Rbe for cell survival at different positions in collimated neutron beams in relation to differences in lineal energy spectra
conference paper
In therapeutical applications of ionizing radiations from external sources, the volume of irradiated tissue must generally be restricted as much as possible to the tumour area; consequently, collimated beams should be employed. Due to scattering and absorption interactions of the radiation with the materials of the beam-restricting devices, the output spectrum of the collimated radiation will not be identical to an undisturbed 'free-in-air' spectrum of the source. Likewise, changes in the particle spectrum will occur with penetration depth of the radiation in the patient. These alterations in spectrum were determined for positions in and outside collimated beams of 15, 6.5 and 0.51 MeV neutrons with a tissue-equivalent proportional counter. No significant variations in the measured fractional dose distributions were observed for positions in the beam. For positions outside the beam behind the shielding, the fractional dose distributions for 15 and 6.5 MeV neutrons showed increasing contributions of gamma rays and of attenuated and scattered neutrons.
In relation to this study of spectrum variations, the changes in relative biological effectiveness (r.b.e.) for cell survival at the different positions of the collimated 6.5 and 15 MeV neutron beams were determined. No significant changes in r.b.e. were observed for positions in and outside the beam. These results are discussed in relation to the microdosimetric data.
In relation to this study of spectrum variations, the changes in relative biological effectiveness (r.b.e.) for cell survival at the different positions of the collimated 6.5 and 15 MeV neutron beams were determined. No significant changes in r.b.e. were observed for positions in and outside the beam. These results are discussed in relation to the microdosimetric data.
TNO Identifier
353173
ISBN
0-906346-02-9
Publisher
International Atomic Energy Agency (IAEA)
Source title
6th Symposium on microdosimetry, 22-26 May 1978, Brussels, Belgium
Editor(s)
Booz, J.
Ebert, H.G.
Ebert, H.G.
Place of publication
Vienna
Pages
507-516
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