In-line phase-contrast imaging for strong absorbing objects

3D phantom for image quality assessment of mammography systems

Objective.To present an innovative approach for the design of a 3D mammographic phantom for medical equipment quality assessment, estimation of the glandular tissue percentage in the patient's breast, and emulation of microcalcification (μC) breast lesions.Approach.Contrast-to noise ratio (CNR) measurements, as well as spatial resolution and intensity-to-glandularity calibrations under mammography conditions were performed to assess the effectiveness of the phantom. CNR measurements were applied to different groups of calcium hydroxyapatite (HA) and aluminum oxide (AO)μCs ranging from 200 to 600μm. Spatial resolution was characterized using an aluminum plate contained in the phantom and standard linear figures of merit, such as the line spread function and modulation transfer function (MTF). The intensity-to-glandularity calibration was developed using an x-ray attenuation matrix within the phantom to estimate the glandular tissue percentage in a breast with a compressed thickness of 4 cm.Main results.For the prototype studied, the minimum confidence level for detecting HAμCs is 95.4%, while for AOμCs is above 68.3%. It was also possible to determine that the MTF of the commercial mammography machine used for this study at the Nyquist frequency is 41%. Additionally, a one-to-one intensity-to-glandularity calibration was obtained and verified with Monte-Carlo simulation results.Significance.The phantom provides traditional arrangements presented in accreditation phantoms, which makes it competitive with available devices, but excelling in regarding affordability, modularity, and inlays distribution. Moreover, its design allows to be positioned in close proximity to the patient's breast during a medical screening for a simultaneous x-ray imaging, such that the features of the phantom can be used as reference values to specify characteristics of the real breast tissue, such as proportion of glandular/adipose composition and/orμC type and size lesions.

Hard and soft X-ray imaging to resolve human ovarian cortical structures

Laboratory and synchrotron X-ray tomography are powerful tools for non-invasive studies of biological samples at micrometric resolution. In particular, the development of phase contrast imaging is enabling the visualization of sample details with a small range of attenuation coefficients, thus allowing in-depth analyses of anatomical and histological structures. Reproductive medicine is starting to profit from these techniques, mainly applied to animal models. This study reports the first imaging of human ovarian tissue where the samples consisted of surgically obtained millimetre fragments, properly fixed, stained with osmium tetroxide and included in epoxydic resin. Samples were imaged by the use of propagation phase contrast synchrotron radiation micro-computed tomography (microCT), obtained at the SYRMEP beamline of Elettra light source (Trieste, Italy), and X-ray absorption microCT at the Theoretical Biology MicroCT Imaging Laboratory in Vienna, Austria. The reconstructed microCT images were compared with the soft X-ray absorption and phase contrast images acquired at the TwinMic beamline of Elettra in order to help with the identification of structures. The resulting images allow the regions of the cortex and medulla of the ovary to be distinguished, identifying early-stage follicles and visualizing the distribution of blood vessels. The study opens to further application of micro-resolved 3D imaging to improve the understanding of human ovary's structure and support diagnostics as well as advances in reproductive technologies.

Investigation of inner ear anatomy in mouse using X-ray phase contrast tomography

A thorough understanding of inner ear anatomy is important for investigators. However, investigation of the mouse inner ear is difficult due to the limitations of imaging techniques. X-ray phase contrast tomography increases contrast 100-1,000 times compared with conventional X-ray imaging. This study aimed to investigate inner ear anatomy in a fresh post-mortem mouse using X-ray phase contrast tomography and to provide a comprehensive atlas of microstructures with less tissue deformation. All experiments were performed in accordance with our institution's guidelines on the care and use of laboratory animals. A fresh mouse cadaver was scanned immediately after sacrifice using an inline phase contrast tomography system. Slice images were reconstructed using a filtered back-projection (FBP) algorithm. Standardized axial and coronal planes were adjusted with a multi-planar reconstruction method. Some three-dimensional (3D) objects were reconstructed by surface rendering. The characteristic features of microstructures, including otoconia masses of the saccular and utricular maculae, superior and inferior macula cribrosae, single canal, modiolus, and osseous spiral lamina, were described in detail. Spatial positions and relationships of the vestibular structures were exhibited in 3D views. This study investigated mouse inner ear anatomy and provided a standardized presentation of microstructures. In particular, otoconia masses were visualized in their natural status without contrast for the first time. The comprehensive anatomy atlas presented in this study provides an excellent reference for morphology studies of the inner ear.

X-ray phase-contrast imaging: from pre-clinical applications towards clinics

Phase-contrast x-ray imaging (PCI) is an innovative method that is sensitive to the refraction of the x-rays in matter. PCI is particularly adapted to visualize weakly absorbing details like those often encountered in biology and medicine. In past years, PCI has become one of the most used imaging methods in laboratory and preclinical studies: its unique characteristics allow high contrast 3D visualization of thick and complex samples even at high spatial resolution. Applications have covered a wide range of pathologies and organs, and are more and more often performed in vivo. Several techniques are now available to exploit and visualize the phase-contrast: propagation- and analyzer-based, crystal and grating interferometry and non-interferometric methods like the coded aperture. In this review, covering the last five years, we will give an overview of the main theoretical and experimental developments and of the important steps performed towards the clinical implementation of PCI.

Optimization of image recording distances for quantitative X-ray in-line phase contrast imaging

Compared to phase retrieval from single sample-to-detector distance (SDD) image, phase retrieval with multiple SDD images could improve the precision in quantitative X-ray in-line phase contrast imaging (QXIPCI). Among all the related phase retrieval approaches, the two-SDD-image-based one is the simplest and well compromises between precision and dose. However, how to optimize the recording distances for the two images to achieve highest precision, remains unsolved. In this paper, the problem was investigated systematically based on digital simulation and related experiments. Spectral correlation degree (SCD) is introduced to evaluate the pertinence between the two SDD images. The simulation results show that the highest retrieving precision could be obtained while the SDD of the second image is three times that of the first image. The best retrieval could be achieved when SDD of the first image is selected properly, meanwhile the SCD occurs with a typical damping oscillation. Experiments, carried out at the X-ray imaging beamline of SSRF, demonstrated the simulation results.

X-ray phase contrast microscopy at 300 nm resolution with laboratory sources

We report the performance of an X-ray phase contrast microscope for laboratory sources with 300 nm spatial resolution. The microscope is based on a commercial X-ray microfocus source equipped with a planar X-ray waveguide able to produce a sub-micrometer x-ray beam in one dimension. Phase contrast images of representative samples are reported. The achieved contrast and resolution is discussed for different configurations. The proposed approach could represent a simple, inexpensive, solution for sub-micrometer resolution imaging with small laboratory setups.