A matheuristic for the selection of beam directions and dose distribution in radiotherapy planning

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da contribuição do espalhamento nuclear não elástico de prótons na dose depositada em alvos com composição homogênea

Due the differences between interaction physics process with matter for protons and photons, the proton beam tomography (pCT) has some vantages to comparison with conventional tomography. Also it is confirmed that usually pCT has better dose distribution and highest contrast resolution. The pCT allow not only view the internal structure of an object without destroying it, but also directly measure of volume density of electrons. Also it is confirmed that usually pCT has better dose distribution and highest contrast resolution. At the same time, there are many scientific and technical aspects to a detailed study: the capacity and limitations of the pCT methods are not well clarified. Through computations, based on Monte Carlo Method was carried out a detailed study of the contribution of non-elastic nuclear spreading, and together was compared with an analytical model for the deflection angle and the lateral deflection of protons in the target volume. The programs used were SRIM 2006 code and MCNPX v.2.50 code

Análise de algoritmos computacionais utilizados em sistemas de planejamento de braquiterapia de alta taxa de dose: estudo comparativo com o Código MCNP-5C

In radiotherapy, computational systems are used for radiation dose determination in the treatment’s volume and radiometric parameters quality analysis of equipment and field irradiated. Due to the increasing technological advancement, several research has been performed in brachytherapy for different computational algorithms development which may be incorporated to treatment planning systems, providing greater accuracy and confidence in the dose calculation. Informatics and information technology fields undergo constant updating and refinement, allowing the use Monte Carlo Method to simulate brachytherapy source dose distribution. The methodology formalization employed to dosimetric analysis is based mainly in the American Association of Physicists in Medicine (AAPM) studies, by Task Group nº 43 (TG-43) and protocols aimed at dosimetry of these radiation sources types. This work aims to analyze the feasibility of using the MCNP-5C (Monte Carlo N-Particle) code to obtain radiometric parameters of brachytherapy sources and so to study the radiation dose variation in the treatment planning. Simulations were performed for the radiation dose variation in the source plan and determined the dosimetric parameters required by TG-43 formalism for the characterization of the two high dose rate iridium-192 sources. The calculated values were compared with the presents in the literature, which were obtained with different Monte Carlo simulations codes. The results showed excellent consistency with the compared codes, enhancing MCNP-5C code the capacity and viability in the sources dosimetry employed in HDR brachytherapy. The method employed may suggest a possible incorporation of this code in the treatment planning systems provided by manufactures together with the equipment, since besides reducing acquisition cost, it can also make the used computational routines more comprehensive, facilitating the brachytherapy ...

A complete dosimetric characterization of two Sr-90-Y-90 dermatologic applicators

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Two dimensional computer simulation of plasma immersion ion implantation

The biggest advantage of plasma immersion ion implantation (PIII) is the capability of treating objects with irregular geometry without complex manipulation of the target holder. The effectiveness of this approach relies on the uniformity of the incident ion dose. Unfortunately, perfect dose uniformity is usually difficult to achieve when treating samples of complex shape. The problems arise from the non-uniform plasma density and expansion of plasma sheath. A particle-in-cell computer simulation is used to study the time-dependent evolution of the plasma sheath surrounding two-dimensional objects during process of plasma immersion ion implantation. Before starting the implantation phase, steady-state nitrogen plasma is established inside the simulation volume by using ionization of gas precursor with primary electrons. The plasma self-consistently evolves to a non-uniform density distribution, which is used as initial density distribution for the implantation phase. As a result, we can obtain a more realistic description of the plasma sheath expansion and dynamics. Ion current density on the target, average impact energy, and trajectories of the implanted ions were calculated for three geometrical shapes. Large deviations from the uniform dose distribution have been observed for targets with irregular shapes. In addition, effect of secondary electron emission has been included in our simulation and no qualitative modifications to the sheath dynamics have been noticed. However, the energetic secondary electrons change drastically the plasma net balance and also pose significant X-ray hazard. Finally, an axial magnetic field has been added to the calculations and the possibility for magnetic insulation of secondary electrons has been proven.

Avaliação das condições de uso de um equipamento de tomografia computadorizada e otimização de protocolos de crânio empregados na rotina do HCFMB-UNESP

Almost forty years computed tomography (CT) has been one of the most powerful tools in diagnostic imaging. However, this modality delivers relatively high doses to their patients. It is known that the inappropriate use and unnecessary radiation may be associated with a significant risk of cancer, especially in pediatric patients. Moreover, the quality assurance in CT, provided and required by Portaria 453/98 and the guide of the RE 1016/05, ensures that the images generated by computer tomography provide reliable diagnostic information with doses as low as reasonably achievable. This research aimed to make the quality control (QC) of CT equipment; establish a better relationship between dose and noise on the image to protocols of skull CT according to the study of optimization proposed in 2005 by Daros; and assess the dose distribution in different cranial organs for protocols of adult and pediatric use in the routine of the Department of Diagnostic Imaging of HCFMB-UNESP. The equipment used for testing QC, optimization and dosimetry was a third generation tomograph GE Sytec 3000i

Análise quantitativa dos parâmetros físicos e radiométricos de procedimetnos radioterapicos em tumores de mama

The paper presents the radiometric parameters determined by the medical physicist during routine radiotherapy planning service in cases of breast cancer . The contours of the breast volume in patients undergoing radiation breast tumors at the Hospital das Clinicas, Faculty of Medicine , UNESP, Botucatu ( HCFMB ) during the year 2012 were analyzed . In order to analyze the influence of physical and radiometric parameters for the determination of the dose distribution of irradiated breast volume , four measurements of isodose curves were prepared in four different heights breast , and compared with the isodose curves plotted computationally . In the routine of planning , the medical physicist must determine the isodose curve that gives the best dose distribution homogeneity in the irradiated volume . The choice of the treatment plan can be done by dedicated computer systems , which require significantly costly investments available services having better financial support . In the Service of Medical Physics , Department of Radiotherapy , HC FMB , we use a two-dimensional software for determination of isodose curves , however , this software is out of date and frequently becomes inoperable due to the lack of maintenance and it is a closed system without feasibility of interference from computer professionals . This fact requires manual preparation of isodose curves , which are subject to uncertainties due to the subjectivity in the clinical interpretation of medical radiation oncologist and medical physicist responsible for planning , plus dispendiar significant calculation time . The choice of the optimal isodose curve depends on the energy of the radiation beam , the geometry and dimensions of the irradiated area . The contours of the breast studied in this work evaluations showed that , for a given energy input , such as the energy of 1.25 MeV of gamma radiation Unit Telecobaltoterapia , the determination of the percentage depth dose ( PDP ) ...

Braquiterapia com sementes de iodo-125: manufatura e tratamento

According to the National Institute of Cancer – INCA, 466.730 new cancer cases will occur in Brazil in 2009. Prostate and Lung cancer in man are the most incident types (in exception of the non-melanoma cancer). The brachytherapy with 125-iodine sources is an important method of prostate cancer treatment. The implant with iodine-125 seeds uses aproximately 100 seeds that are imported impossibilitating the treatment in large scale. For this reason, a multidisciplinary group was created at the Energetic and Nuclear Research Institute – Radiation Technology Center (IPEN –CTR / SP) to develop a national 125-iodine source and established a facility for local production. The seeds manufacture in Brazil will diminish the cost of treatment and prostate brachytherapy will be offered to more patients. This work aim is to observe and discuss the methods used in seeds manufacture there are being developed in Brazil and to present an prostate cancer case folloied in A.C. Camargo Hospital. The 125-iodine is adsorbed in an silver wire, then deposited at titanium coat. The weld is made by an process of plasm sealing. The seeds goes through several test to guarantee that there is no leakage. The result is an high quality and cheaper product. The implant tecnique is an fast and save procedure. The medical physicst preplan the case to stipulate the quantity of seeds there will be used. At the dat of the implant the medical physicst replan the procedure due to changes of volume in the organ. That assure the correct dose distribution in the target. Besides, the 125-iodine low energy is absorbed at the volume of interrest saving sourronding healthy tissues such as the rectum and the urethra

Análise da viabilidade de simulações com feixes de prótons de 100, 150, 200 e 250 MeV em alvos heterogêneos

In the recent years, the use of proton beams in radiotherapy has been an outstanding progress (SMITH, 2006). Up to now, computed tomography (CT) is a prerequisite for treatment planning in this kind of therapy because it provides the electron density distribution required for calculation of dose and the interval of doses. However, the use of CT images for proton treatment planning ignores fundamental differences in physical interaction processes between photons and protons and is, therefore, potentially inaccurate (SADROZINSKI, 2004). Proton CT (pCT) can in principle directly measure the density distribution needed in a patient for the dose distribution (SCHULTE, et al, 2004). One important problem that should be solved is the implementation of image reconstruction algorithms. In this sense, it is necessary to know how the presence of materials with different density and composition interfere in the energy deposition by ionization and coulomb excitation, during its trajectory. The study was conducted in two stages, was used in both the program SRIM (The Stopping and Range of Ions in Matter) to perform simulations of the interaction of proton beams with pencil beam type. In the first step we used the energies in the range of 100-250 MeV (ZIEGLER, 1999). The targets were set to 50 mm in length for the beam of 100 MeV, due to its interaction with the target, and short-range, and 70 mm for 150, 200 and 250 MeV The target was composed of liquid water and a layer of 6 mm cortical bone (ICRP). It were made 9 simulations varying the position of the heterogeneity of 5 mm. In the second step the energy of 250 MeV was taken out from the simulations, due to its greater energy and less interaction. The targets were diminished to 50 mm thick to standardize the simulations. The layer of bone was divided into two equal parts and both were put in the ends of the target... (Complete abstract click electronic access below)

Métodos de Calibração e Dosimetria de Aplicadores de Betaterapia

The sources of betatherapy for clinical use in Brazil are, the vast majority of strontium-90, radioactive element that is not produced in the country, and therefore requires importation of international laboratories accredited by the International Atomic Energy Agency (IAEA).The use of these resources is always limited the crediting of characteristic values supplied by the manufacturer tables that provide the nominal value of activity and dose distribution to determine the irradiation time of the injury. The Institute of Nuclear Energy Research (IPEN / CNEN-SP) has recently researching the emission profile of these types of radiation sources, and some jobs are being developed with ionization chambers extrapolation for the purpose of standardizing a systematic calibration sources betatherapy. Other studies using parallel measures dosimeters (TLD's) and simulations with the Monte Carlo method. Radiological films have also been used in studies of applicators dosimetric analysis of strontium-90. This paper seeks to analyze the different methods for calibration of applicators betatherapy, already consolidated in studies by examining the advantages and disadvantages of each procedure

Tissue distribution of a plasmid DNA encoding Hsp65 gene is dependent on the dose administered through intramuscular delivery

In order to assess a new strategy of DNA vaccine for a more complete understanding of its action in immune response, it is important to determine the in vivo biodistribution fate and antigen expression. In previous studies, our group focused on the prophylactic and therapeutic use of a plasmid DNA encoding the Mycobacterium leprae 65-kDa heat shock protein (Hsp65) and achieved an efficient immune response induction as well as protection against virulent M. tuberculosis challenge. In the present study, we examined in vivo tissue distribution of naked DNA-Hsp65 vaccine, the Hsp65 message, genome integration and methylation status of plasmid DNA. The DNA-Hsp65 was detectable in several tissue types, indicating that DNA-Hsp65 disseminates widely throughout the body. The biodistribution was dose-dependent. In contrast, RT-PCR detected the Hsp65 message for at least 15 days in muscle or liver tissue from immunized mice. We also analyzed the methylation status and integration of the injected plasmid DNA into the host cellular genome. The bacterial methylation pattern persisted for at least 6 months, indicating that the plasmid DNA-Hsp65 does not replicate in mammalian tissue, and Southern blot analysis showed that plasmid DNA was not integrated. These results have important implications for the use of DNA-Hsp65 vaccine in a clinical setting and open new perspectives for DNA vaccines and new considerations about the inoculation site and delivery system. © 2006 Coelho-Castelo et al; licensee BioMed Central Ltd.

The role of superstructure material on the stress distribution in mandibular full-arch implant-supported fixed dentures. A CT-based 3D-FEA

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Modelos de tratamento para adenocarcinomas de próstata tratados por radioterapia conformacional 3D

Radiotherapy is a branch of medical physics related to the treatment of malignant neoplasm, being an important instrument in the fight against cancer, when combined with the effort of a multidisciplinary team, composed of, physicians, physicists, nurses and technicians. Every year more than 3.5 million new cases of cancer are recorded in the world, being the prostate cancer responsible for approximately 25% of this amount (INCA and IARC, 2008). In this type of cancer, radiotherapy is a method indicated for treatement. The technological advance in this area over years has allowed a greater accuracy in the tumor location, more conformation of the radiation beam around the tumor, reducing the dose in healthy tissues and a consequent dose increase on treatment (Bedford et al., 1999). A radiotherapy planning, in which the physicist develops an important role, is composed of several steps, including choosing the best configuration of treatment beams. This choice has a close relationship with success of therapy and is critical to achieve the best distribution of dose inside the tumor and expose the least as possible the healthy tissue to radiation. In this work, two options for setting up camps in the first phase in a treatment of prostate cancer were simulated in computer planning: 4 fields orthogonal or “Box” with gantry angles in 00, 1800, 2700 e 90° and 4 fields angled or “X” (1350, 450, 3150 e 2250). The percentage of the rectal volume exposed to 40, 50, 60, 72 and 76 Gy should be limited to 60, 50, 25, 15 and 5% respectively (Greco et al., 2003). The femoral toxicity have limited dose by 70% of the total dose prescribed in a prostate treatment (Bedford et al., 1999). The planning of 27 patients with prostate adenocarcinoma submitted to 3D conformal radiotherapy were accompanied. As a result, it was assessed that the best TCP (tumor control probability)... (Complete abstract click electronic access below)

Biomass and minerals distribution in family of banana 'prata-ana' fertilized with zinc through thinned sprout

In the North of Minas Gerais it is cultivated basically 'Prata-Ana' banana, a cultivar that requires mainly Zn. The possibility of zinc supply, without this nutrient getting in contact with the soil, it is important for the region, since several factors take to the low availability of the element supplied by the soil, as: elevated organic matter content on the surface (from cultural residues); maintenance of high pH of the soil - above 6,00 - as strategy contrary to the proliferation of the causal agent of the Fusarium Wilt; frequent fertilizations with potassium and magnesium that, besides converting the medium into base, they reduce the participation of Zn in the balance cation/anion of the soil, hindering the absortion of this micronutrient by the plant. For determining the distribution of biomass and minerals in the Prata-Ana" banana, cultivated under irrigation in the North of Minas Gerais, when the zinc was supplied through thinned sprout, an experiment was carried out in the Irrigated Perimeter of Jaiba. The plants were fertilized with 0,00; 1,66 and 3,33 g.family-(1) of Zn, through thinned sprout. One month after the fertilizations from October 2007 and February 2008, the production of fresh mass (FM) and dry mass (DM) were evaluated, the contents and meanings of minerals in all the bananas "family" bodies composed by mother-plant with bunch + tall daughter-plant + granddaughter-plant. The doses of Zn did not influence on the production of FM and DM of the plants in the first evaluation, while in the second evaluation positive effect of the treatment was observed just for MF accumulated in the inferior leaves, in the portions of the medium third and inferior of the pseudostem, and in the mother-plant's rhizome. As much the content as the accumulation of nutrients in the mother-plants presented the following decreasing order: K > N > Ca > Mg > P > S > Fe > Zn > B > Cu. The Zn contents were affected by the dose of that micronutrient in the most of the studied situations. The zinc supplied through thinned sprout increased in the mother-plant, and then it was redistributed in the banana's "family".

Influence of Cusp Inclination on Stress Distribution in Implant-Supported Prostheses. A Three-Dimensional Finite Element Analysis

Purpose: The aim of this study was to assess the influence of cusp inclination on stress distribution in implant-supported prostheses by 3D finite element method.Materials and Methods: Three-dimensional models were created to simulate a mandibular bone section with an implant (3.75 mm diameter x 10 mm length) and crown by means of a 3D scanner and 3D CAD software. A screw-retained single crown was simulated using three cusp inclinations (10 degrees, 20 degrees, 30 degrees). The 3D models (model 10d, model 20d, and model 30d) were transferred to the finite element program NeiNastran 9.0 to generate a mesh and perform the stress analysis. An oblique load of 200 N was applied on the internal vestibular face of the metal ceramic crown.Results: The results were visualized by means of von Mises stress maps. Maximum stress concentration was located at the point of application. The implant showed higher stress values in model 30d (160.68 MPa). Cortical bone showed higher stress values in model 10d (28.23 MPa).Conclusion: Stresses on the implant and implant/abutment interface increased with increasing cusp inclination, and stresses on the cortical bone decreased with increasing cusp inclination.