calibración de Unidades hounsfield en términos de números atómicos efectivos y densidades electrónicas usando CT de energía dual

El cálculo de dosis con algoritmos Monte Carlo (MC) utiliza imágenes de CT del paciente. A partir de las Unidades Hounsfield (HU) es posible obtener información sobre la densidad electrónica (ρe) y composición elemental de cada tejido. Un cálculo preciso de dosis y una adecuada corrección por inhomogeneidades es parcialmente determinada por la precisión de la calibración de las HU en términos de estos parámetros. En este trabajo se presentan resultados de calibración de HU en términos de números atómicos efectivos (Zeff) y ρe relativas utilizando un maniquí con insertos tejido-equivalente y estudios de tomografía computarizada (CT) de energía dual

An investigation of the imaging performance of new digital x-ray detectors

Recent advances in detector technology have made possible to develop imaging detectors with enhanced x-ray response and fast readout electronics. In this project a quantitative evaluation of the imaging performance of two of these new x-ray detectors has been made and their possible application in the field of medical imaging has been studied. The systems investigated are based on position sensitive detectors, and produce digital output in real time. Gaseous and semiconductor detectors that use different modes of x-ray detection (counting mode and integrating mode) and different irradiation geometries (scanned projection and area projection) were considered. An experimental procedure for the assessment of the imaging characteristics of digital x-ray detectors was set up. The evaluation process was based on widely accepted image assessment and dosimetry techniques. It included both subjective and objective measurements of image quality, and took into account the effect that various digital parameters - such as sampling aperture, sampling distance and quantization - have in the imaging characteristics of the digital radiography system. Subjective measurements were based on phantom studies, and consisted in the determination of the threshold-contrast detail-detectability properties of the imaging systems under investigation at different exposure levels. Objective measurements included the study of spatial transfer characteristics and resolution using modulation transfer function analysis, and of system noise characteristics such as noise power spectrum and detective quantum efficiency. The results of the experimental measurements have been compared with equivalent figures of system performance obtained with conventional film-screen combinations. Computer models were used to investigate the parameters that alter the performance of the detectors, and to study the effect that exposure conditions (e.g. filtration and kVp) and photon statistics have upon image quality

Using cosmic rays for the study of the pyramid of the sun at Teotihuacan

TrayectosConjuntando la fisica y la arqueología se formó un proyecto de investigación de interés para ambas disciplinas que además acrecienta la riqueza cultural de México. Usando muones, que son partículas provenientes de la alta atmósfera, se efectuará una introspección de la Pirámide del Sol de Teotihuacan para conocer su interior sin tocarlaWe present a join research project of physics and anthropology of great value for the Mexican heritage. Using muons, cosmic particles from the upper atmosphere, introspection is made of the Sun Pyramid without touching it

HAWC: un nuevo observatorio de rayos gamma en México

Tema del mesLa astrofísica de rayos gamma de muy alta energía es un área de investigación nueva en la ciencia, que nos abre una ventana para observar un universo violento, energético, extremo y transitorio. En México, esta área se está desarrollando alrededor del observatorio HAWC, un proyecto bi-nacional entre Estados Unidos de Norte América y México. HAWC es un observatorio de frontera de rayos gamma que está siendo construido en el Volcán Sierra Negra, Puebla, a 4 100m de altitud. Entre otras de las características que lo hacen único en el mundo, están su diseño, que no incluye ni antenas ni espejos, sino técnicas de detección de partículas de alta energía; su capacidad de operación durante las 24 horas del día, y su campo de visión de casi 70 grados. Desde la elección del sitio de HAWC en México en 2007, científicos de diferentes áreas como geofísica, física de rayos cósmicos, física de altas energías y astronomía, han trabajado conjuntamente en su desarrollo, instalando un primer prototipo que ya está en operación. En este artículo se presenta a HAWC, su diseño y caso científico, así como los avances y estado de construcciónThe very high-energy gamma ray astrophysics is a new research area in science that opens up a window to observe a violent, highly energetic and transitory universe. In México, it is developing around the HAWC observatory, a bi national project between United States and México. HAWC is a ground based gamma ray observatory of international level that is being built in the Volcano Sierra Negra at 4100 m altitude. Other characteristics that make it unique are its design that does not include mirrors or antennas but techniques of high energy particle detection, its 24 hours of duty cycle and its almost 70 degrees of field of view. Since the site selection of HAWC in 2007, scientist of different areas such as geophysics, cosmic rays, high energy and astronomy, have been working together in the construction of HAWC, installing a first prototype that is now operational. In this article, HAWC, its design and scientific case are presented as well as the progress and status of its constructio

Where Brain, Body and World Collide

The production cross section of electrons from semileptonic decays of beauty hadrons was measured at mid-rapidity (|y| < 0.8) in the transverse momentum range 1 < pt < 8 Gev/c with the ALICE experiment at the CERN LHC in pp collisions at a center of mass energy sqrt{s} = 7 TeV using an integrated luminosity of 2.2 nb^{-1}. Electrons from beauty hadron decays were selected based on the displacement of the decay vertex from the collision vertex. A perturbative QCD calculation agrees with the measurement within uncertainties. The data were extrapolated to the full phase space to determine the total cross section for the production of beauty quark-antiquark pairs