[show abstract][hide abstract] ABSTRACT: This paper presents the application of a computational methodology for optimizing the conversion of medical tomographic images in voxel anthropomorphic models for simulation of radiation transport using the MCNP code. A computational system was developed for digital image processing that compresses the information from the DICOM medical image before it is converted to the Scan2MCNP software input file for optimization of the image data. In order to validate the computational methodology, a radiosurgery treatment simulation was performed using the Alderson Rando phantom and the acquisition of DICOM images was performed. The simulation results were compared with data obtained with the BrainLab planning system. The comparison showed good agreement for three orthogonal treatment beams of (60)Co gamma radiation. The percentage differences were 3.07%, 0.77% and 6.15% for axial, coronal and sagital projections, respectively.
Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 09/2011; 70(1):144-8. · 1.09 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Brazilian Institute of Radiation Protection and Dosimetry (IRD/CNEN) carried out quality assurance regulatory audits in Brazilian radiotherapy facilities from 1995 to 2007. In this work, the set of data collected from 195 radiotherapy facilities that use high-energy photon beams are analyzed. They include results from audits in linear electron accelerators and/or Co-60 units. The inspectors of IRD/CNEN performed the dosimetry of high-energy radiotherapy photon beams according to the IAEA dosimetry protocols TRS 277 and TRS 398, and the values of measurements were compared to stated values. Other aspects of radiological protection were checked during on-site audits such as calibration certification of clinical dosimeters and portable monitors, existence and use of check source, use of barometer and thermometer, individual dose registry and training of staff. It was verified that no check source was available in 38% of the visited facilities; the training of personnel was not adequate in 9% of the facilities and the registry of accumulated individual doses was not being done in 6% of the facilities. Measurements of absorbed dose have indicated deviations in the range ± 3% for 67.6% of the cobalt-60 units and 79.6% of medical linear accelerators; 18.5% of Co-60 irradiators and 9.6% of linear accelerators presented deviations in the range 3% < δ ≤ 5%. Finally, 13.9% of Co-60 facilities and 10.8% of linear accelerator facilities presented dosimetry deviations above 5%. The effort in dosimetric quality control performed by IRD/CNEN audits has yielded positive changes that make radiation treatment facilities more reliable.
Journal of Applied Clinical Medical Physics 01/2011; 12(2):3330. · 0.96 Impact Factor
[show abstract][hide abstract] ABSTRACT: The purpose of this study is to investigate the influence of lung heterogeneity inside a soft tissue phantom on percentage depth dose (PDD). PDD curves were obtained experimentally using LiF:Mg,Ti (TLD-100) thermoluminescent detectors and applying Eclipse treatment planning system algorithms Batho, modified Batho (M-Batho or BMod), equivalent TAR (E-TAR or EQTAR), and anisotropic analytical algorithm (AAA) for a 15 MV photon beam and field sizes of 1 x 1, 2 x 2, 5 x 5, and 10 x 10 cm 2 . Monte Carlo simulations were performed using the DOSRZnrc user code of EGSnrc. The experimental results agree with Monte Carlo simulations for all irradiation field sizes. Comparisons with Monte Carlo calculations show that the AAA algorithm provides the best simulations of PDD curves for all field sizes investigated. However, even this algorithm cannot accurately predict PDD values in the lung for field sizes of 1 x 1 and 2 x 2 cm 2 . An overdosage in the lung of about 40% and 20% is calculated by the AAA algorithm close to the interface soft tissue/lung for 1 x 1 and 2 x 2 cm 2 field sizes, respectively. It was demonstrated that differences of 100% between Monte Carlo results and the algorithms Batho, modified Batho, and equivalent TAR responses may exist inside the lung region for the 1 x 1 cm 2 field.
Journal of Applied Clinical Medical Physics 01/2010; 11(1):2947. · 0.96 Impact Factor
[show abstract][hide abstract] ABSTRACT: In the radiotherapy treatment planning of a lesion located in the head region with small field radiation beams, the heterogeneity corrections play an important role. In this work, we investigated the influence of a bony heterogeneity on dose profile inside a soft tissue phantom containing a bony material. PDD curves were obtained by simulation using the Monte Carlo code EGSnrc and employing Eclipse(R) treatment planning system algorithms (Batho, Modified Batho, Equivalent TAR and Anisotropic Analytic Algorithm) for a 15 MV photon beam and field sizes of 2x2 and 10x10 cm(2). The Equivalent TAR method exhibited better agreement with Monte Carlo simulations for the 2x2 cm(2) field size. The magnitude of the effect on PDD due to the bony heterogeneity for 1x1, 2x2 and 10x10 cm(2) field sizes increases to 10, 5 and 3%, respectively.
PLoS ONE 01/2010; 5(5):e10466. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this work we determined PDD curves and dose profiles for narrow beams produced by a cobalt-60 therapy unity aimed to be
used in radiosurgery through the cone beam technique. PDD curves were obtained by three techniques, namely diode dosimetry,
ionization chamber dosimetry and radiochromic film dosimetry. The results present a good agreement. The dose profiles obtained
for cobalt-60 were compared to those ones generated by a linac 2300C accelerator. For a same cone collimator, the area of
treatment generated by cobalt -60 beam was smaller. The mean responsible for this situation is the wider penumbra present
by the cobalt-60 beam.