Dual-energy radiography is an effective technique that allows removal of contrast between pairs of materials in order to display details of interest on a uniform background. In mammographic images ...the detection of small nodules is often impeded by obscuring background 'clutter' resulting from the contrast between normal tissues (glandular and adipose) in their neighbourhood. We consider whether it could be possible to apply dual-energy radiography to the breast, which is hypothetically principally composed of three tissues, glandular, adipose and cancerous, in order to remove the contrast due to the distribution of normal tissues and, as a consequence, to enhance the intrinsic contrast of the pathology. The purpose of this work is to test the limitations of dual-energy radiography on a three-component phantom under optimum conditions of the source and detector. We use a synchrotron monochromatic beam, produced at the ELETTRA synchrotron facility (Trieste, Italy), and an imaging plate detector, in order to acquire two images at low and high energies of a phantom composed of polyethylene, plexiglas and water. For evaluation of the potential of this procedure we studied the signal-to-noise ratio (SNR) of polyethylene and water on a set of images obtained by applying the dual-energy procedure. We found that the SNR of polyethylene and water is around the detectability threshold (according to Rose's criteria) at the contrast cancellation angles. Finally we evaluated the air entrance dose required for this double exposure, resulting in 0.81 mGy for the low-energy image and 0.01 mGy for the high-energy image. To obtain the same image quality for a standard breast of 5.5 cm, mean glandular doses of 3.50 mGy and 0.03 mGy at 17 keV and at 34 keV, respectively, are required.
A Gamma Beam Characterisation System has been designed by the EuroGammaS association for the commissioning 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: a Compton spectrometer, a sampling calorimeter, a nuclear resonant scattering spectrometer (NRSS) and a beam profile imager. In this paper, the nuclear resonant scattering spectrometer system, designed to perform an absolute energy calibration for the gamma beam, will be described.
•Gamma Beam Characterisation System.•Fast detection system based on BaF2 crystals.•Absolute Gamma energy calibration based on Nuclear Resonant Scattering.
To determine the feasibility of using synchrotron radiation (SR) in diagnostic mammography.
Monochromatic SR of x-ray beams of selected energies of 14-20 keV were used to obtain mammograms of ...surgically removed breast specimens that contained tumor nodules. For comparison, conventional mammograms of the same specimens were also obtained.
The mammograms obtained with SR had higher contrast and better resolution than did traditional mammograms and demonstrated excellent detail in all cases studied. The mean glandular doses at 17 and 18 keV were 1.56 and 0.83 mGy, respectively, which is compatible with the mean value of 1.41 mGy delivered with the conventional grid apparatus.
SR mammography appears to be a promising diagnostic imaging technique.
A novel digital x-ray detector has been assembled. The imaging system is based on a phosphor-coated charge-coupled device (CCD) obtained by direct deposition of a gadolinium oxysulphide scintillator ...onto the detector surface. The modulation transfer function has been measured along the two directions of the digital coordinates with the narrow slit technique. A resolution limit of about 20 line pairs per mm has been obtained for both directions. The high spatial resolution currently demanded in mammography can be achieved with this imaging system.
Narrow energy band X-rays via mosaic crystal for mammography application Gambaccini, M.; Taibi, A.; Del Guerra, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/1995, Volume:
365, Issue:
1
Journal Article
Peer reviewed
Monochromatic X-ray beams are desirable in various fields of diagnostic radiology. We are investigating an imaging system based on a narrow energy band X-ray source for mammography application. The ...narrow energy band is obtained by making use of a mosaic crystal that reflects X-rays from a conventional X-ray tube via Bragg diffraction. In this paper the characteristics of the system in terms of energy resolution and fluence rate are reported. Small field (1.1 × 3.0 cm2) radiographs of Plexiglas phantoms with a thickness up to 3.6 cm have been obtained with 18, 20 and 22 keV quasi-monochromatic beams. The field size is limited by the crystal size along one dimension and by the desired energy spread along the other one. A digital imaging system has been used to correct for non-uniformity of the X-ray beam.
Purpose:
A 3-year project called LABSYNC has been recently funded by the European Commission, with the aim of designing a radiation facility based on a compact light source, i.e., a laboratory-sized ...commercial synchrotron, capable of accelerating electrons up to 6 or 20 MeV. An accurate spectral description of hard x rays emitted from thin targets, irradiated by electron beams circulating in the storage ring, is of primary interest for the design and the characterization of a beamline. This article, Part I, aims at optimizing some of the parameters which are critical for the design of medical applications based on the above compact light source. The goal was to evaluate the dependence of photon fluence and beam monochromaticity on electron-beam energy, target material, and thickness.
Methods:
The transport of 6 and 20 MeV electrons in a thin molybdenum, rhodium, and tungsten target is studied by means of Monte Carlo simulations using
MCNPX
. Configurations of the x-ray output port, different from the default forward-directed emission of the beam, are also investigated. A comparison with reference spectra for general diagnostic radiology and mammography is carried out.
Results:
It is shown that the emitted x-ray beams can be far more intense than those generated by conventional x-ray tubes for radiography applications. The profiles of the calculated polychromatic spectra resemble those generated by conventional x-ray tubes, with x-ray energies up to the energy of the incident-electron beam. An appreciable improvement in the monochromaticity of the beams can be obtained by viewing the x-ray emission from an output port antiparallel to the direction of the incident-electron beam.
Conclusions:
The optimum target thickness for tungsten target spectra is practically constrained by a trade-off between bremsstrahlung efficiency and focal-spot size requirements. A larger margin for optimization of target thickness is probably available for mammographic spectra. The constraint of a backward-directed (or, to a lesser extent, orthogonal) output port is to be considered mandatory for minimizing the high-energy tail of the spectral distribution and keeping the radiation dose to a reasonable level. It is also fundamental to evaluate the impact of the high-energy tail of the emitted spectra in x-ray imaging applications, since the energy range involved is significantly beyond the diagnostic range. This topic will be dealt with in Part II of the article.
Children with severe food allergy may present high risk of fatal anaphylaxis and a highly impaired quality of life. Anti IgE-treatment has been shown to be a promising approach as monotherapy for ...severe allergy to multiple foods. However, very high serum total IgE levels may limit its use.
This study aims to assess the efficacy of IgE-selective immunoadsorption (IgE-IA) on total IgE levels and threshold of reactivity to the culprit foods in children with history of severe anaphylaxis due to multiple foods and allergic comorbidities.
In this single-center, prospective, open-label efficacy study we evaluated children with severe asthma, allergy to 2+foods and total IgE levels >2300 kUI/L. To establish the food reactivity threshold, each patient underwent oral food challenges (OFCs) before and after IgE-IA.
Five patients (4 males; age, 12.2 ± 5 years, mean ± SD) underwent an average of 3 (range 2–4) sessions of IgE-IA. Each session reduced IgE levels by a mean of 1958.87 kUI/L. After the IgE-IA cycle, serum total IgE dropped from 3948 ± 1652.7 (mean ± SD) to 360.8 ± 71.9 kUI/L (−10.9 folds; p = 0.01). The threshold of reactivity (No Observed Adverse Effect Level, NOAEL) tested at OFCs for the culprit foods (4 baked-milk + 2 baked-egg + 1 lentil + 2 hazelnut + 1 wheat) increased overall from 21.5 (median, IQR 1.5–82.6) protein milligrams to 1115 (837.2–4222.8) milligrams (p < 0.001), ie, up to 51.8 times higher than baseline. 8/10 OFCs were negative after IgE-IA.
IgE-IA increased food threshold quickly. It can be considered in well-selected patients with severe food allergies and high IgE-levels especially if otherwise eligible to anti IgE treatment.
Measurement of focal spot size in a 5.5 MeV linac Gambaccini, M.; Cardarelli, P.; Taibi, A. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
05/2011, Volume:
269, Issue:
10
Journal Article
Peer reviewed
High energy X-ray beams allow to perform analysis on different materials and objects of relevant interest that cannot be investigated with conventional X-ray sources. A 5.5
MeV endpoint energy ...bremsstrahlung source has been characterized by evaluating the size of X-ray emitting area. In order to perform a proper characterization, an ‘ad hoc’ slit-camera has been designed and a specific technique has been adopted. Due to the characteristics of the beam, a highly attenuating slit with variable aperture has been designed using Monte Carlo simulations of the X-ray beam and set up. Since the slit camera is far from the ideal model (negligible X-ray transmission and very thin aperture), a whole set of image profiles of the slit at different width sizes have been acquired and analyzed. Imaging correction procedures and data fitting lead to satisfactory experimental results according to the theoretical model.
PDF
