Conventional contrast agents utilized in diagnostic radiology are based on x-ray absorption properties; alternative physical principles capable of providing a contrast enhancement in radiographs have ...never been applied. This study exploits the possibility of using a novel type of contrast media based on x-ray scattering. The contrast agents consist of microbubble echo-enhancing agents, usually applied in ultrasound examinations, which are invisible with conventional x-ray absorption techniques. The experiment was carried out at the medical beamline of the synchrotron radiation laboratory ELETTRA in Trieste, Italy. A flat silicon analyzer crystal typically used for diffraction-enhanced imaging was utilized as a tool for detecting the scattering properties of the contrast agents. In analyzer-based imaging, it is possible to detect the scattering properties of the sample by shifting the analyzer crystal to selected positions of its reflectivity curve. In particular, when the sample consists of a large number of micro-particles an overall effect can be observed. Phantoms containing contrast agents based on microbubbles were imaged at different angular positions of the analyzer crystal. High visibility of the details was demonstrated, and a strong contrast enhancement was measured compared to normal x-ray absorption techniques.
X-rays are commonly used as a means to image the inside of objects opaque to visible light, as their short wavelength allows penetration through matter and the formation of high spatial resolution ...images. This physical effect has found particular importance in medicine where x-ray based imaging is routinely used as a diagnostic tool. Increasingly, however, imaging modalities that provide functional as well as morphological information are required. In this study the potential to use x-ray phase based imaging as a functional modality through the use of microbubbles that can be targeted to specific biological processes is explored. We show that the concentration of a microbubble suspension can be monitored quantitatively whilst in flow using x-ray phase contrast imaging. This could provide the basis for a dynamic imaging technique that combines the tissue penetration, spatial resolution, and high contrast of x-ray phase based imaging with the functional information offered by targeted imaging modalities.
X-ray phase contrast imaging (XPCi) methods are sensitive to phase in addition to attenuation effects and, therefore, can achieve improved image contrast for weakly attenuating materials, such as ...often encountered in biomedical applications. Several XPCi methods exist, most of which have already been implemented in computed tomographic (CT) modality, thus allowing volumetric imaging. The Edge Illumination (EI) XPCi method had, until now, not been implemented as a CT modality. This article provides indications that quantitative 3D maps of an object's phase and attenuation can be reconstructed from EI XPCi measurements. Moreover, a theory for the reconstruction of combined phase and attenuation maps is presented. Both reconstruction strategies find applications in tissue characterisation and the identification of faint, weakly attenuating details. Experimental results for wires of known materials and for a biological object validate the theory and confirm the superiority of the phase over conventional, attenuation-based image contrast.
In analyzer based imaging (ABI) scattering can be efficiently separated from refraction and absorption effects by acquiring three images of the sample. In the scattering image the lungs appear as ...areas of high intensity signal (area contrast), which is modulated by the local thickness of the scattering tissue intersecting the X-ray path. The scattering signal is also included in the so-called apparent absorption image, where it adds to the absorption contrast thanks to the extinction of rays which are deviated outside the analyzer crystal's acceptance window. The presence of scattering can be emphasized in the ratio between two images acquired with a strongly detuned and a perfectly tuned analyzer crystal, respectively: we name this ratio as the amplified scatter image. In this paper we present ABI scattering methods applied to postmortem mouse lung imaging to assess their diagnostic value. For this purpose images have been acquired at the SYRMEP beamline of the ELETTRA synchrotron in Trieste (Italy) with the Argus time delay integration CCD detector at a photon energy of 25 keV . Subsequently the parametric images, including the amplified scatter image have been obtained, and contrast and signal-to-noise ratio have been evaluated. It is noteworthy that images have been acquired with a radiation dose of some mGy, thus are compatible with dose restricted medical imaging settings such as mammography.
Thanks to their high detection efficiency and low intrinsic noise, direct conversion X-ray Photon Counting Detectors (XPCDs) are particularly suitable for low dose imaging applications such as ...mammography. The photon counting technology can implement also two or more acquisition thresholds to perform single-shot spectral imaging with one polychromatic source. However, XPCDs with thick high Z crystal sensor and small pixel size are affected by the charge sharing effect. This issue can induce multiple counts from a single interaction reducing both spectral and spatial resolutions. In a pure counting mode, multiple counts from charge sharing can be partially or totally removed by increasing the acquisition threshold at the cost of a loss of efficiency. Thus, the performances of XPCDs can be threshold-dependent. New generation XPCDs implement solutions to cope with charge sharing issue. If the charge sharing is properly corrected, no multiple counts are recorded and the performances (detection efficiency, spectral and spatial resolutions) of the acquisition system are expected to be independent from the acquisition threshold. This work presents a study of a Pixirad-1 detection system based on a CdTe Schottky sensor and PIXIE-III readout system. This chip can be configured in three different operation modes, two of which implement solutions to remove multiple counts. Using monochromatic radiation, the performances of these different operation modes have been compared trough a measure of the integral spectra and the Signal to Noise Ratio (SNR) as function of the acquisition threshold.
Abstract
X-ray propagation-based phase-contrast imaging is an attractive phase-sensitive imaging technique that has found applications in many research fields. Here, we report the investigations of a ...method which can quantitatively reconstruct in 3D the refractive index decrement of a quasi-homogeneous object using single-distance phase-contrast tomography data. The method extends the Born-type approximation phase-retrieval algorithm, which is based on the phase-attenuation duality (ε = δ/β, with constant ε) and suitable for homogeneous objects, to tomography and we study its application to quasi-homogeneous objects. The noise performance and the phase-attenuation duality influences of the method are also investigated. In simulation, the method allows us to quantitatively reconstruct the 3D refractive index decrement for quasi-homogeneous and weakly absorbing samples and it performs well in the practical noise situation. Furthermore, it shows a substantial contrast increase and successfully distinguishes different materials in a quasi-homogeneous and weakly absorbing sample from experimental data, even with inappropriate ε value.
The measurement of the linear attenuation coefficients of breast tissues is of fundamental importance in the field of breast x-ray diagnostic imaging. Different groups have evaluated the linear ...attenuation coefficients of breast tissues by carrying out direct attenuation measurements in which the specimens were thin and selected as homogeneous as possible. Here, we use monochromatic and high-intensity synchrotron radiation computed tomography (SR CT) to evaluate the linear attenuation coefficients of surgical breast tissues in the energy range from 15 to 26.5 keV. X-ray detection is performed by a custom digital silicon micro-strip device, developed in the framework of the PICASSO INFN experiment. Twenty-three human surgical breast samples were selected for SR CT and histological study. Six of them underwent CT, both as fresh tissue and after formalin fixation, while the remaining 17 were imaged only as formalin-fixed tissues. Our results for fat and fibrous tissues are in good agreement with the published values. However, in contrast to the published data, our measurements show no significant differences between fibrous and tumor tissues. Moreover, our results for fresh and formalin-fixed tissues demonstrate a reduction of the linear attenuation coefficient for fibrous and tumor tissues after fixation.
Context. Consistent modeling of protoplanetary disks requires the simultaneous solution of both continuum and line radiative transfer, heating and cooling balance between dust and gas and, of course, ...chemistry. Such models depend on panchromatic observations that can provide a complete description of the physical and chemical properties and energy balance of protoplanetary systems. Along these lines, we present a homogeneous, panchromatic collection of data on a sample of 85 T Tauri and Herbig Ae objects for which data cover a range from X-rays to centimeter wavelengths. Datasets consist of photometric measurements, spectra, along with results from the data analysis such as line fluxes from atomic and molecular transitions. Additional properties resulting from modeling of the sources such as disk mass and shape parameters, dust size, and polycyclic aromatic hydrocarbon (PAH) properties are also provided for completeness. Aim. The purpose of this data collection is to provide a solid base that can enable consistent modeling of the properties of protoplanetary disks. To this end, we performed an unbiased collection of publicly available data that were combined to homogeneous datasets adopting consistent criteria. Targets were selected based on both their properties and the availability of data. Methods. Data from more than 50 different telescopes and facilities were retrieved and combined in homogeneous datasets directly from public data archives or after being extracted from more than 100 published articles. X-ray data for a subset of 56 sources represent an exception as they were reduced from scratch and are presented here for the first time. Results. Compiled datasets, along with a subset of continuum and emission-line models are stored in a dedicated database and distributed through a publicly accessible online system. All datasets contain metadata descriptors that allow us to track them back to their original resources. The graphical user interface of the online system allows the user to visually inspect individual objects but also compare between datasets and models. It also offers to the user the possibility to download any of the stored data and metadata for further processing.
SYRMA-3D (SYnchrotron Radiation MAmmography 3D) aims to develop a breast CT system based on monochromatic synchrotron radiation and a single photon counting detector (PIXIRAD-8) with CdTe sensor. Due ...to the demanding requests on high contrast resolution and low dose, images in breast CT are particularly sensitive to small imperfections of the flat field correction applied before the CT reconstruction. Detectors based on high Z crystal sensors show inhomogeneous pixels gain, which depends on the time from the switching-on of the high voltage polarization. This effect has been studied in our CdTe detector with the purpose of develop an effective flat field correction procedure. In the PIXIRAD-8 detector, the time-dependent inhomogeneities of the flat field signal appear to be local, small and systematically reproducible, with the exception of the pixels on the sensors edges.
Autosomal dominant lateral temporal epilepsy (ADLTE) is characterized by focal seizures with auditory features or aphasia. Mutations in the LGI1 gene have been reported in up to 50% of ADLTE ...pedigrees. We report a family with temporal lobe epilepsy characterized by psychic symptoms associated with a novel LGI1 mutation.
All participants were personally interviewed and underwent neurologic examination and video-EEG recordings. LGI1 exons were sequenced by standard methods. Mutant cDNA was transfected into human embryonic kidney 293 cells; both cell lysates and media were analyzed by Western blot. In silico modeling of the Lgi1 protein EPTP domain was carried out using the structure of WD repeat protein and manually refined.
Three affected family members were ascertained, 2 of whom had temporal epilepsy with psychic symptoms (déjà vu, fear) but no auditory or aphasic phenomena, while the third had complex partial seizures without any aura. In all patients, we found a novel LGI1 mutation, Arg407Cys, which did not hamper protein secretion in vitro. Mapping of the mutation on a 3-dimensional protein model showed that this mutation does not induce large structural rearrangements but could destabilize interactions of Lgi1 with target proteins.
The Arg407Cys is the first mutation with no effect on Lgi1 protein secretion. The uncommon, isolated psychic symptoms associated with it suggests that ADLTE encompasses a wider range of auras of temporal origin than hitherto reported.
PDF
