The main purpose of the SYRMEP (SYnchrotron Radiation for MEdical Physics) research team is the investigation and development of innovative techniques for medical imaging. A dedicated beamline has ...been built at ELETTRA to evaluate the effectiveness of synchrotron-based techniques in medical radiology with particular interest to mammography, and more in general, to the imaging of biological and biomedical samples, either in planar or tomographic set-ups. Taking advantage of the high intensity and high spatial coherence of Synchrotron Radiation (SR), phase sensitive techniques such as Phase Contrast (PhC) and Diffraction Enhanced Imaging (DEI) can be applied. After successful studies carried out on test objects and in vitro samples, the research in mammography is aiming at in vivo clinical trials. For this purpose, the layout of the SYRMEP beamline has been substantially modified and the safety system has been completely redesigned to guarantee the compliance with current radiation protection guidelines. In the present paper, the main characteristics of the beamline and an overview of the results obtained in different contexts of biomedical imaging are presented. Moreover, the status of the project for clinical mammography is outlined.
Effect of spatial coherence on the application of in-line phase contrast imaging (IL-PCI) to synchrotron radiation (SR) mammography is investigated experimentally at SYRMEP/ELETTRA. Factors that are ...related to spatial coherence and IL-PCI image quality, which include vertical and horizontal beam, photon energy, slit width, sample–detector distance and detector resolution, are analyzed. The experimental results demonstrate that better IL-PCI image quality could be achieved in the vertical beam. As for the slit width, the spatial coherence for horizontal beam remains almost the same until the slit width is gradually closed to 5
mm. For mammography applications of IL-PCI, slit width of 100
mm could be employed and high-enough image quality can still be obtained. Lower photon energy results in better coherence and correspondingly better IL-PCI image quality. By compromising the dose and image quality, photon energy of ∼19
keV is recommended for SR mammography. To preserve the edge enhancement resulting from good coherence of SR, an appropriate sample–detector distance and a practical detector should be selected. The optimum sample–detector distance highly depends on detector resolution. For high-resolution film, the best IL-PCI imaging quality is obtained at a closer sample–detector distance. For an X-ray CCD with pixel size of 14
μm, about 1.5
m is needed to achieve optimum image quality. The large pixel size of the detector will deteriorate the edge-enhancing efficiency and results in lower IL-PCI imaging quality. In practice, the spatial resolution and sensitivity of the detectors should be compromised.
Even though the potential of phase contrast (PC) imaging has been demonstrated in a number of biological tissue samples, the availability of free-space propagation phase contrast images of real ...breast tumours is still limited. The aim of this study was to obtain phase contrast images of two different pathological breast specimens containing tumours of differing morphological type at two synchrotron radiation (SR) facilities, and to assess any qualitative improvements in the evaluation and characterisation of the masses through the use of phase contrast imaging.
A second aim was to assess the effects of parameters such as detector resolution, beam energy and sample-to-detector distance on image quality using the same breast specimens, as to date these effects have been modelled and discussed only for geometric phantoms. At each synchrotron radiation facility a range of images was acquired with different detectors and by varying the above parameters. Images of the same samples were also acquired with the absorption-based approach to allow a direct comparison and estimation of the advantages specifically ascribable to the PC technique.
Purpose
Phase-contrast mammography with synchrotron radiation is an innovative X-ray imaging practice that improves the identification of breast lesions. Previous studies have proven the superiority ...of the mammography images taken in the phase-contrast modality using synchrotron radiation beams as compared with images taken in conventional mammography by subjective analyses. However, to our knowledge, no previous study has compared different acquisition systems in order to quantify this improvement by means of objective robust indicators. In this research, we intend to quantify the superiority of phase-contrast imaging by means of objective metrics of image quality.
Methods
Images from the American College of Radiology Mammographic Accreditation Phantom were obtained at hospitals, in two digital mammography equipment and at the Elettra synchrotron radiation facility (Trieste, Italy), using free space propagation phase-contrast modality. Regions of interest were selected to analyze image quality at the fibers (phase object) and masses (area object) simulated on the phantom by means of the signal-to-noise ratio, the figure of merit, the contrast and the edge visibility.
Results
The image contrast and edge visibility were significantly higher at the phase-contrast modality as compared with digital mammography equipment. The figure of merit using phase-contrast modality was higher for the fibers and comparable for the masses.
Conclusion
The results showed an improvement of the contrast and edge visibility in phase-contrast images. These improvements may be important in the detection of small lesions and details.
Introduction The Abdus Salam International Centre for Theoretical Physics (ICTP) and the Trieste University have initiated in 2014 a Master of Advanced Studies in Medical Physics a two-years training ...programme in Medical Physics. The programme is designated to provide young promising graduates in physics, mainly from developing countries, with a post-graduated theoretical and clinical training suitable to be recognised as Clinical Medical Physicist in their countries. Presently, the 3 cycles of the programme has seen 49 participants from 33 Countries: Africa (19), Asia (11), Central and South America (14), and Europe (5), selected from more than 400 applicants per year. Scholarships are awarded to candidates from developing countries with support of the IAEA, TWAS, KFAS, IOMP, EFOMP and ICTP. Material and methods The programme is developed following the recommendations of IOMP and IAEA for education and clinical training. In the first year 332 lectures and 228 h of exercises are devoted to all main fields of medical physics. The second year is spent in one of the 12 medical physics department of the hospitals’ network for the clinical training in: radiation oncology or diagnostic and nuclear medicine, on a programme developed adapting the IAEA (TCS37, TCS47 and TCS50) and AFRA guidelines. Conclusions IOMP, EFOMP and IAEA are seeing this initiative as an answer to the growing demand of Medical Physicists in developing Countries, representing an important European contribution to the development of medical physics in the developing world.
We propose a set of standard assumptions for the modelling of Class II and III protoplanetary disks, which includes detailed continuum radiative transfer, thermo-chemical modelling of gas and ice, ...and line radiative transfer from optical to cm wavelengths. The first paper of this series focuses on the assumptions about the shape of the disk, the dust opacities, dust settling, and polycyclic aromatic hydrocarbons (PAHs). In particular, we propose new standard dust opacities for disk models, we present a simplified treatment of PAHs in radiative equilibrium which is sufficient to reproduce the PAH emission features, and we suggest using a simple yet physically justified treatment of dust settling. We propose to use line observations of robust chemical tracers of the gas, such as O, CO, and H2, as additional constraints to determine a number of key properties of the disks, such as disk shape and mass, opacities, and the dust/gas ratio, by simultaneously fitting continuum and line observations.
Charge sharing plays an important role in the performance of single-photon counting microstrip detectors, since the comparator threshold defines the effective pixel width. In this contribution, the ...PICASSO (Phase Imaging for Clinical Application with Silicon detector and Synchrotron radiatiOn) single-photon counting microstrip detector oriented in edge-on configuration has been used to study its spatial resolution as a function of the comparator threshold. The experiment was carried out with monochromatic x-rays at the SYRMEP beamline of the Elettra synchrotron radiation facility in Trieste (Italy). The Edge Spread Function (i.e. the integral of the Line spread Function, LSF) was measured by horizontally translating vertical slits from a bar-pattern test-object in front of the detector, at four different photon energies (19, 20, 22, and 25 keV) and for several different values of the comparator threshold. The effect of charge sharing between strips on the spatial resolution has been quantified by calculating the horizontal Modulation Transfer Function (MTF). Moreover, the composite LSF from neighboring pixels was obtained: this allowed estimating the optimal threshold for each photon energy by selecting the threshold at which the composite LSF would approach unity along the entire width of the pixel. The results show that at thresholds lower than half of the photon energy, charge sharing increases the effective pixel width, causing a drop of the MTF, and it is responsible for the appearance of peaks in the composite LSF. Conversely, at thresholds higher than half of the photon energy, the effective pixel width is reduced and the spatial resolution is increased, but the collection efficiency is compromised, as demonstrated by the presence of valleys in the composite LSF.
X-ray Photon Counting Detectors (XPCDs) with thick semiconductor sensors and small pixel sizes suffer from a charge-sharing effect which can induce multiple counts from a single interacting photon. ...This issue degrades not only the energy resolution, but it also worsens the spatial resolution. Multiple counts can be removed by acting on the discriminator threshold or they can be corrected by means of specific acquisition modalities implemented in the readout electronics. In this paper we present the results of the characterization of the Pixirad-1/Pixie-III device, a XPCD carrying a 650μm thick CdTe sensor with a small pixel (62×62μm2). The Pixie-III readout system includes programmable energy thresholds and it implements three acquisition modes: a pure photon counting mode and two modes specially designed to correct charge-sharing effects. The measured energy resolution of the three acquisition modes for different energies are here reported. Moreover, we characterize the imaging performance for different combinations of acquisition modes and thresholds by measuring the presampling Modulation Transfer Function (MTF), the Normalized Noise Power Spectrum (NNPS) and by assessing the Noise Equivalent number of Quanta (NEQ).
Conventional X-ray medical imaging makes use of the transmission properties of the sample. On the other hand, recently introduced phase-sensitive techniques take advantage of the phase shifts that ...occur when an electromagnetic wave encounters different refraction indices. Diffraction-Enhanced Imaging (DEI) is a phase-sensitive X-ray imaging technique based on the use of an analyzer placed between the sample and the detector. DEI performed at several synchrotron radiation facilities worldwide has proven outstanding image quality both in material science and medical imaging. At the medical imaging beamline SYRMEP under operation at the synchrotron radiation facility ELETTRA (Trieste, Italy), an analyzer system has been implemented to perform DEI. Experiments to evaluate the associated improvements in image quality were carried out on phantoms and biological samples and to prove that DEI is an appropriate tool for studying refraction and scattering properties. The results observed on the examples reported in this work suggest that the edge-enhancement effects and the superior sensitivity to soft tissue make DEI a valuable tool for early diagnosis of subtle diseases in many different fields.
Introduction The first clinical trial of phase-contrast mammography with monochromatic beam was performed at Elettra, the Italian Synchrotron Radiation facility. A lower Mean Glandular Dose (MGD) and ...a higher specificity were achieved compared to the digital mammography for the patient cohort (more than 70). Purpose The SYRMA-CT project (SYnchrotron Radiation for MAmmography – Computed Tomography) aims to perform the first clinical trial of phase-sensitive breast CT with monochromatic beam. High image quality and low dose are expected according to the results of the first mammography trial. Materials and methods A large area CdTe single photon counting detector (PIXIRAD-8) is used. Phase-retrieval algorithm are applied, thus exploiting propagation based phase-contrast imaging (PPCI). The dose system of the beamline has been calibrated to match the energy requirement up to 40 keV. Due to the peculiar irradiation modality, ad hoc Monte Carlo simulations and experimental measurements were performed for dose evaluation. Results Images of surgical samples included in large test objects (up to 12 cm diameter) were acquired at 38 keV in clinical compatible dose conditions (MGD ∼5 mGy). Phase-retrieval pre-processing was applied improving the CNR of the high-resolution images with (120 μm)3 voxel size. Conclusion The upgrade of the mammographic facility of the Elettra laboratory towards a new clinical trial is going on. Image quality and dose assessment indicate its feasibility with monochromatic beam. This clinical trial will allow the evaluation of PPCI breast CT in optimal conditions and will give indication for the translation to the hospital of phase-sensitive techniques. Disclosure Nothing to declare.
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