ABSTRACT
Purpose: This report of a case of allergic contact hand dermatitis due to constituents of nitrile gloves is to bring to the attention of practitioners four important practice points: 1) allergic contact dermatitis may occur due to exposure to chemicals in nitrile gloves; 2) skin patch testing is used to identify the causative allergens; 3) targeted allergens may be necessary in addition to the baseline European standard series if the standard series is unhelpful; and 4) there are potential interventions to manage nitrile glove dermatitis. Findings: A laboratory analyst had occupational exposure to several allergens and had worn latex gloves. She was exposed to laboratory chemicals and powdered ore dust, containing precious metals. She developed hand dermatitis and was relocated to administrative duties not requiring glove use. Her dermatitis cleared but recurred when she returned to the laboratory and started using nitrile gloves. On history, nitrile gloves and platinum group metal ore dust were consistently associated with her hand dermatitis, but laboratory chemicals were not. Latex-specific immunoglobulin E (IgE) was negative, as were skin patch tests for 13 allergens in the metal series, including salts of platinum group metals. She had positive allergic reactions to cobalt chloride, formaldehyde, nickel sulphate, and quaternium 15 in the European standard series patch tests. She did not react to the rubber chemicals in the European standard series, including thiuram mix. The patient was then tested with the rubber additives series because of the glove-relatedness of her hand dermatitis. She had positive reactions to three thiuram compounds used as accelerators in rubber gloves. The patient went on vacation during which time her dermatitis improved. She was relocated to a position without glove use or ore contact and her dermatitis did not recur. Conclusions: An analytic laboratory worker developed hand allergic contact dermatitis due to nitrile glove constituents. The diagnosis is supported by the improvement in her dermatitis after cessation of glove use, negative metal series patch tests, and positive patch tests to accelerators found in rubber gloves. Nevertheless, a contribution to the dermatitis by metals in the platinum group metal ore dust cannot be excluded. Recommendations: Nitrile glove constituents should be considered in wearers who develop hand dermatitis. Skin patch testing is recommended to investigate putative agents. Specific patch test series for more targeted testing may be required
Subject(s)
Humans , Male , Female , Dermatitis , Gloves, ProtectiveABSTRACT
Introducción: La dupla Cyberknife y bisturí de rayos gamma (Infini) que se describe es la primera en Latinoamérica. Ambas máquinas han mostrado ser los mejores equipos para radiocirugía intracraneal. Se describe la experiencia inicial de Cyberknife en Centroamérica y su incorporación a un programa existente de bisturí de rayos gamma por vía de análisis comparativos dosimétricos. Material y método: En el año 2019 se realizaron planes comparativos y se trataron 180 pacientes con radiocirugía intracraneal con ambos sistemas tanto en patología tumoral, como vascular y funcional. Resultados: En el análisis dosimétrico comparativo en el gradiente de dosis de Infini mostró ser superior a Cyberknife en todos los casos. Para una esfera utilizando el colimador de 4 mm en Infini y de 5 mm en Cyberknife utilizando un plan isocéntrico con el -Trigeminal Path- el gradiente de dosis para Infini fue de 1.5 y para Cyberknife de 1.66. Para los casos de patología el gradiente de dosis media para Infini fue de 3 mm y para Cyberknife de 3.8 mm. Dando un puntaje de gradiente de dosis (Gradient Score Index) si Infini fuese de 100, Cyberknife obtuvo 87.3. Cyberknife mostró mejor conformalidad y cobertura (97% versus 96%) para todos los targets. Entre enero 2019 y enero 2020 se realizaron 180 radiocirugías, 60 con Cyberknife y 120 con Infini, 60 pacientes recibieron 146 sesiones con Cyberknife, radiocirugía fraccionada 39 (65%) y 21 (35%) en sesión única. Las dosis medias en tumores en dosis única fue 15 Gy (12.5 a 25 Gy) y en radiocirugía fraccionada 21 Gy (18 y 35). Ningún paciente ha experimentado toxicidad mayor a grado dos. Conclusiones: El bisturí de rayos gamma rotatorio reveló superioridad en gradiente de dosis con relación al Cyberknife. En su primer año Cyberknife ha mostrado ser una herramienta segura en el tratamiento de patología intracraneal. Más seguimiento clínico y radiológico es necesario para verificar su efectividad comparativa
Introduction: The match between Cyberknife and Infini here described in this article is the first in Latinamerica. Both machines have proven to be the best for intracranial radiosurgery, we describe our initial experience with Cyberknife in Central America and how it was incorporated in an existing gamma ray program by ways of dosimetry comparisons. Methods: During 2019 comparative plans were made and a total of 180 patients received intracranial radiosurgery with both technologies, patients were treated for tumors, vascular anomalies, and functional pathology. Results: Basic dosimetry analysis regarding dose gradient the Infini proved superior to Cyberknife in all plans. For a sphere using the 4 mm collimator in Infini and the 5 mm in Cyberknife along with an isocentric plan using the -Trigeminal Path- dose gradient was 1.5 for Infini and 1.66 for Cyberknife. For the pathology cases Infini was 3 mm and for Cyberknife 3.8 mm on mean. Giving a Gradient Score Index (GSI) if Infini would be 100, Cyberknife would be 87.3. Cyberknife showed better conformality and coverage for all pathology targets (97% versus 96%). From January 2019 to January 2020, 180 intracranial radiosurgeries were done, 60 with Cyberknife and 120 with Infini, 60 patients received 146 sessions with Cyberknife, fractionated scheme 39 (65%) and 21 (35%) single dose. The median dose for tumors was 15 Gy (12.5 a 25 Gy) for single session and 21 Gy (18 y 35) for fractionated scheme. No patient experienced a higher toxicity tan grade two. Conclusions: In its first year Cyberknife has shown to be safe in treating intracranial pathology. Infini had a better dose gradient than Cyberknife. Longer clinical and radiological follow-up is needed to verify its comparative effectiveness.
Subject(s)
Humans , Radiosurgery , Cerebrum , Neoplasm Metastasis , Neoplasms , NeurosurgeryABSTRACT
Introducción: Las recomendaciones en el manejo de metástasis superiores a 2 cm especialmente las sintomáticas sugieren cirugía como primera opción. En el presente artículo se discute el papel de radiocirugía como primer manejo de estos pacientes. Material y método: Se evaluaron 37 pacientes sintomáticos con lesiones metastásicas superiores a 8.5 cc tratados con radiocirugía entre el 2011 y el 2018. Resultados: La media de volumen fue de 12.5 cc (8.5-78.4), 9 (24%) pacientes fueron tratados utilizando LINAC, el volumen medio fue de 20 cc (9.2-70 cc). Los tratamientos con Gamma-Ray fueron administrados a 28 (76%) pacientes, 9 (32%) de ellos en protocolo de radiocirugía adaptativa, la dosis para todo el grupo fue de 13.8 Gy (7.5-18 Gy), con dosis media de 17.9 Gy, el volumen medio fue de 16.3 cc (8.5-78.4 cc) para gamma. El Karnofsky al inicio era de 60 (50-70) y de 80 (60-100) a los 30 días (P=0.0001). A los 30 días, 95% de las lesiones habían reducido su tamaño en un 74% (11-95%). La sobrevida media de la serie fue de 19 meses (4-34), el riesgo acumulado de muerte del SNC fue de 5.4%. Conclusiones: Radiocirugía en nuestra experiencia ha mostrado ser eficaz en el control de metástasis a cerebro de gran tamaño, reduciendo la necesidad de cirugí
Introduction: Current recommendations with regards to metastases larger than 2 cm specially in symptomatic patients suggest surgery as a first choice. We analyze the role of upfront radiosurgery as first line of treatment in such patients. Methods: 37 symptomatic patients that harbored tumors greater than 8.5 cc in volume were treated from 2011 to January 2018. Results: The median tumor volume was 12.5 cc (8.5-78.4), 9 (24%) patients were treated with LINAC with a volume of 20 cc (9.2-70 cc). The treatments with GammaRay were administrated to 28 (76%) patients, 9 (32%) of them with adaptive radiosurgery protocol, the prescription dose for the gamma group was 13.8 Gy (7.5-18Gy) mean dose of 17.9 Gy (13.2-23.3 Gy) with a mean volume of 16.3 cc (8.5-78.4 cc). Karnofsky score was 60 (50-70) the day of treatment and 80 (60-100) at 30 days (P=0.0001). At 30 days, 95% of the tumors had reduced in size in a 74% (11-95%) for those evaluated. Median survival was 19 months (4-34), with an accumulative risk of death from central nervous progression of 5.4%. Conclusions: Radiosurgery in our experience has shown to be effective in controlling large metastases, reducing the need for open surgery.
Subject(s)
Humans , Female , Breast Neoplasms , Central Nervous System , Radiosurgery , Cerebrum , Neoplasm Metastasis , Neoplasms , NeurosurgeryABSTRACT
Cancer therapy with accelerated proton or heavy ion beam is the most advanced radiotherapy technology, which is recognized by the international community at present. It is of great practical significance to study the medical proton and heavy ion accelerators and the radiotherapy technology, in order to promote the development of the advanced medical radiotherapy equipments and improve the quality of life of cancer patients in China. After a brief overview of cancer therapy with proton and heavy ion beam, this paper summarized and analyzed the application status of medical proton accelerators and medical heavy ion accelerators at home and abroad, and finally put forward the future development trends of medical proton and heavy ion accelerators and the radiotherapy technology, it can provide a reference for the progress and development strategies of the advanced radiotherapy equipments in China.
Subject(s)
Humans , China , Heavy Ions , Neoplasms , Therapeutics , Particle Accelerators , Proton Therapy , Protons , Quality of LifeABSTRACT
Abstract Heavy-ion induced two-neutron transfer reactions (18O,16O) at 84 MeV were studied on several targets up to high excitation energy of the residual nucleus thanks to the use of the MAGNEX magnetic spectrometer to detect the ejectiles. The obtained results indicate of the important role played by the nuclear paring.
Resumen Se estudiaron reacciones de transferencia de dos neutrones inducidas por iones pesados (18O, 16O) a 84 MeV en varios blancos hasta una alta energía de excitación del núcleo residual gracias al uso del espectrómetro magnético MAGNEX para detectar los residuos eyectados. Los resultados obtenidos indican el importante papel desempeñado por el apareamiento nuclear.
ABSTRACT
Summary SPES (Selective Production of Exotic Species) is the INFN project for a Nuclear Physics facility for the production of Radioactive Ion Beams (RIBs). It is in advanced construction in Legnaro, with several technological innovations and challenges foreseen, comprehensive of new achievements and improvements. SPES will provide mostly neutron-rich exotic beams, derived by the fission fragments (up to 1013fiss/s) produced in the interaction of an intense proton beam (200 μA) on a direct UCx target. Several other targets will be developed, in order to provide users a large beam selection. The expected SPES beam intensities, their quality and, finally, their maximum energies (up to 11 MeV/n for A=130) will permit to perform forefront research in nuclear structure and nuclear dynamics, studying a region of the nuclear chart far from stability. This goal will be reached by coordinating the developments on the accelerator complex and those of up-to-date experimental set-ups.
Resumen SPES (Selective Production of Exotic Species) es el proyecto INFN para una instalación de física nuclear para la producción de haces de iones radiactivos (RIB). Está en construcción avanzada en Legnaro, que prevé varias innovaciones tecnológicas y desafíos, con nuevos logros y mejoras. SPES proporcionará principalmente haces exóticos ricos en neutrones, derivados de los fragmentos de fisión (hasta 1013fisiones/s) producidos en la interacción de un intenso haz de protones (200 μA) con un blanco UCx directo. Se utilizarán diversos blancos para proporcionar a los usuarios una gran selección de haces. Las intensidades esperadas del haz SPES, su calidad y, finalmente, sus energías máximas (hasta 11 MeV/n para A=130) permitirán realizar investigaciones de vanguardia en la estructura nuclear y la dinámica nuclear, estudiando una región del mapa nuclear lejos de la estabilidad. Este objetivo se alcanzará coordinando los desarrollos en el complejo del acelerador con las configuraciones experimentales actualizadas.
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Objective To realize independent 3D dose calculation for intensity-modulated radiotherapy (IMRT) by building a two-source beam model of medical linear accelerator combined with a collapsed-cone convolution/superposition (CCCS) algorithm.Methods Two-source beam models of medical linear accelerators (Varian and Elekta) were built to calculate the 3D dose distributions using the CCCS algorithm.Scp,percent depth dose,and off-axis dose distribution were compared with the scanning data of ion chamber to confirm the calculation model.Twelve intensity-modulated treatment plans from each accelerator (a total of 24 plans) were selected for comparison.The calculation results of treatment planning system (TPS) were independently validated,and further compared with the measurement results of detector matrix.Results The dose deviations at the center of rectangle fields were lower than 1%,the deviation between doses at the same position in the field was not higher than 1%,and the positional deviation in the penumbra region was not higher than 1 mm.Gamma analysis based on 3%/3 mm standard was used to compare the results calculated by detectors and TPS.The pass rates were higher than 90%.Conclusions The independent 3D dose calculation for IMRT based on two-source beam model combined with CCCS algorithm has been successfully set up.The comparison between regular field and IMRT plan indicates that this method and calculation model can be used for independent 3D dose calculation of clinical plan.
ABSTRACT
Central neurocytoma (CN) typically presents as an intraventricular mass causing obstructive hydrocephalus. The first line of treatment is surgical resection with adjuvant conventional radiotherapy. Stereotactic radiosurgery (SRS) was proposed as an alternative therapy for CN because of its lower risk profile. The objective of this systematic analysis is to assess the efficacy of SRS for CN. A systematic analysis for CN treated with SRS was conducted in PubMed. Baseline patient characteristics and outcomes data were extracted. Heterogeneity and publication bias were also assessed. Univariate and multivariate linear regressions were used to test for correlations to the primary outcome: local control (LC). The estimated cumulative rate of LC was 92.2% (95% confidence interval: 86.5-95.7%, p<0.001). Mean follow-up time was 62.4 months (range 3-149 months). Heterogeneity and publication bias were insignificant. The univariate linear regression models for both mean tumor volume and mean dose were significantly correlated with improved LC (p<0.001). Our data suggests that SRS may be an effective and safe therapy for CN. However, the rarity of CN still limits the efficacy of a quantitative analysis. Future multi-institutional, randomized trials of CN patients should be considered to further elucidate this therapy.
Subject(s)
Humans , Brain Neoplasms , Follow-Up Studies , Hydrocephalus , Linear Models , Neurocytoma , Particle Accelerators , Population Characteristics , Publication Bias , Radiosurgery , Radiotherapy , Tumor BurdenABSTRACT
En el Departamento de Radioterapia del Instituto de Oncología y Radiobiología se ha puesto, en servicio clínico, un moderno acelerador lineal de electrones. Esto brindó la posibilidad de utilizar el dispositivo electrónico de imagen portal (EPID) para realizar los controles de calidad paciente-específico de tratamientos de radioterapia, con intensidad modulada (IMRT). Se estudió y validó el uso del EPID en la verificación de tratamientos de IMRT, modalidad de múltiples segmentos estáticos, con fotones de 6 MV de energía. Se determinó la curva dosis-respuesta del EPID para valores de dosis en agua. Se halló la profundidad de referencia en agua del EPID (Descripción: D:/Scielo/Nucleus html/n 59/img/e01055916.jpg) mediante la determinación de su respuesta a la variación del tamaño de campo, y la comparación de esta con la variación del factor de dispersión en agua, calculado para diferentes profundidades, con un sistema de planificación de tratamientos (TPS). Se calcularon perfiles y mapas de dosis a Descripción: D:/Scielo/Nucleus html/n 59/img/e01055916.jpg con el TPS, utilizando una configuración de haces colapsados. Los mapas de dosis y perfiles fueron comparados con los medidos, usando las imágenes procesadas del EPID para diferentes casos clínicos sencillos (campos abiertos y con cuña) y uno complejo (caso clínico de IMRT de cabeza y cuello). Se utilizó la función Gamma como herramienta de comparación. El criterio de comparación Gamma empleado fue 3 % de diferencia de dosis y 4 mm de distancia para la concordancia de la dosis. Se obtuvo una tasa de aceptación mayor del 90% para los puntos evaluados.
A modern clinical electron linear accelerator was commissioned at the Department of Radiotherapy in the Oncology and Radiobiology Institute. The use of electronic portal image device (EPID) for patient-specific intensity modulated radiotherapy (IMRT) quality assurance is assessed and validated. An IMRT step & shoot approach, using multileaf collimator was used. The EPID dose-response curve was determined for a 6MV photon beam. The EPID effective water scattering depth (Descripción: D:/Scielo/Nucleus html/n 59/img/e01055916.jpg) was assessed through measurements of its response versus field size variation and compared with the output factor scatter at different depths, calculated with a radiotherapy treatment planning system (TPS). Dose profiles and dose maps were calculated at Descripción: D:/Scielo/Nucleus html/n 59/img/e01055916.jpg with the TPS, using a collapsed beam setup. The dose maps and profiles were compared with the processed EPID images for simple cases (i.e. open and wedged fields) and a more complex case (a head and neck IMRT clinical case). Comparison was performed using the Gamma function. Results showed Gamma passing rates higher than 90 % for all compared points, using comparison criteria of dose difference 3% and 4mm of distance to agreement.
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Los análisis de riesgo aplicados a los tratamientos de radioterapia se han convertido en una necesidad innegable, partiendo de los peligros generados por la combinación del empleo de potentes campos de radiación sobre los pacientes y la ocurrencia de errores humanos y fallos de equipos durante esos tratamientos. La técnica por excelencia para llevar a cabo estos análisis ha sido la matriz de riesgo. El trabajo presenta el desarrollo de un nuevo algoritmo para ejecutar esta tarea con amplias potencialidades gráficas y analíticas, lo que lo convierte en una opción muy útil para el monitoreo del riesgo y la optimización de los programas de garantía de calidad. El sistema SECURE-MR, soporte informático de este algoritmo, se empleó con éxito en el análisis de riesgo de diversas prácticas de radioterapia. Lo distinguen nuevas posibilidades de análisis partiendo de la consideración de factores controladores del riesgo como las robusteces de frecuencia de iniciadores y de consecuencias. Sus capacidades analíticas y gráficas permiten novedosos desarrollos de ordenamiento de contribuyentes al riesgo y de representación de la información de procesos y secuencias accidentales. El trabajo muestra la aplicación del sistema propuesto a un proceso genérico de tratamiento de radioterapia con acelerador lineal.
Risk analyses applied to radiotherapy treatments have become an undeniable necessity, considering the dangers generated by the combination of using powerful radiation fields on patients and the occurrence of human errors and equipment failures during these treatments. The technique par excellence to execute these analyses has been the risk matrix. This paper presents the development of a new algorithm to execute the task with wide graphic and analytic potentialities, thus transforming it into a very useful option for risk monitoring and the optimization of quality assurance. The system SECURE-MR, which is the basic software of this algorithm, has been successfully used in risk analysis regarding different kinds of radiotherapies. Compared to previous methods, It offers new possibilities of analysis considering risk controlling factors as the robustness of reducers of initiators frequency and its consequences. Their analytic capacities and graphs allow novel developments to classify risk contributing factors, to represent information processes as well as accidental sequences. The paper shows the application of the proposed system to a generic process of radiotherapy treatment using a lineal accelerator.
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Simulation of a linear accelerator (linac) head requires determining the parameters that characterize the primary electron beam striking on the target which is a step that plays a vital role in the accuracy of Monte Carlo calculations. In this work, the commissioning of photon beams (6 MV and 15 MV) of an Elekta Precise accelerator, using the Monte Carlo code EGSnrc, was performed. The influence of the primary electron beam characteristics on the absorbed dose distribution for two photon qualities was studied. Using different combinations of mean energy and radial FWHM of the primary electron beam, deposited doses were calculated in a water phantom, for different field sizes. Based on the deposited dose in the phantom, depth dose curves and lateral dose profiles were constructed and compared with experimental values measured in an arrangement similar to the simulation. Taking into account the main differences between calculations and measurements, an acceptability criteria based on confidence limits was implemented. As expected, the lateral dose profiles for small field sizes were strongly infl uenced by the radial distribution (FWHM). The combinations of energy/FWHM that best reproduced the experimental results were used to generate the phase spaces, in order to obtain a model with the motorized wedge included and to calculate output factors. A good agreement was obtained between simulations and measurements for a wide range of fi eld sizes , being all the results found within the range of tolerance.
La simulación del cabezal de un acelerador lineal requiere de la determinación de los parámetros que caracterizan el haz primario de electrones que incide en el blanco de radiación, los cuales juegan un papel importante en la exactitud de los cálculos con Monte Carlo. En este trabajo se realizó la habilitación de los haces de fotones (6 MV y 15 MV) de un acelerador Elekta Precise, empleando el código de Monte Carlo EGSnrc. De forma adicional se estudió la influencia que ejerce cambios en las características del haz primario de electrones sobre la distribución de dosis absorbida en diferentes campos de radiación. Basado en la dosis absorbida, curvas de dosis en profundidad y perfiles de dosis se calcularon y compararon con valores experimentales medidos en un arreglo similar a las simulaciones empleando criterios de aceptabilidad. Los perfiles de dosis para campos pequeños resultaron ser fuertemente dependientes de la distribución radial (FWHM). Las combinaciones de energías/FWHM que mejor se ajustaron a las mediciones se emplearon en la generación de espacios de fases, para obtener un modelo con la cuña motorizada y para el cálculo de los factores de campo. Se obtuvo muy buena correspondencia entre las mediciones y las simulaciones realizadas, encontrándose todos los resultados dentro de los márgenes de tolerancias.
ABSTRACT
The analysis of some parameters of interest in radiotherapy Medical Physics based on an experimentally validated Monte Carlo model of an Elekta Precise lineal accelerator was performed for 6 and 15 MV photon beams. The simulations were performed using the EGSnrc code. As reference for simulations, the values of the previously obtained optimal beam parameters (energy and FWHM) were used. Deposited dose calculations in water phantoms were done, on typical complex geometries commonly are used in acceptance and quality control tests, such as irregular and asymmetric fields. Parameters such as MLC scatter, maximum opening or closing position, and the separation between them were analyzed from calculations in water. Similarly simulations were performed on phantoms obtained from CT studies of real patients, making comparisons of the dose distribution calculated with EGSnrc and the dose distribution obtained from the computerized treatment planning systems used in routine clinical plans. All the results showed a great agreement with measurements, fi nding all of them within tolerance limits. These results allowed the possibility of using the developed model as a robust verifi cation tool for validating calculations in very complex situations, where the accuracy of the available TPS could be questionable.
El análisis de algunos parámetros de interés en la física médica de la radioterapia, basado en un modelo de Monte Carlo de un acelerador Elekta Precise, fue realizado en este trabajo para los haces de fotones de 6 y 15 MV. Las simulaciones se realizaron con el código EGSnrc. Como referencia para las simulaciones, se emplearon los parámetros óptimos (energía y FWHM) previamente calculados. Los cálculos de la dosis absorbida se realizaron con maniquíes de agua sobre geometrías complejas, comúnmente empleadas en las pruebas de aceptación y control de calidad en la clínica. Parámetros de interés como la dispersión en las MLC, máxima posición de apertura o cierre y la separación entre estas se analizaron a partir de los cálculos en agua. De forma similar se realizaron cálculos en maniquíes construidos a partir de los estudios tomográficos, y comparaciones con los resultados reportados por el sistema de planifi cación en dichos casos. Los resultados obtenidos evidenciaron una gran concordancia con las mediciones, encontrándose dentro de los límites de tolerancias reportados. Estos resultados crean la base para el empleo del modelo de Monte Carlo como una herramienta robusta para la verificación y validación de los cálculos de dosis en situaciones de gran complejidad, donde la exactitud de los sistemas de planificación es cuestionable.
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Los aceleradores y los detectores utilizados en las investigaciones en física de partículas sirven y han servido desde hace más de 100 años para la detección y cura de enfermedades. Gracias a los avances en la física experimental de partículas, se han desarrollado a lo largo de los años aceleradores más potentes y sistemas de detección más precisos y sofisticados. Estos, conjuntamente con los modernos sistemas de cómputo, han permitido aplicaciones hasta hace poco tiempo impensadas en la medicina. En este trabajo se esboza la historia de estos instrumentos, sus principios de funcionamiento y sus ventajas en las aplicaciones médicas, especialmente en el campo de la detección y tratamiento de tumores.
Accelerators and detectors used in particle physics research have been used for more than 100 years for detection and cure of diseases. Thanks to the progress in experimental particle physics, more powerful accelerators and more precise and sophisticated systems have been developed. These, together with modern computation systems have enabled applications in medicine not even thought of until recently. This work outlines the history of these instruments, their working principles and advantages for health applications, especially in the field of tumor detection and treatment.
Os aceleradores e os detectores utilizados nas pesquisas em física de partículas servem e têm servido já faz mais de 100 anos para a detecção e cura de doenças. Devido aos avanços na física experimental de partículas, aceleradores mais potentes e sistemas de detecção mais precisos e sofisticados têm sido desenvolvidos ao longo dos anos. Eles, junto com os modernos sistemas de cômputo, permitiram aplicações até pouco tempo atrás impensadas em medicina. Neste trabalho esboçamos a história destes instrumentos, seus princípios de funcionamento e suas vantagens nas aplicações médicas, especialmente no campo da detecção e tratamento de tumores.
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Objective To study the spectrum structure of X-ray and simplify the description method of it. Methods By the general program of Monte Carlo Geant4 to study X-ray spectrum structure and angular distribution of X-ray energy spectrum. Results The results of percentage depth doses and profile curves at different depths of any radiation fields in water phantom calculated by Monte Carlo Geant4 were consistent with the measurements. Conclusions In radiotherapy, X-ray with same nominal energy have very similar dosimetry characteristics, this indicates they have very similar energy spectrum and angular distribution of spectrum. the differences of dosimetric details reflect the different details of the X-ray spectrum structure and angular distribution of X-ray energy spectrum. These studies have very important significances to rapidly build precise virtual source modeling for Monte Carlo calculation based on dose curves measurements in water phantom.