Paul Scherrer Institut

Koninklijke Philips Corporation N.V.

Chinese Academy of Sciences

Institute of High Energy Physics

Marco Stampanoni

Zhentian Wang

Matias Kagias

Thomas Koehler

Ewald Roessl

Christian David

Ziyu Wu

Peiping Zhu

Konstantins Jefimovs

Matthias Bartels

Joan Vila Comamala

Lucia Romano

Carolina Arboleda

Thomas THÜRING

Elements of photonic devices with high aspect ratio patterns are fabricated. A stabilizing catalyst that forms a stable metal-semiconductor alloy allows to etch a substrate in vertical direction even at very low oxidant concentration without external bias or magnetic field. A metal layer on the substrate reacts with the oxidant contained in air and catalyzes the semiconductor etching by the etchant. Air in continuous flow at the metal layer allows to maintain constant the oxidant concentration in proximity of the metal layer. The process can continue for a long time in order to form very high aspect ratio structures in the order of 10,000:1. Once the etched semiconductor structure is formed, the continuous air flow supports the reactant species diffusing through the etched semiconductor structure to maintain a uniform etching rate. The continuous air flow supports the diffusion of reaction by-products to avoid poisoning of the etching reaction.

System and method for fabricating photonic device elements

An exemplary mounting structure can be provided for interferometric imaging and an interferometric imaging apparatus comprising same. The mounting structure comprises at least one curved surface for receiving an interferometric grating to rest thereon. The surface can be provided having a plurality of apertures, whereas that the grating when so received, covers at least one of the apertures.

Grid-mounting device for slit-scan differential phase contrast imaging

X-ray scattering imaging can provide complementary information about the unresolved microstructures of a sample. The scattering signal can be accessed with various methods based on coherent illumination, which span from self-imaging to speckle scanning. The directional sensitivity of the existing methods is limited to a few directions on the imaging plane and it requires the scanning of the optical components, or the rotation of either the sample or the imaging setup, if the full range of possible scattering directions is desired. A new arrangement is provided that allows the simultaneous acquisition of the scattering images in all possible directions in a single shot. This is achieved by a specialized phase grating and a device for recording the generated interference fringe with sufficient spatial resolution. The technique decouples the sample dark-field signal with the sample orientation, which can be crucial for medical and industrial applications.

Omnidirectional scattering- and bidirectional phase-sensitivity with single shot grating interferometry

Among the existent X-ray phase-contrast modalities, grating interferometry appears as a promising technique for commercial applications, since it is compatible with conventional X-ray tubes. However, since applications such as medical imaging and homeland security demand covering a considerable field of view, the fabrication of challenging and expensive large-area gratings would be needed. A scanning setup is a good solution, because it uses cheaper line detectors instead of large-area 2D detectors and would require smaller gratings. In this setup, the phase-retrieval using the conventional phase-stepping approach would be slow, so having a faster method to record the signals becomes fundamental. To tackle this problem, a scanning-mode grating interferometer configuration is used, in which a grating is tilted to form Moire fringes perpendicular to the grating lines. The sample is then translated along the fringes, so each line detector records a different phase step for each slice of the sample.

Tilted-grating approach for scanning-mode X-ray grating interferometry

The latest progresses in breast imaging using differential phase contrast techniques pose the question of how to fuse multiple information sources, yielded by absorption, differential phase, and scattering signals, into a single, informative image for clinical diagnosis. It is proposed to use an image fusion scheme based on a multiple-resolution framework. The three signals are first transformed into multiple bands presenting information at different frequencies and then a two-step processing follows: (1) intra-band processing enhances the local signal-to-noise ratio using a novel noise estimation method and context modeling; and (2) inter-band processing weights each band by considering their characteristics and contributions, and suppressing the global noise level. The fused image, looking similar to a conventional mammogram but with significantly enhanced detail features, is reconstructed by inverse transform. The fused image is compatible with clinical settings and enables the radiologists to use their years of diagnosis experiences in mammography.

Image fusion scheme for differential phase contrast imaging

A quantitative radiographic method uses X-ray imaging. The method uses a ratio of the absorption signal and the (small-angle) scattering signal (or vice-versa) of the object as a signature for the materials. The ratio image (dubbed R image) is independent from the thickness of the object in a wide sense, and therefore can be used to discriminate materials in a radiographic approach. This can be applied to imaging systems, which can record these two signals from the underlying object (for instance, an X-ray grating interferometer). Possible applications could be in material science, non-destructive testing and medical imaging. Specifically, the method can be used to estimate a volumetric breast density. The use of the R image and the corresponding algorithm are also presented hereafter.

Quantitative X-ray radiology using the absorption and scattering information

A non-invasive method distinguishes between two types of micro-calcification by x-ray imaging in mammography. Two major types of micro-calcifications are found and confirmed by histopathology and they are correlated to benign and malignant breast lesions. Distinguishing between them non-invasively will significantly improve early breast cancer diagnosis. This is based on the fact that these two types of micro-calcifications show opposite absorption and small-angle scattering signals in x-ray imaging. The imaging system, which can record these two signals of the breast tissue simultaneously for instance, an x-ray grating interferometer, can be used to uniquely determine the micro-calcification type. This is expected to be used in mammography to improve early breast cancer diagnosis, increase diagnosis accuracy and decrease the biopsy rate.

System for non-invasive classification of different types of micro-calcifications in human tissue

An image fusion method combines absorption, differential phase contrast and dark-field (scattering) signals obtained with X-ray phase contrast sensitive techniques, such as an arrangement of gratings. The process fuses the absorption and dark-field signals by principal component analysis. Further the differential phase contrast is merged into the PCA fused image to obtain an edge enhancement effect. Due to its general applicability and its simplicity in usage, the proposed process is usable as a standard method for image fusion scheme using phase contrast imaging, in particular on medical scanners (for instance mammography), inspection at industrial production lines, non-destructive testing, and homeland security.

Method for image fusion based on principal component analysis

An X-ray arrangement is suitable to record absorption, phase contrast, and dark field images of an object. The visibility of low absorbing specimens is improved and required radiation dose is reduced. The assembly includes an X-ray source; two or more gratings; a position-sensitive detector with spatially modulated detection sensitivity; a recorder for recording the images; an evaluator for evaluating the intensities for each pixel to identify the characteristic of the object for each individual pixel as an absorption and/or a differential phase contrast and/or an x-ray scattering dominated pixel. Images are collected by rotating from 0 to n or 2n either the sample or the assembly. The gratings are produced with planar geometry. The X-rays pass through the gratings parallel to the substrate. The grating structures extend along the X-ray path which determines the phase shift. The attenuation of the X-rays caused by the grating structures is no longer given by the thickness, but by the length of the grating structures.

Method for X-ray phase contrast and dark-field imaging using an arrangement of gratings in planar geometry

Phase sensitive X-ray imaging methods provide substantially increased contrast over conventional absorption based imaging, and therefore new and otherwise inaccessible information. The use of gratings as optical elements in hard X-ray phase imaging overcomes some of the problems impairing the wider use of phase contrast in X-ray radiography and tomography. To separate the phase information from other contributions detected with a grating interferometer, a phase-stepping approach has been considered, which implies the acquisition of multiple radiographic projections. Here, an innovative, highly sensitive X-ray tomographic phase contrast imaging approach is presented based on grating interferometry, which extracts the phase contrast signal without the need of phase stepping. Compared to the existing phase step approach, the main advantage of this new method dubbed 'reverse projection' is the significantly reduced delivered dose, without degradation of the image quality.

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Endingen, Switzerland

Marco Stampanoni