161 research outputs found
Dual energy imaging in mammography: Cross-talk study in a Si array detector
Abstract One of the main limitation to the extensive use of breast-cancer screening as a prevention method is the relatively high X-ray dose released to the patient. A new approach is under study in which two quasi-monochromatic beamswith mean energies of 18.0 and 36.0 keV -are produced simultaneously, starting from an X-ray tube, by means of a monochromator based on a pyrolytic graphite crystal. The two beams are superimposed in space. The removal of the energy components with low content of diagnostic information from the spectrum, leads to a reduction of the dose released to patients maintaining (or improving) the image quality. The two quasi-monochromatic beams impinge on the patient and then are detected with a solid-state array detector; the image results as the difference between the transmitted intensities of the two detected beams. In this work, the performances of two different electronic readouts and three pixel widths of a silicon position sensitive array detector are simulated and described in order to minimize cross-talk effects between adjacent pixels. The use of a detector with spectrometric capabilities is necessary to separate, by means of thresholds, the high energy photons from the low energy ones
EuroGammaS gamma characterisation system for ELI-NP-GBS: The nuclear resonance scattering technique
A Gamma Beam Characterisation System has been designed by the EuroGammaS association for thecommissioning and development of the Extreme Light Infrastructure-Nuclear Physics Gamma Beam System(ELI-NP-GBS) to be installed in Magurele, Romania. The characterisation system consists of four elements: aCompton spectrometer, a sampling calorimeter, a nuclear resonant scattering spectrometer (NRSS) and a beamprofile imager. In this paper, the nuclear resonant scattering spectrometer system, designed to perform anabsolute energy calibration for the gamma beam, will be describe
Influence of the serotonin transporter 5HTTLPR polymorphism on symptom severity in irritable bowel syndrome
5HTTLPR polymorphism of serotonin transporter yields short (S) and long (L) alleles. SS and LS genotypes are associated with reduced expression of serotonin transporter. This cross-sectional study investigated the association of 5HTTLPR with symptom severity of irritable bowel syndrome (IBS). Patients with IBS (Rome III) and healthy controls were included. Genomic DNA was extracted from saliva, and 5HTTLPR alleles were assessed by polymerase chain reaction. IBS symptom severity was evaluated by means of IBS-SSS questionnaire. Two hundreds and four IBS patients (159 females; mean age: 39.6±12.3 years; 106 with constipation: C-IBS; 98 with diarrhea: D-IBS) and 200 healthy controls (154 females; mean age: 40.4±15.8 years) were enrolled. The overall IBS-SSS value was higher in LS/SS than LL patients (319.0±71.5 versus 283.8±62.3; P = 0.0006). LS/SS patients had also higher values of abdominal pain (59.7±21.0 versus 51.0±18.8; P = 0.020) and bowel dissatisfaction (80.1±23.9 versus 70.5±22.8; P = 0.035). The overall IBS-SSS values in C-IBS and D-IBS patients were 317.2±68.3 and 296.1±71.4, respectively (P = 0.192), with significantly higher values for abdominal distension (65.0±24.4 versus 51.4±24.8; P = 0.0006), but not for bowel dissatisfaction (80.5±21.7 versus 72.9±25.7; P = 0.138). Frequencies of 5HTTLPR genotypes did not differ significantly when comparing IBS patients (overall or upon stratification in C-IBS and D-IBS) with healthy controls. In conclusion, the LS and SS genotypes are significantly correlated with IBS symptom severity, although their possible direct causal role remains to be proven. In addition, the present findings do not support an association of 5HTTLPR with IBS or its clinical presentation in terms of bowel habit predominance
Silicon strip detectors for two-dimensional soft X-ray imaging at normal incidence
A simple prototype system for static two-dimensional soft X-ray imaging using silicon microstrip detectors irradiated at normal incidence is presented. Radiation sensors consist of single-sided silicon detectors made from 300 mum thick wafers, read by RX64 ASICs. Data acquisition and control is performed by a Windows PC workstation running dedicated LabVIEW routines, connected to the sensors through a PCI-DIO-96 interface. Two-dimensional images are obtained by scanning a lead collimator with a thin slit perpendicular to the strip axis, along the whole detector size; the several strip profiles (slices) taken at each position are then put together to form a planar image. Preliminary results are presented, illustrating the high-resolution imaging capabilities of the system with soft X-rays. (C) 2003 Elsevier B.V. All rights reserved.info:eu-repo/semantics/publishedVersio
The SPARC-LAB Thomson source commissioning
Abstract
The SPARC_LAB Thomson source is presently under commissioning at LNF. An electron beam of energy between 30-150 MeV collides head-on with the laser pulse provided by the Ti:Sapphire laser FLAME, characterized in this phase by a length of 6 ps FWHM and by an energy ranging between 1 and 5 J. The key features of this system are the wide range of tunability of the X- rays yield energy, i.e. 20-500 keV, and the availability of a coupled quadrupole and solenoid focusing system, allowing to reach an electron beam size of 10-20 microns at the interaction point. The experimental results obtained in the February 2014 shifts are presented
Collimation and characterization of ELI-NP gamma beam
The ELI-NP facility, currently being built in Bucharest, Romania, will deliver an intense and almost monochromatic gamma beam with tunable energy between 0.2 and 20 MeV. The challenging energy bandwidth of [Formula: see text]0.5% will be adjusted through the collimation system, while the main beam parameters will be measured through a devoted gamma-beam characterization system.[Formula: see text] The gamma-beam characterization system, designed by the EuroGammaS collaboration, consists of four elements: a Compton spectrometer that measures the gamma energy spectrum; a sampling calorimeter for a fast combined measurement of the beam average energy and its intensity, which will be used also as a monitor during machine commissioning and development; a nuclear resonant scattering system for absolute energy inter-calibration of the other detectors; and a gamma beam profile imager to be used for alignment and diagnostics purposes. The collimation and characterization system will be presented in this article. These systems have already been built and tested, while the delivery at ELI-NP facility and the final commissioning is scheduled by Fall 2018
MariX, an advanced MHz-class repetition rate X-ray source for linear regime time-resolved spectroscopy and photon scattering
The need of a fs-scale pulsed, high repetition rate, X-ray source for time-resolved fine analysis of matter
(spectroscopy and photon scattering) in the linear response regime is addressed by the conceptual design of a
facility called MariX (Multi-disciplinary Advanced Research Infrastructure for the generation and application of
X-rays) outperforming current X-ray sources for the declared scope. MariX is based on the original design of a
two-pass two-way superconducting linear electron accelerator, equipped with an arc compressor, to be operated
in CW mode (1 MHz). MariX provides FEL emission in the range 0.2–8 keV with 108 photons per pulse ideally
suited for photoelectric effect and inelastic X-ray scattering experiments. The accelerator complex includes an
early stage that supports an advanced inverse Compton source of very high-flux hard X-rays of energies up
to 180 keV that is well adapted for large area radiological imaging, realizing a broad science programme and
serving a multidisciplinary user community, covering fundamental science of matter and application to life
sciences, including health at preclinical and clinical level
Technical Design Report EuroGammaS proposal for the ELI-NP Gamma beam System
The machine described in this document is an advanced Source of up to 20 MeV
Gamma Rays based on Compton back-scattering, i.e. collision of an intense high
power laser beam and a high brightness electron beam with maximum kinetic
energy of about 720 MeV. Fully equipped with collimation and characterization
systems, in order to generate, form and fully measure the physical
characteristics of the produced Gamma Ray beam. The quality, i.e. phase space
density, of the two colliding beams will be such that the emitted Gamma ray
beam is characterized by energy tunability, spectral density, bandwidth,
polarization, divergence and brilliance compatible with the requested
performances of the ELI-NP user facility, to be built in Romania as the Nuclear
Physics oriented Pillar of the European Extreme Light Infrastructure. This
document illustrates the Technical Design finally produced by the EuroGammaS
Collaboration, after a thorough investigation of the machine expected
performances within the constraints imposed by the ELI-NP tender for the Gamma
Beam System (ELI-NP-GBS), in terms of available budget, deadlines for machine
completion and performance achievement, compatibility with lay-out and
characteristics of the planned civil engineering
An ultrasound model to calculate the brain blood outflow through collateral vessels: a pilot study
A musical matter of life and death: the morality of mortality and the coverage of Amy Winehouse's death in the UK press
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