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TY - CONF
AU - Wang, K.
AU - Jin, S.
AU - Wang, Z.
AU - Zhang, J.
ED - Koscielniak, Shane
ED - Satogata, Todd
ED - Schaa, Volker RW
ED - Thomson, Jana
TI - Comparison of Water Absorbed Dose for Photons of Linac and Traceability System for Radiotherapy in China
J2 - Proc. of IPAC2018, Vancouver, BC, Canada, April 29-May 4, 2018
C1 - Vancouver, BC, Canada
T2 - International Particle Accelerator Conference
T3 - 9
LA - english
AB - National Institute of Metrology (NIM) developed the standards of the absorbed dose to water for high-energy photon and electron beams, to support the PSDL and SSDL calibration capability in China. After the measurement of absorbed dose to water for 6, 10, and 25 MV photons of linac, NIM took part the BIPM. RI(I).K6 comparison with the Bureau International des Poids et Mesures (BIPM). The tissue phantom ratio (TPR_{20,10}) of 6MV and 10MV photons were measured by IBA CC13 chamber and Keithley 6517B with different output dose of the Linac, and also calculated by the dose ratio (D₂0⁄D₁0) with the formula in IAEA TRS-398 report. TPR_{20,10} measured directly is 0.3% larger than calculated by the dose ratio D₂0⁄D₁0 . The absorbed dose to water is measured by water calorimeter with the combined standard uncertainty of 0.35%. The discrepancy of absorbed dose to water measured separately by open and sealed vessel is 0.2% at 10MV. The K6 comparison was done, the results reported as ratios of the NIM and the BIPM evaluations (and with the combined standard uncertainties given in parentheses), are 0.9917(60) at 6 MV, and 0.9941(59) at 10 MV. The quality correction factor KQ of usual used chamber was measure directly, and it is 0.3%~0.7% smaller than the data in the IAEA TRS-398 report. The typical chamber-to-chamber variations of the dose obtained with the IAEA TRS-277, TRS-398 and AAPM TG-51 were between 0.2% and 1.0% for the different photon beams. The variations of the dose obtained with IAEA TRS-398 and chambers calibrated directly by megavoltage photons were between 0.1% to 0.8%. The new standard can achieve the traceability of water absorbed dose for MV photons and will significantly reduce the uncertainty of ion chamber calibrations for Chinese radiotherapy centers.
PB - JACoW Publishing
CP - Geneva, Switzerland
SP - 537
EP - 539
KW - photon
KW - controls
KW - radiation
KW - linac
KW - electron
DA - 2018/06
PY - 2018
SN - 978-3-95450-184-7
DO - 10.18429/JACoW-IPAC2018-MOPML058
UR - http://jacow.org/ipac2018/papers/mopml058.pdf
ER -