et al.. Radiotherapy out-of-field dosimetry: Experimental and computational results for photons in a water tank. Radiation Measurements, Elsevier, 2013, 57, pp.Radiotherapy out-of-field dosimetry: Experimental and computational results for photons in a water tank, Radiation Measurements (2013), Highlights: Dosimeters based on OSL, TLD and RPL have been compared for radiotherapy purposes.  Irradiations have been performed in a water phantom located in and out of the beam.  Doses have been studied for three radiation quantities, 6, 12 and 20 MV.  Water and collimator scatter and leakage doses out of the beam have been evaluated.

During the Euramet project JRP7 ‘External Beam Cancer Therapy’, PTB and LNE–LNHB used primary standards to determine the absorbed dose to water under IMRT conditions (in small fields). PTB used a water calorimeter to determine the absorbed-dose-to-water references in 6 MV and 10 MV beams for field sizes of 10 cm × 10 cm and 3 cm × 3 cm while LNE–LNHB used graphite calorimeters in 6 MV and 12 MV beams for field sizes of 10 cm × 10 cm, 4 cm × 4 cm and 2 cm × 2 cm. The purpose of this study is to compare PTB and LNE–LNHB new absorbed-dose-to-water references. LNE–LNHB sent an Exradin A1SL ionization chamber traceable to its primary standard to the PTB for calibration in 60Co and in linac beams and PTB sent a PTW 31010 ionization chamber traceable to its primary standard to LNE–LNHB for calibration in 60Co and in linac beams. Calculated Sw,air will be used as beam quality specifier for the ionization chamber comparison at different field sizes. The standard uncertainties (k = 1) of PTB and LNE–LNHB calibration coefficients lie respectively between 0.25% (60Co) and 0.40% (linac) and between 0.29% and 0.46%. PTB and LNE–LNHB absorbed-dose-to-water references developed for this project, based respectively on water calorimetry and on graphite calorimetry, agree within 1.5 standard deviations for field size of 10 cm × 10 cm down to 2 cm × 2 cm and for beams of 6 MV to 10 MV.

A comparison of the dosimetry for accelerator photon beams was carried out between the Laboratoire National de Métrologie et d'Essais -Laboratoire National Henri Becquerel (LNE-LNHB) and the Bureau International des Poids et Mesures (BIPM) in March 2012. The comparison was based on the determination of absorbed dose to water for three radiation qualities at the LNE-LNHB. The comparison result, reported as a ratio of the LNE-LNHB and the BIPM evaluations, is 0.995 at 6 MV and 12 MV; 0.994 at 20 MV, with a combined standard uncertainty of 5 parts in 10 3 at all three energies. This result is the fourth in the ongoing BIPM.RI(I)-K6 series of comparisons.