Uso do método de Monte Carlo para simulação e detecção do espectro de raios-X gerado com feixes de elétrons em alvo de Molibdênio, utilizando o Geant4

The huge demand for procedures involving ionizing radiation promotes the need for safe methods of experimentation considering the danger of their biological e ects with consequent risk to humans. Brazilian's legislation prohibits experiments involving this type of radiation in humans through Decree 453 of Ministry of Health with determines that such procedures comply with the principles of justi cation, optimization and dose limitation. In this line, concurrently with the advancement of available computer processing power, computing simulations have become relevant in those situations where experimental procedures are too cost or impractical. The Monte Carlo method, created along the Manhattan Project duringWorldWar II, is a powerful strategy to simulations in computational physics. In medical physics, this technique has been extensively used with applications in diagnostics and cancer treatment. The objective of this work is to simulate the production and detection of X-rays for the energy range of diagnostic radiology, for molybdenum target, using the Geant4 toolkit. X-ray tubes with this kind of target material are used in diagnostic radiology, speci cally in mammography, one of the most used techniques for screening of breast cancer in women. During the simulations, we used di erent models for bremsstrahlung available in physical models for low energy, in situations already covered by the literature in earlier versions of Geant4. Our results show that although the physical situations seems qualitatively adequate, quantitative comparisons to available analytical data shows aws in the code of Geant4 Low Energy source

Controle de Qualidade em Raios X Odontológico Periapical

The purpose of this work is to provide quality control requirements and security in dental x-rays in order to obtain good quality image which allows the correct diagnosis, which reduces the dose to the patient, mainly due to the repetition of tests, and decreasing cost. The requirements apply to related activities to quality control and procedures using ionizing radiation for diagnostic imaging in dentistry by evaluating a minimum set of parameters to be tested or verified. Quality control follows the Ordinance No. 453 of the Ministry of Health of 06.01.1998, SS Resolution No. 625 of 12.14.1994 and Resolution No. 64 of the Health Surveillance Center – Department of Health of Sao Paulo and National Health Surveillance Agency – Ministry of Health of Brazil. This study was conducted in the city of Marilia, Sao Paulo, along with the Company P&R Consulting and Medical Physics, in a dental clinic of the University UNIMAR in the x-ray equipment used on that site. The physical parameters of the device were tested with the aid of ionization chambers to measure rates of radiation, electrometer to measure rates of time, kV and doses, radiographic films and positioning devices. Finally, this work demonstrates the need and importance of quality control, which one ensures the proper use of x-ray machines, maintaining efficiency and at the same time it reduces the risks to the patient, to the dentist and to the general public

Distribuição e dispersão dos níveis radiométricos do setor técnico de medicina nuclear do hospital das clínicas da faculdade de medicina de botucatu

Nuclear medicine uses non-sealed sources for exams and treatments, because the movement of these sources, source of patients injected or not, involve a wide range of environmental radiometric levels. To better control of these levels this study was aimed at monitoring points strategically distributed in all environments Sector Technical Nuclear Medicine, Hospital of the Botucatu Medical School, performing two measurements at random times daily for a period of three months, sampling the normal routine of the sector. The detector Geiger-Muller was used for the acquisition of exposure rates of the points, efficiency and reprodutibility test have shown good performance of this equipment for this purpose. The results allowed to make a projection of annual dose for each environment indicating higher risks for Occupationally Exposed Individuals as well as Public Individuals compared with the limits established by the National Commission of Nuclear Energy. Was developed a spatial map of dose that can be used as a visual warning to the regions with the highest exposure to ionizing radiation, enabling reduced risk of a potential exposure

Avaliação do efeito da gastrectomia na motilidade e no esvaziamento gástrico em ratos por biosusceptometria de corrente alternada

The study of gastrointestinal tract (GIT) functions is necessary due to the increasing number of pathologies associated with it. Directly influencing the quality of life, the gastrointestinal tract provides a number of parameters that, when analyzed, allow us to describe its dysfunctions. Thus, many techniques can be combined to obtain these properties related to the GIT. However, these techniques are often invasive, require surgery, catheter insertion, or to build a temporal model of these functions, require the sacrifice of animals in a series of data collection. The technique used in this study has the advantage of having a low operating cost, being free of ionizing radiation, non-invasive and is known as biosusceptometry AC (BAC), used to evaluate the properties of the GI tract by monitoring the position and concentration of materials magnetically marked. The sensor consists of two pairs of coils, one reference and one for detection. A fixed base line separates the sensing and reference coils, and also functions as support for the instrumentation. It is also important to note that the detection coils are arranged in a first order (subtraction) gradiometric way. The objective of this study was to analyze the effects of gastrectomy in gastric emptying and gastrointestinal transit time of solid food in rats using a BAC system associated with magnetic markers. To realize this study was constructed a dedicated BAC sensor, built to analyze these GIT properties. Data acquisition was obtained by aligning the magnetic sensor with the stomach and colon of the animal at pre-determined intervals. Thus, when approaching the magnetic material of the sensor, the balance created between the two sides of the sensor is broken. This imbalance can be measured, digitized and acquired. Tracer was used as a ration magnetically marked with ferrite... (Complete abstract click electronic access below)

Estudo da técnica de ressonância magnética para algumas aplicações voltadas à neurologia e à neurociência

Magnetic resonance imaging (MRI), which is studied since 1938, is a technique used in medicine to produce high quality images from inside the human body. These images are produced non-invasively and without ionizing radiation. In addition, MRI is an extremely flexible technique, with which it is possible to produce images with different contrasts that provide different information about the anatomy, structure and function of the human body, and it is therefore one of the techniques preferred by radiologists. The phenomenon of MRI is based on the interaction of magnetic fields with the nuclear spins of the scanned sample. In this work a detailed study of the technique of magnetic resonance imaging is presented, with a description of the main features of the images produced by the technique and an analysis of its application to the fields of applications Neurology and Neuroscience

Controle de qualidade e levantamento radiométrico em aparelho de Raios-X médico convencional

Along with the advance of technology, in terms of the expansion of medical exams that uses the ionizing radiation for diagnosis, there is also the concern about quality control for maintaining quality in radiographic imaging and for delivering low dose to the patient. Based on the Federal Order 453 of the Secretariat of Health Surveillance, which takes account of the practical and justification of individual medical exposures, the optimization of radiological protection, limitation of individual dose, and the prevention of accidents, were done through this paper radiodiagnostic tests on medical equipment in order to accept it or not, according to SVS-453. Along with the help and support of P&R Consulting and Medical Physics Marilia, SP, were made Quality Control and Radiometric Control in equipment from various cities across the state of São Paulo. The equipment discussed in this work is classified as conventional X-ray. According to the Federal Order SVS-453, the quality control in the program of quality assurance should include the following minimum set of constancy tests, with following minimum frequency: biennial tests for representative values of dose given to the patients of radiography and CT performed in the service; annual tests for accuracy of the indicator tube voltage (kVp), accuracy of exposure time, half-value layer, aligning the central axis of the beam of x-ray tube, performance (mGy / mA.min.m²), linearity of the rate of kerma on air with the mAs, reproducibility of the kerma on air rates, reproducibility of the automatic exposure, focal spot size, integrity of accessories and clothing for individual protection; semiannually for collimation system accuracy; weekly for temperature processing system and sensitometry processing system. For the room Radiometric Survey it was done a sketch...(Complete abstract click electronic access below)

Aplicações práticas de proteção radiológica nas áreas de medicina nuclear e radiodiagnóstico em instalações hospitalares

After the discovery of ionizing radiation, its applications in various fields of science began to take significant proportions. In the case of medicine, there are the application areas in radiotherapy, diagnostic radiology and nuclear medicine. It was then necessary to create the field of radiological protection to establish the conditions necessary for the safe use of such ionizing radiation. Apply knowledge obtained during the graduation stage and in the practice of radiological protection in the areas of nuclear medicine and diagnostic radiology. In the area of nuclear medicine, tests were made in the Geiger-Muller counters (GM) and the dose calibrator (curiometer), the monitoring tests of radiation, waste management, clean of the Therapeutic room and testing the quality control of gamma-chambers. In the area of radiology, were performed tests of quality control equipment for conventional X-ray equipment and x-ray fluoroscopy, all following the rules of the National Health Surveillance Agency (ANVISA), and reporting of tests. The routine developed in the fields of nuclear medicine in hospitals has proved very useful, since the quality control of GM counters contribute to the values of possible contamination are more reliable. The control of dose calibrator enables the patient not to receive different doses of the recommended amounts, which prevents the repetition of tests and unnecessary exposure to radiation. The management of waste following the rules and laws established and required for its management. Tests for quality control of gamma chambers help to evaluate its medical performance through image. In part of diagnostic radiology, tests for quality control are performed in order to verify that the equipment is acceptable for usage or if repairs are needed. The knowledge acquired at the internship consolidated the learning of graduation course

Avaliação da Taxa de Exposição em Exames Radiológicos Realizados em Procedimentos Cirúrgicos - Minimização dos Riscos em Indivíduos Ocupacionalmente Expostos

This paper consists in the evaluation of the exposure rate to ionizing radiation to which professionals working in surgical procedures which require radiological examinations are subjected. Were initially performed real-time readings of exposure rate within four distinct operating rooms during the execution of four surgical procedures that made use of fluoroscopy equipment (including three orthopedic surgeries, one in the shoulder, one in the arm, another for deployment of metal pin in the leg region, and a fourth for vascular procedure); in these surgeries were used ionization chamber detector and an electrometer. In order to check the values achieved, was made a re-evaluation of the distribution of the rate of exposure to radiation, from the surgical procedures, now with thermoluminescent dosimeters (TLDs). For this, thirty TLDs were distributed in the operating rooms, arranged in points of interest as occupation by professionals. The TLDs were prepared for thirty consecutive days, after which they were removed and replaced with new dosimeters not exposed yet. The dosimeters were subjected to reading of the rate of exposure; this procedure was repeated for four months without interruption. The quantification of the results sought primarily to convert the rate of exposure for equivalent dose rate, both in measurements with ionization chamber as in measurements with TLDs, in order to highlight the presence of the biological effect of ionizing radiation for comparisons within scientific context. Then, the results were plotted to establish the relationship between the values of equivalent dose and the distance to the central axis of the x -ray source, confirming the inverse square law for distance. Finally, the values were associated with the maximum limit recommended by the legislation for occupationally exposed individuals. The methodology for the analysis and quantification of the data in this work aims at implementing a work plan that meets ...

Tomografia por biosusceptometria de corrente alternada

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Alterações epigenéticas e do número de cópias do gene SFN em carcinomas mamários

Pós-graduação em Ciências Biológicas (Genética) - IBB

Mapeamento do nível radiométrico e construção de mapa espacial em serviço de medicina nuclear

Nuclear Medicine is a medical modality of therapy and diagnostic imaging using unsealed radioactive sources for its purposes. This routine activity promotes the transit of radioactive sources for the area of installation, beyond the transit of patients injected with radioisotope, which also contribute to raising the radiometric level of environment. As a consequence, it has exposured workers and public individuals to the ionizing radiation. There are protective mechanisms of radiation exposure, personal protective equipments, and measurement planes established in standard measurement at certain points of the environment in order to identify any increase in radiometric levels and \ or contamination, but do not cover the entire space occupied by workers and patients. To accomplish with the individual dose limits established by the National Commission of Nuclear Energy, it is interesting if there is an individualized classification for each Nuclear Medicine service. This work aimed to promote an analysis of the radiometric level distribution across the extent of the Technical Nuclear Medicine Sector of Hospital of the Botucatu Medical School, and produce a spatial map to identify locations with higher exposure rate to the ionizing radiation, can be used as a risk map to assist the Occupationally Exposed Individuals (IOE). To perform the radiometric levels checking it was used a digital Geiger-Muller detector available in the sector, due to its practicality compared to other detectors. Measurements were carried out at four different times for all days of the week, at points strategically established to cover all the installation

Complexos heterobilantanídicos luminescentes sob excitação UV e raios X

Pós-graduação em Química - IQ

Investigação do papel de HJURP (Holliday Junction Recognizing Protein) na resistência de células de glioblastoma multiforme à radiação ionizante

Pós-graduação em Biociências e Biotecnologia Aplicadas à Farmácia - FCFAR

New insights into the structural characteristics of irradiated crotamine

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Relationship between head and neck cancer therapy and some genetic endpoints

Head and neck cancer (HNC) is the sixth most common human malignancy worldwide. The main forms of treatment for HNC are surgery, radiotherapy (RT) and chemotherapy (CT). However, the choice of therapy depends on the tumor staging and approaches, which are aimed at organ preservation. Because of systemic RT and CT genotoxicity, one of the important side effects is a secondary cancer that can result from the activity of radiation and antineoplastic drugs on healthy cells. Ionizing radiation can affect the DNA, causing single and double-strand breaks, DNA-protein crosslinks and oxidative damage. The severity of radiotoxicity can be directly associated with the radiation dosimetry and the dose-volume differences. Regarding CT, cisplatin is still the standard protocol for the treatment of squamous cell carcinoma, the most common cancer located in the oral cavity. However, simultaneous treatment with cisplatin, bleomycin and 5-fluorouracil or treatment with paclitaxel and cisplatin are also used. These drugs can interact with the DNA, causing DNA crosslinks, double and single-strand breaks and changes in gene expression. Currently, the late effects of therapy have become a recurring problem, mainly due to the increased survival of HNC patients. Herein, we present an update of the systemic activity of RT and CT for HNC, with a focus on their toxicogenetic and toxicogenomic effects.