Verification of absorbed dose determined with plane-parallel chambers in clinical electron beams following AAPM Task Group 39 protocol using ferrous sulphate dosimetry.
The absorbed dose values determined with the Exradin and PTW-Markus plane-parallel chambers were compared to the values obtained with the ferrous sulphate dosimetry for a number of the Philips SL25 and the Therac 20 electron beams. For the plane-parallel chambers, the cavity-gas calibration factor Ngaspp, was derived by a direct comparison with a calibrated cylindrical chamber using the three different calibration methods as proposed by the newly published AAPM TG 39 protocol. For the ferrous sulphate dosimetry, an epsilon mG value of 352 x 10(-6) m-2 kg-1 Gy-1 was adopted from ICRU Report No. 35. The average ratio of the dose values determined with the plane-parallel chambers and the dose values determined with the Fricke dosimetry system was 1.001 +/- 1.4%. These measurements are consistent with the AAPM TG 39 protocol.
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Department of Radiation Oncology, University of Louisville, Brown Cancer Center, Kentucky 40202, USA.
Li
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Almond
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Guan
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D055592:Biophysical Phenomena; D001703:Biophysics; D002985:Clinical Protocols; D004583:Electrons / Q000627:therapeutic use*; D005296:Ferrous Compounds; D006801:Humans; D019047:Phantoms, Imaging; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods* / Q000706:statistics & numerical data; D013679:Technology, Radiologic / Q000706:statistics & numerical data
D005296:Ferrous Compounds; C020748:ferrous sulfate