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Radiation quality investigations around a neutron therapy beam, using a high‐pressure ionization chamber
Author(s) -
Makrigiorgos G. M.,
Smathers J. B.,
Myers L. T.,
Benedict S. H.
Publication year - 1990
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.596532
Subject(s) - isocenter , ionization chamber , neutron , proton therapy , dosimetry , beam (structure) , ionization , physics , atomic physics , proton , linear energy transfer , equivalent dose , laser beam quality , absorbed dose , nuclear physics , radiation , nuclear medicine , optics , ion , medicine , imaging phantom , quantum mechanics , laser , laser beams
The mean quality factor ( Q ̄) and the dose mean linear energy transfer [LET ( L ̄ D )] a few centimeters outside a neutron therapy beam have been measured using a high‐pressure ionization chamber. Measurements have been carried out in air, 5 and 100 cm outside the treatment field edge on the patient plane for p (46)‐Be neutrons and are compared with the results obtained at the same points with a low‐pressure proportional counter (Rossi counter) and a Bonner spheres system. General agreement is found between these independent methods. The dose equivalent at 5 and 100 cm distances outside the field edge is 2% and 0.4% of the dose equivalent at the isocenter. Measurements were also performed at the same points as a function of proton energy on the Be target. Proton energies of 25–46 MeV on Be were applied. The results indicate increase in the mean quality factor at proton energies below 30 MeV.