K M Langen et al 2003 Phys. Med. Biol. 48 1345 doi:10.1088/0031-9155/48/10/308
Measurement of the tissue to A-150 tissue equivalent plastic kerma ratio at two p(66)Be neutron therapy facilities
K M Langen1,4, P J Binns1,5, A N Schreuder1,6, A J Lennox2 and P M Deluca Jr3
Show affiliationsThe ICRU tissue to A-150 tissue equivalent plastic kerma ratio is needed for neutron therapy dosimetry. The current ICRU protocol for neutron dosimetry recommends using a common conversion factor of 0.95 at all high-energy neutron therapy facilities. In an effort to determine facility specific ICRU tissue to A-150 plastic kerma ratios, an experimental approach was pursued. Four low pressure proportional counters that differed in wall materials (i.e. A-150, carbon, zirconium and zirconium-oxide) were used as dosimeters and integral kerma ratios were determined directly in the clinical beam. Measurements were performed at two p(66)Be facilities: iThemba LABS near Cape Town and Fermilab near Chicago. At the iThemba facility the clinical neutron beam is routinely filtered by a flattening and hardening filter combination. The influence of beam filtration on the kerma ratio was evaluated. Using two recent gas-to-wall dose conversion factor (rm,g value) evaluations a mean ICRU tissue to A-150 plastic kerma ratio of 0.93 ± 0.05 was determined for the clinical beam at iThemba LABS. The respective value for the Fermilab beam is 0.95 ± 0.05. The experimentally determined ICRU tissue to A-150 plastic kerma ratios for the two clinical beams are in agreement with theoretical evaluations. Beam filtration reduces the kerma ratio by 3 ± 2%.
- PACS
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87.53.Bn Dosimetry/exposure assessment
87.56.-v Radiation therapy equipment
29.40.Cs Gas-filled counters: ionization chambers, proportional, and avalanche counters
- Subjects
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Accelerators, beams and electromagnetism
- Dates
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Issue 10 (21 May 2003)
Received 20 November 2002
Published 7 May 2003
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Measurement of the tissue to A-150 tissue equivalent plastic kerma ratio at two p(66)Be neutron therapy facilities
K M Langen et al 2003 Phys. Med. Biol. 48 1345
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