Radiation quality investigations around a neutron therapy beam, using a high-pressure ionization chamber.
The mean quality factor (Q) and the dose mean linear energy transfer [LET (LD)] 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 neurons 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.
Makrigiorgos
G M
GM
Department of Medical Physics, University of Athens, Greece.
Smathers
J B
JB
Myers
L T
LT
Benedict
S H
SH
D006801:Humans; D009502:Neutrons; D011874:Radiometry / Q000295:instrumentation*; D011882:Radiotherapy, High-Energy; D013679:Technology, Radiologic