Algoritmo transgenético para os problemas da geometria e da intensidade em IMRT
Intensity Modulated Radiotherapy (IMRT) is a form of treatment of cancerous diseases in which the patient is irradiated with radiation beams, aiming to eliminate tumor cells while sparing healthy organs and tissues as much as possible. Each beam is divided into beamlets that may emit different ra...
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| Formato: | Dissertação |
| Idioma: | pt_BR |
| Publicado em: |
Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/handle/123456789/32619 |
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| Resumo: | Intensity Modulated Radiotherapy (IMRT) is a form of treatment of cancerous diseases
in which the patient is irradiated with radiation beams, aiming to eliminate tumor cells
while sparing healthy organs and tissues as much as possible. Each beam is divided into
beamlets that may emit different radiation doses. A treatment plan is composed of: (a)
a set of beam directions (angles); (b) the amount of radiation emitted by the beamlets
of each beam; and (c), a radiation delivery sequence. The elaboration of a plan can be
modeled by optimization problems, usually NP-hard, where steps (a), (b) and (c) are
called Geometry, Intensity (or Fluence Map) and Realization problems, respectively. This
work addresses the first two. An evolutionary algorithm is proposed for the joint solution
of these two problems; namely: an hybrid Transgenetic Algorithm. It uses an adaptation
of the -constraint method to compute the fluence map of a set of beams. Linear and
quadratic approximation functions are proposed for a particular type of (non-convex)
function present in radiotherapy optimization: the dose-volume function. Two groups of
computational experiments are carried out, using real cases of liver cancer, to ascertain the
algorithm effectiveness: the first one with the tumor’s dose as constraint, and the second
one with the tumor’s dose as objective function. The results of the objective functions show
that the second technique is more appropriate to achieve better doses in the tumor. Other
results regarding the effectiveness of the approximation functions and the components of
the Transgenetic Algorithm are also discussed. |
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