Page 208 - 00. Complete Version - Progress Report IPEN 2014-2016
P. 208
208 Nuclear Science and Technology | Progress Report
The comparison between Varian AAA try uncertainties below 2 %, validating the re-
and ACUROS XB dose calculation sults. Figure 9 presents the anthropomorphic
algorithms for VMAT treatment planning skull 3D printed phantom.
of brain multiple metastases
3D Phantoms
Figure 9- Landauer
nanoDot
dosimeters and Attenuation coefficient determination
anthropomorphic
skull 3D printed of printed ABS and PLA samples in
phantom. diagnostic radiology standard beams
IAEA code of practice TRS-457 states that stan-
dard phantoms should offer the same primary
The Optically Stimulated Luminescence dosim- attenuation and scatter production as relevant
etry has become one of most used techniques body section of a representative patient. Mate-
for radiation dosimetry nowadays. The “Ala- rial cost, availability and dimensional stability
bama Technique” demonstrates plan quality must also be considered. The goal of this study
and provides a practical, systematic approach was to determine the attenuation coefficient
to the treatment planning technique for single of printed ABS and PLA samples in standard
isocenter cranial radiosurgery with volumetric X-ray beams, verifying if phantoms printed
modulated arc therapy (VMAT) used in meta- with these materials could be an easier-han-
static carcinoma treatments. An anthropomor- dle substitute for PMMA, enabling the creation
phic skull 3D printed phantom was submitted of different designs in an easier and cheaper
to a CT scan and planed five target volumes. In way. Results show that PMMA presents higher
order to compare, two dose calculations were attenuation coefficient, followed by PLA and
performed in the Varian Eclipse with VMAT ABS, which means that thinner PMMA layer
planning with “Alabama technique” using creates higher radiation attenuation.
the Varian’s AAA and Acuros XB algorithms.
The treatment was delivered with a VARIAN Equivalence between Solid Water and printed
True Beam linear accelerator with Multileaf PLA plates for 6 MV clinical photon beam – An
Collimator HD and 6 MV photon beam was assessment using thermoluminescent dosimetry
used. Landauer nanoDot dosimeters were po-
sitioned inside each of the five target volumes Three dimensional models of anatomical
planned and the experimental dosimetry re- structures, produced by rapid prototyping are
sults were compared with the two calculation being adopted for medical application as he-
algorithms. The experimental results using the modynamics studies and maxillofacial surgery
OSLDs show agreement of 97.26 %, 99.12 %, planning. Models with geometrical accuracy
99.99 %, 95.94 % and 98.79 % for the targets 1 can be achieved using medical images as MRI
to 5 respectively for the ACUROS XB calculated or CT and produced using polyurethane, poly-
doses. The findings of this work indicate that lactic acid and epoxy resins. By changing ma-
ACUROS XB calculates more accurate doses terials and densities, it is possible to achieve
compared with AAA, with all the experimen- the desired tissue-equivalence[1]. This work
tal agreements better than 96 %. The intrinsic was developed in order to analyze the equiv-
precision and uncertainty of the InLight sys- alence between the printed PLA and the Solid
tem device is sufficient to sustain the dosime- Water plates by using the thermoluminescence
Instituto de Pesquisas Energéticas e Nucleares