25 research outputs found
Fricke and polymer gel 2D dosimetry validation using Monte Carlo simulation
Complexity in modern radiotherapy treatments demands advanced dosimetry systems for quality control. These systems must have several characteristics, such as high spatial resolution, tissue equivalence, three-dimensional resolution, and dose-integrating capabilities. In this scenario, gel dosimetry has proved to be a very promising option for quality assurance. In this study, the feasibility of Fricke and polymer gel dosimeters suitably shaped in form of thin layers and optically analyzed by visible light transmission imaging has been investigated for quality assurance in external radiotherapy. Dosimeter irradiation was carried out with a 6-MV photon beam (CLINAC 600C). The analysis of the irradiated dosimeters was done using two-dimensional optical transmission images. These dosimeters were compared with a treatment plan system using Monte Carlo simulations as a reference by means of a gamma test with parameters of 1 mm and 2%. Results show very good agreement between the different dosimetric systems: in the worst-case scenario, 98% of the analyzed points meet the test quality requirements. Therefore, gel dosimetry may be considered as a potential tool for the validation of other dosimetric systems.Fil: Vedelago, José Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba; ArgentinaFil: Chacón Obando, D.. Universidad Nacional. Physics Department; Costa Rica. Universidad Nacional de Córdoba; ArgentinaFil: Malano, Francisco Mauricio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba; ArgentinaFil: Conejeros, R.. Servicio de Radioterapia, Icos. Temuco, Chile;Fil: Figueroa, R.. Universidad de la Frontera; ChileFil: Garcia, D.. Servicio de Imagenes por Resonancia Magnética; ChileFil: González, G.. Servicio de Imagenes por Resonancia Magnética; ChileFil: Romero, Marcelo Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina. Universidad Nacional de Córdoba; ArgentinaFil: Santibañez, M.. Servicio de Imagenes por Resonancia Magnética; ChileFil: Strumia, Miriam Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Velásquez, J.. Servicio de Radioterapia; ChileFil: Mattea, Facundo. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Valente, M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad de La Frontera. Departamento de Ciencias Físicas; Chil
Ensayo Estructural No Destructivo Utilizando Microtomografía de Rayos X para Estimación de Diferencias de Densidad Másica en Muestras Óseas de Conejo
Al realizarse estudios sobre muestras óseas para analizar características como dureza, densidad y salud, se suelen utilizar equipamientos que permiten la cuantificación de la densidad electrónica, proporcional a la densidad másica, que se relaciona directamente con la densidad mineral ósea. El test conocido como densitometría ósea se suele realizar con equipos de rayos X, ultrasonido o por medio de la utilización de isótopos radioactivos. Este estudio cuantifica la cantidad mineral ósea por superficie y suele ser utilizado para evaluar, entre otros, riesgos de fracturas o estado de osteoporosis. La técnica de tomografía computada utiliza imágenes bidimensionales de rayos X y métodos de reconstrucción tomográfica implementados en algoritmos computacionales para obtener información de la estructura interna de un objeto, de forma no destructiva. Equipamientos especialmente desarrollados logran obtener imágenes con resolución sub-milimétrica, dando lugar a la técnica conocida como micro-tomografía. La posibilidad de estudiar estructuras óseas con este grado de resolución y obtener imágenes morfológicas tridimensionales con información de la densidad electrónica, presenta una importante opción para estudios específicos sobre, entre otros, crecimiento de hueso y estudios de nuevos componentes que permiten acelerar el crecimiento de tejidos dañados. En el presente trabajo se analizan muestras óseas del cráneo de conejos donde se han dañado determinadas zonas y se han injertado diferentes sustancias tendientes a evaluar respuestas de reparación de tejido óseo. El análisis se realiza a los fines de estudiar la performance de la técnica de micro-tomografía desarrollada en laboratorio con el objetivo de observar su potencialidad en este tipo de estudios y la capacidad de estos análisis en la caracterización de las propiedades físicas de este tipo de muestras.publishedVersionFil: Pérez, P. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.Fil: Pérez, P. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Instituto de Física Enrique Gaviola; Argentina.Fil: Malano, F. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.Fil: Malano, F. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Instituto de Física Enrique Gaviola; Argentina.Fil: Fernández Bodereau, E. Universidad Nacional de Córdoba, Facultad de Odontología; Argentina.Fil: Dedossi, G. Universidad Nacional de Córdoba, Facultad de Odontología; Argentina.Fil: Figueroa, R. Universidad de La Frontera. Temuco; Chile.Fil: Figueroa, R. Centro de Física e Ingeniería en Medicina. Universidad de La Frontera. Temuco; Chile.Fil: Santibañez, M. Universidad de La Frontera. Temuco; Chile.Fil: Santibañez, M. Centro de Física e Ingeniería en Medicina. Universidad de La Frontera. Temuco; Chile.Fil: Vedelago, J. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.Fil: Vedelago, J. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Instituto de Física Enrique Gaviola; Argentina.Fil: Vedelago, J. Universidad de La Frontera. Temuco; Chile.Fil: Vedelago, J. Centro de Física e Ingeniería en Medicina. Universidad de La Frontera. Temuco; Chile.Fil: Valente, M. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.Fil: Valente, M. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Instituto de Física Enrique Gaviola; Argentina.Fil: Valente, M. Universidad de La Frontera. Temuco; Chile.Fil: Valente, M. Centro de Física e Ingeniería en Medicina. Universidad de La Frontera. Temuco; Chile
Dosimetry of tumor targeting imaging by convergent X-ray beam as compared with nuclear medicine
During decades nuclear medicine procedures, based on radiolabeled agents, have proved to be efficient for diseases diagnosis and treatment. Radiation emerging from patient is detected aimed at localizing radiotracer distribution that is further correlated with biochemical/metabolic physiological processes. However, a significant drawback associated with current nuclear medicine procedures implementing radionuclide infusion regards to the inherent absorbed dose as well as radiopharmaceuticals' production, storage and elimination from patient body, thus representing a risk at patient and public health level. In the recent years, alternative methods have been proposed to reduce/eliminate radionuclides in some nuclear medicine procedures. The combination of high atomic number nanoparticles infused within patient body with incident X-ray beam, like tumor targeting and treatment, appears as a potential alternative method capable of theranostics. The process is based on inducing X-ray fluorescence and secondary electrons emission in high atomic number nanoparticles by means of excitation with an external X-ray beam, avoiding employing radioactive substances. The present work reports on the dosimetry performance of both methods, comparing whenever the external convergent X-ray beam alternative may involve less or larger radiation dose levels, according to comparable signal/image quality during the procedure. To this aim, a simplified theoretical model is proposed and associated Monte Carlo simulations are performed in order to compare typical case of nuclear medicine imaging with potential performance of an innovative method, called OXIRIS (Orthovoltage X-ray Induced Radiation and Integrated System), based on convergent X-ray beam exciting high atomic number nanoparticles infused in patient. The obtained results support the proposed alternative method's feasibility, once demonstrated that patient absorbed dose levels are relative similar to those currently used by nuclear medicine procedures, whereas dose to targeted region (tumor) are significantly higher, which may be useful for treatment purposes.Fil: Figueroa, R.. Universidad de La Frontera; ChileFil: Guarda, J.. Universidad de La Frontera; ChileFil: Leiva, J.. Universidad de La Frontera; ChileFil: Malano, F.. Universidad de La Frontera; ChileFil: Valente, Mauro Andres. Universidad de La Frontera; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin
Identification of storm surge vulnerable areas in the Philippines through the simulation of Typhoon Haiyan-induced storm surge levels over historical storm tracks
Super Typhoon Haiyan entered the Philippine Area of Responsibility
(PAR) on 7 November 2013, causing tremendous damage to infrastructure and
loss of lives mainly due to the storm surge and strong winds. Storm
surges up to a height of 7 m were reported in the hardest hit
areas. The threat imposed by this kind of natural calamity compelled
researchers of the Nationwide Operational Assessment of Hazards (Project
NOAH) which is the flagship disaster mitigation program of the Department of
Science and Technology (DOST) of the Philippine government to undertake a
study to determine the vulnerability of all Philippine coastal communities to storm surges of the same
magnitude as those generated by Haiyan. This study calculates the
maximum probable storm surge height for every coastal locality by
running simulations of Haiyan-type conditions but with tracks of
tropical cyclones that entered PAR from 1948–2013. One product of
this study is a list of the 30 most vulnerable coastal areas that can
be used as a basis for choosing priority sites for further studies to
implement appropriate site-specific solutions for flood risk
management. Another product is the storm tide inundation maps that the
local government units can use to develop a risk-sensitive land use
plan for identifying appropriate areas to build residential buildings,
evacuation sites, and other critical facilities and lifelines. The
maps can also be used to develop a disaster response plan and
evacuation scheme
Probabilistic storm surge inundation maps for Metro Manila based on Philippine public storm warning signals
A storm surge is the sudden rise of sea water over the astronomical tides, generated by an approaching
storm. This event poses a major
threat to the Philippine coastal areas, as manifested by Typhoon Haiyan on 8 November 2013.
This hydro-meteorological hazard is one of the main reasons
for the high number of casualties due to the typhoon, with 6300 deaths. It
became evident that the need to develop a storm surge inundation map is of
utmost importance. To develop these maps, the Nationwide Operational
Assessment of Hazards under the Department of Science and Technology (DOST-Project NOAH)
simulated historical tropical cyclones that entered the
Philippine Area of Responsibility. The Japan Meteorological Agency
storm surge model was used to simulate storm surge heights. The frequency
distribution of the maximum storm surge heights was calculated using
simulation results of tropical cyclones under a specific public storm warning
signal (PSWS) that passed through a particular coastal area. This determines
the storm surge height corresponding to a given probability of occurrence.
The storm surge heights from the model were added to the maximum astronomical
tide data from WXTide software. The team then created maps of inundation for
a specific PSWS using the probability of exceedance derived from the
frequency distribution. Buildings and other structures were assigned a
probability of exceedance depending on their occupancy category, i.e., 1%
probability of exceedance for critical facilities, 10% probability of
exceedance for special occupancy structures, and 25% for standard occupancy
and miscellaneous structures. The maps produced show the storm-surge-vulnerable areas in Metro Manila, illustrated by the flood depth of up
to 4 m and extent of up to 6.5 km from the coastline. This
information can help local government units in developing early
warning systems, disaster preparedness and mitigation plans, vulnerability
assessments, risk-sensitive land use plans, shoreline defense efforts, and
coastal protection measures. These maps can also determine the best areas to
build critical structures, or at least determine the level of protection of these
structures should they be built in hazard areas. Moreover, these will support
the local government units' mandate to raise public awareness, disseminate
information about storm surge hazards, and implement appropriate
countermeasures for a given PSWS