Abstract |
Radiotherapy, radiation dose to critical structures (e.g. fetus, ovaries, testes, thyroid,
pacemaker) outside the primary radiation field must be minimized. In these cases, the
dose delivered outside the primary field (peripheral dose, PD) must be evaluated prior to
the treatment and reduced if necessary. A number of factors-parameters of the treatment
planning influence the PD. In the present study, an inclusive experimental study on the
parameters that influence the PD was completed using a modern linear accelerator
(LINAC). This dependence was evaluated for each of these factors, in order to develop an
applicable method to estimate the PD for various treatments planning. For this purpose,
two dosimetric methods were utilized: a) ionization chamber in a water phantom and b)
thermoluminescent dosimeters (TLDs) in three different anthropomorphic phantoms,
simulating the bodies of 5 and 10 years old children and one of an adult. The first method
was the basic dosimetric system and the second one was used as a validation method for
the PD measurements and the developed method overall. Moreover, a second LINAC
was used to examine whether the developed method is applicable to other LINACs. The
present study resulted in the evaluation of the PD dependence on a number of factorsparameters
of the treatment planning and consequently in the development of a method to
estimate the PD. The TLD measurements verified the credibility of the PD measurements
and the accuracy of the developed method. This method is applicable to other LINACs
and can also be used for the PD estimation in children considering a PD overestimation in
these cases.
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