Determination of absorbed dose with two types of clinically employed tissue equivalent ionization chambers in fast neutron beams
conference paper
Measurements were performed for different phantom materials with two types of tissue equivalent ionization chambers recommended for neutron radiotherapy, using several chambers of each type. Neutrons produced by the d+D, d+T and d(50)+Be reactions were used for the measurements. The chambers were calibrated free-in-air at a 60Co gamma-ray source. All measurements were analysed using the same mathematical procedure including correction factors for loss of ionization due to recombination and for displacement of the effective point of measurement.
The measurements in water and tissue equivalent liquid showed maximum differences in absorbed dose values of up to about 4 percent at 15 cm depth in-phantom for d(50)+Be neutrons.
For the acrylic plastic phantom, the absorbed dose values obtained with the different chambers in the 60Co gamma-ray beam are not significantly different. In general the results in the neutron beams show differences of about 1 percent, however, between two specific chambers a maximum difference of 3.3 percent has been observed. Systematic uncertainties can be reduced by calibration of the tissue equivalent ionization chambers in a standard neutron field instead of using a photon beam.
The measurements in water and tissue equivalent liquid showed maximum differences in absorbed dose values of up to about 4 percent at 15 cm depth in-phantom for d(50)+Be neutrons.
For the acrylic plastic phantom, the absorbed dose values obtained with the different chambers in the 60Co gamma-ray beam are not significantly different. In general the results in the neutron beams show differences of about 1 percent, however, between two specific chambers a maximum difference of 3.3 percent has been observed. Systematic uncertainties can be reduced by calibration of the tissue equivalent ionization chambers in a standard neutron field instead of using a photon beam.
TNO Identifier
353131
Source title
4th symposium on neutron dosimetry, Munich-Neuherberg, GE, 1-5 June 1981
Editor(s)
Burger, G.
Ebert, H.G.
Ebert, H.G.
Pages
361-372
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