors.affiliation: Abteilung für Medizinische Physik, Universitätsklinikum Tübingen, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Christ
authors.forename: S
authors.initials: S
authors.lastname: Dohm
authors.forename: G
authors.initials: G
authors.lastname: Bruggmoser
authors.forename: E
authors.initials: E
authors.lastname: Schüle
mesh_terms: D002138:Calibration; D003037:Cobalt Radioisotopes; D004583:Electrons; D011874:Radiometry / Q000379:methods*; D011878:Radiotherapy / Q000295:instrumentation*
chemical_list: D003037:Cobalt Radioisotopes