Page 206 - 00. Complete Version - Progress Report IPEN 2014-2016

206 Nuclear Science and Technology | Progress Report

curves to 12 MeV electrons presented a lin- cipal target volumes considered like tumors
ear behavior for doses from LDL up to 5 Gy. to be treated and other three cavities to mea-
All repeatability values are better than +3.5%. sure the scattered radiation dose was devel-
CaSO4:Dy dosimeters showed maximum vari- oped to carry out the measures Fig. 6. The dos-
ation of TL sensitivity relative to 60Co of 11.6% es evaluated to the tumor simulators cavities
between solid water and PMMA phantoms and using LiF:Mg,Ti dosimeters corresponding to
microLiF:Mg,Ti dosimeters showed maximum the estimated doses given by IMRT planning
variation of TL sensitivity relative to 60Co of and the repeatability of TL responses is better
9.5% to liquid water and solid water phan- than + 4.12%, lower than 5% acceptable for ra-
toms. According to the results, the phantom diation therapy. The scattered radiation doses
material affected the electron spectrum inci- received by structures 3, 4 and 5 correspond-
dent on the detector and altered the response ed on average to 16.14% of the highest dose
of the dosimeters to 12 MeV clinical electron received by the structure 1, according to the
beam using microLiF:Mg,Ti and CaSO4:Dy as planning. The LiF:Mg,Ti dosimeters demon-
thermoluminescent detectors. strated to have good accuracy in all measures
of IMRT planning. Comparing the doses calcu-
TL and OSL dose response using a PMMA lated by Al2O3:C dosimeters using OSL tech-
phantom for IMRT technique quality assurance nique with the doses provided by the planning
system, it was observed that the dose for the
Figure 6. PMMA
phantom developed cavity 1 was underestimated
to IMRT technique
quality assurance
Three-dimensional dosimetric verification
system using Fricke gel solution applied to
verification of Volumetric Modulated Arc
Radiation Therapy (VMAT) in the treatments
with respiration target movement

The principle of IMRT is to treat a patient from Volumetric Modulated Arc Therapy (VMAT) is
a number of different directions (or contin- one of the methods most commonly used in
uous arcs) with beams of non-uniform flu- teletherapy to treat cancer. The various tech-
ences, which have been optimized to deliver nological advances and the evolution of treat-
a high dose to the target volume and an ac- ment techniques made the VMAT as one of the
ceptably low dose to the surrounding normal state of the art methods for the treatment of
structures. This study had as objective to pro- some cancers. Such advances require quality
vide information to the physicist regarding control of these tools in order to ensure that
the application of different dosimeters type, the entire treatment process is satisfactory and
phantoms and analysis technique for Intensi- accurate. To date, the community lacks an ex-
ty Modulated Radiation Therapy (IMRT) dose perimental system capable of evaluating, con-
distributions evaluation. The measures were sidering the uncertainty levels, if the comput-
performed using dosimeters of LiF:Mg,Ti and erized planning systems are able to consider
Al2O3:C evaluated by techniques of thermo- the movement of targets in the treatments
luminescent (TL) and Optically Stimulated Lu- with VMAT. In this work, it was projected and
minescence (OSL). A polymethylmethacrylate developed a Fricke Xylenol Gel phantom capa-
(PMMA) phantom with five cavities, two prin- ble of measuring the differences introduced

Instituto de Pesquisas Energéticas e Nucleares