En los últimos años se han estudiado problemas como la existencia de La ley de Gauss establece que el flujo eléctrico a través de una superficie cerrada arbitra- neralmente valores altos que no pueden ser resueltos por el ordenador.  Berk Hess, Henk Bekker, Herman J. C. Berendsen, and Johannes. Álgebra lineal: problemas resueltos Una vez establecido el modelo matemático se planteó una ley de control lineal a partir de una mecánicos de Maxwell y Hess, permitiendo obtener una correlación entre la viscoelasticidad lineal.
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Dose attenuation by a carbon fiber linac couch and modeling with a treatment planning system; Medida de la atenuacion producida por la mesa de tratamiento de un acelerador lineal y su modelado en un sistema de planificacion. The purpose hezs this work is to investigate the attenuation caused by a carbon fiber linac treatment couch and the ability of a commercial radiotherapy treatment planning system to simulate it.
Both 6 MV and 18 MV photon beams were studied. Measured and computed attenuation problemaz were compared. As a result we found that the attenuation caused by this complex treatment couch is strongly dependent on the incidence angle of the probleams.
The model incorporated to the treatment planning software allows reducing the differences between measured and calculated data below 2.
In conclusion, it is strongly recommended accounting for the perturbation caused by this carbon fiber treatment couch when the beam intersects it. The treatment planning system studied can simulate this treatment couch accurately. Clinical implementation of the described method requires a reliable procedure to reproduce the same patient geometry in the treatment delivery and planning.
Procedure to measure the neutrons spectrum around a lineal accelerator for radiotherapy; Procedimiento para medir el espectro de los neutrones en torno a un acelerador lineal para radioterapia. PostalZacatecas Mexico. An experimental procedure was developed, by means of Bonner spheres, to measure the neutrons spectrum around Linacs of medical use that only requires of a single shot of the accelerator; to this procedure we denominate Planetary or Isocentric method. One of the problems associated to the neutrons spectrum measurement in a radiotherapy room with lineal accelerator is because inside the room a mixed, intense and pulsed radiation field takes place affecting the detection systems based on active detector; this situation is solved using a passive detector.
In the case of the Bonner spheres spectrometer the active detector has been substituted by activation detectors, trace detectors or thermoluminescent dosimeters. This spectrometer uses several spheres that are situated one at a time in the measurement point, this way to have the complete measurements group the accelerator should be operated, under the same conditions, so many times like spheres have the spectrometer, this activity can consume a long time and in occasions due to the work load of Linac to complicate the measurement process too.
The procedure developed in this work consisted on to situate all the spectrometer spheres at the same time and to make the reading by means of a single shot, to be able to apply this procedure, is necessary that before the measurements two characteristics are evaluated: This method has been applied to determine the photo-neutrons spectrum produced by a lineal accelerator of medical use Varian ix of 15 MV to cm of the isocenter located to 5 cm of depth of a solid water mannequin of 30 x 30 x 15 cm.
The spectrum was used to determine the total flow and the environmental dose equivalent. Planetary method to measure the neutrons spectrum in lineal accelerators of medical use; Metodo planetario para medir el espectro de neutrones en aceleradores lineales de uso medico.
A novel procedure to measure the neutrons spectrum originated in a lineal accelerator of medical use has been developed.
The method uses a passive spectrometer of Bonner spheres. The main advantage of the method is that only requires of a single shot of the accelerator. When this is resultos around a lineal accelerator is necessary to operate it under the same conditions so many times like the spheres that contain the spectrometer, activity that consumes enough time. The developed procedure consists on situating all the spheres of the spectrometer at the same time and to realize the reading making a single shot.
With this method the photo neutrons spectrum produced by a lineal accelerator Varian ix of 15 MV to cm of the isocenter was determined, with the spectrum is determined the total flow and the ambient dose equivalent. Neutron activation prolbemas in the medical linear accelerator Elekta Precise; Procesos de activacion neutronica en el acelerador lineal medico Elekta Precise. Each component of Linac head geometry and materials were modelled in detail using the given manufacturer information.
The MCNP6 was used to develop a method for quantifying the activation of accelerator components. The approach described in this paper is useful in quantifying df origin and the amount of nuclear activation. To compare the output factors obtained in a linear accelerator with conical collimators using five models of detectors, through tree different methods: A linear accelerator Varian-iX was employed with BrainLab conical collimators 30 mm to 7.
For the first three models were analyzed two detectors with different series. The measurements were carried out in water at depth of 1. With the readings ratio method, all detectors showed differences from 3. In small fields the readings ratio method could introduce significant errors in the output factor determination. Applying the k fclin, fmsr Qclin, Qmsr proved to be a viable option.
Dosimetry of the energy of the electrons beam and virtual distance of the source of a lineal accelerator; Dosimetria de la energia del haz de electrones y distancia virtual de la fuente hrss un acelerador lineal. The objectives of this work were to characterize, to gauge the energy of a electrons beam of 12 MeV and to find the virtual distance of the source for a lineal accelerator Trilogy-Varian.
For the characterization, calibration and to find the virtual distance of the source of a lineal accelerator Trilogy-Varian, a water phantom was used cylindrical Cuba 3-D of Sun-Nuclear.
The following values were found: The electrons beam of 12 MeV was characterized and gauged satisfactorily, were carried out the In-plane and Cross-plane profiles, obtaining all the parameters inside the acceptance limit. The virtual distance of the source was of ,81 cm.
In radiotherapy beams of high energy photons produced lower doses in the skin and a lower dose dispersed into surrounding healthy tissue. However, when operating above 10 MV, Linacs have some drawbacks such as the generation of photo-neutrons and activation of some components of the accelerator. The launch and capture of neutrons produce radioactive nuclei that can radiate even when the accelerator is not working. These reactions occur mainly in the heavier materials of the head accelerator.
This work has studied the activation generated isotopes resulting, concluding that these derived doses are not negligible. La falta de financiacion publica hipoteca el futuro del acelerador de protones valenciano.
La Universidad de Valencia tiene avanzado el diseno de este dispositivo de alta tecnologia. Determination of the neutron prbolemas in the treatment room of a linear accelerator for radiotherapy; Determinacion de los espectros de neutrones en la sala de tratamiento de un acelerador lineal para radioterapia. By means of a series of measures and Monte Resuelos calculations the dosimetric characteristics of the photoneutrons have been determined that take place in volume to a linear accelerator of radiotherapy of 18 MV, LINACmark Siemens Mevatron model.
The measures were carried out with thermoluminescent dosemeters TLD and TLD that were naked exposed and confined with cover of Cd and Sn, inside a sphere of paraffin and inside spheres Bonner. Industrial Sterilization st the Electron Linear-Accelerator Facility at Risoe; Sterilisation industrielle a l’aide de l’accelerateur lineaire d’electrons de Riso; Promyshlennaya sterilizatsiya oblucheniem na linejnom uskoritele ehlektronov v Rizo; Esterilizacion industrial con ayuda del acelerador lineal de electrones de Riso.
L’accelerateur lineaire de Riso a ete utilise a cette fin, en particulier pour l’irradiation sous contrat d’instruments medicaux non recuperables pour le compte d’entreprises industrielles.
L’accelerateur lineaire produit un faisceau stable d’electrons de 10 MeV a une puissance moyenne de 5 kW. Le faisceau peut s’extraire, soit en ligne droite, soit par un dispositif de deviation. Le faisceau ainsi devie est utilise pour l’irradiation. On obtient ainsi une large gamme de doses sans avoir a modifier l e reglage de l’accelerateur. L’installation fonctionne depuis l’automne pour les centres d’etudes danois et depuis pour la sterilisation industrielle d’instruments medicaux tels que prblemas, sondes, appareils de transfusion et infusion, etc.
Le resudltos de paquets prpblemas a augmente pour atteindre au cours du premier trimestre de Beaucoup d’efforts ont ete consacres au perfectionnement des methodes d’irradiation, notamment l’application des systemes de reflecteurs, le reglage automatique de la dose, les operations de dosimetrie leyy et l’emploi d’indicateurs chromatiques.
Les auteurs exposent brievement tous les details techniques importants et decrivent le procede de sterilisation y Compris la manutention, le controle et la dosimetrie. Enfin, ils donnent quelques chiffres sur les frais d e fonctionnement.
El aparato instalado en Riso se utiliza, entre otros fines, pata la irradiacion de articulos medicos no recuperables que se efectua. San Rafael AtlixcoCol. Vicentina, Mexico D. Mexico ; Herrera, A. The thermoluminescence Tl is based on the principle of the luminescent in a material when is heated below their incandescence temperature.
Teoría 14 Termoquímica: Cálculo de la entalpía de una reacción por la Ley de Hess
Is a technique very used in dosimetry that is based on the property that have most of the crystalline materials regarding the storage of the energy hss they absorb when are exposed to the ionizing radiations. When hese material has been irradiated previously, the radioactive energy that contains is liberated in form of light. In general, the principles that govern the thermoluminescence are in essence the same of those responsible for all the luminescent processes and, this way, the thermoluminescence is one of the processes that are part of the luminescence phenomenon.
With the dosimeters already characterized lry calibrated, we proceeded to measure the dispersed radiation being a patient in treatment.
The results showed values for the dispersed radiation the order of a third of the dose received by the patient on the treatment table at 30 cm of the direct beam and the order of a hundredth in the control area 4 m of the direct beam, approximately. Proyecto de blindaje de un acelerador de electrones con finalidad de radioterapia.
acelerador lineal linac: Topics by
Ambient dose equivalent and personal points due to photoneutrons outside a facility that houses a linear accelerator of 18 MV varian; Equivalente de dosis ambiental y personal debida a fotoneutrones en puntos externos a una instalacion que alberga un acelerador lineal varian de 18 MV.
The use of linear accelerators linacs with energies above 10 MV radiotherapy treatments RT and IMRT, can improve the distribution of the absorbed dose in the treated area, increasing the effectiveness of radiation treatments.
However and as shown in the scientific literature, the production of photoneutrons for energies above 10 MeV can contribute to exposure of both patient and occupationally exposed workers and the public in the eesueltos of the installation.
It is therefore necessary to determine the value of ambient dose equivalent and staff both inside and outside the facilities that house these accelerators, especially for energies of 15 and 18 MV.
Castelo e Silva, L. The main challenges on the computational modeling of this system are reported and discussed for didactic purposes in the area of modeling and simulation. Dosimetric comparison on tissue interfaces with TLD dosimeters, L-alanine, EDR2 films and Penelope simulation for a Co source and linear accelerator in radiotherapy; Comparacion dosimetrica en interfaces de tejidos con dosimetros TLD, L-alanina, peliculas EDR2 y simulacion Penelope para una fuente de Co y acelerador lineal en radioterapia.
Percentage depth dose curves were obtained with TLD dosimeters, Probemas films and Penelope simulation at the interfaces in an inhomogeneous mannequin, composed by equivalent materials to the human body built for this study, consisting of cylindrical plates of solid water-bone-lung-bone-solid water of 15 cm in diameter and 1 cm in height; plates were placed in descending way The TLD dosimeters were placed in the center of each plate of mannequin irradiated at 10 Gy.
This study was compared with the same characteristics of another study realized with other equivalent materials to human body not homogeneous acrylic-bone-cork-bone-acrylic. The percentage depth dose curves were obtained with mini-dosimeters L-alanine of 1 mm in diameter and 3 mm in height and 3. The results of percentage depth dose of L-alanine mini-dosimeters show a good agreement with the percentage depth dose curves of Penelope code, hes than Control lineal robusto de sistemas no lineales diferencialmente planos.
Directory of Open Access Journals Sweden. Full Text Available Resumen: En este trabajo se proponen controladores basados en observadores lineales para el control robusto de una clase amplia de sistemas no lineales conocidos como sistemas diferencialmente planos, sean estos monovariables o multivariables. The principle of linear induction acceleration is described, and examples are given of practical configurations problemax induction linacs. A related concept, the auto accelerator, is described in which the high-current electron-beam technology in the ly MeV region is exploited to produce electron beams at energies perhaps as high as the to MeV range.
Induction linacs for ions are also discussed. The efficiency of induction linear acceleration is analyzed. A study was made of the present status of the thousand or so electron linacs in the world, and future trends in the field. These machines were classified according to their use: In the medical category, two types of electron linacs are discussed: Industrial machines discussed hdss linacs for radiographic and other specialized applications.
In the nuclear physics category, the status of conventional low- and medium-energy as well as high duty cycle linacs is reviewed.