Spherical acquisition trajectories for X-ray computed tomography with a robotic sample holder

This work presents methods for the seamless execution of arbitrary spherical trajectories with a seven-degree-of-freedom robotic arm as a sample holder. The sample holder is integrated into an existing X-ray computed tomography setup. We optimized the path planning and robot control algorithms for the seamless execution of spherical trajectories. A precision-manufactured sample holder part is attached to the robotic arm for the calibration procedure. Different designs of this part are tested and compared to each other for optimal coverage of trajectories and reconstruction image quality. We present experimental results with the robotic sample holder where a sample measurement on a spherical trajectory achieves improved reconstruction quality compared to a conventional circular trajectory. Our results demonstrate the superiority of the discussed system as it outperforms single-axis systems by reaching nearly 82\% of all possible rotations. The proposed system is a step towards higher image reconstruction quality in flexible X-ray CT systems. It will enable reduced scan times and radiation dose exposure with task-specific trajectories in the future, as it can capture information from various sample angles

Ptychography & lensless X-ray imaging

If an object is illuminated with coherent electromagnetic radiation, e.g., by visible laser light or highly brilliant x-rays, a diffraction pattern is formed in the Fraunhofer far field that is related via a Fourier transform to the optical transmission function of the object.The aim of coherent diffractive imaging (CDI), or so-called lensless imaging, is to directly reconstruct the original optical transmission function of the specimen from its measured diffraction pattern. In principle, CDI allows one to obtain a resolution that is ultimately limited only by the wavelength of the radiation used and not by the quality of optical lenses. In xray microscopy, for instance, the resolution is presently limited to several tens of nanometres because of difficulties in manufacturing efficient high-quality nano-structured x-ray optical elements. Since CDI schemes allow the resolution to be increased beyond these limits they are among the most promising techniques for x-ray imaging applications in life and materials sciences on the nanometre scale

Dose-compatible grating-based phase-contrast mammography on mastectomy specimens using a compact synchrotron source

With the introduction of screening mammography, the mortality rate of breast cancer has been reduced throughout the last decades. However, many women undergo unnecessary subsequent examinations due to inconclusive diagnoses from mammography. Two pathways appear especially promising to reduce the number of false-positive diagnoses. In a clinical study, mammography using synchrotron radiation was able to clarify the diagnosis in the majority of inconclusive cases. The second highly valued approach focuses on the application of phase-sensitive techniques such as grating-based phasecontrast and dark-field imaging. Feasibility studies have demonstrated a promising enhancement of diagnostic content, but suffer from dose concerns. Here we present dose-compatible grating-based phase-contrast and dark-field images as well as conventional absorption images acquired with monochromatic x-rays from a compact synchrotron source based on inverse Compton scattering. Images of freshly dissected mastectomy specimens show improved diagnostic content over ex-vivo clinical mammography images at lower or equal dose. We demonstrate increased contrast-to-noise ratio for monochromatic over clinical images for a well-defined phantom. Compact synchrotron sources could potentially serve as a clinical second level examination

Probe retrieval in ptychographic coherent diffractive imaging

Ptychography is a coherent diffractive imaging method that uses multiple diffraction patterns obtained through the scan of a localized illumination on the specimen. Until recently, reconstruction algorithms for ptychographic datasets needed the a priori knowledge of the incident illumination. A new reconstruction procedure that retrieves both the specimen's image and the illumination profile was recently demonstrated with hard X-ray data. We present here the algorithm in greater details and illustrate its practical applicability with a visible light dataset. Improvements in the quality of the reconstruction are shown and compared to previous reconstruction techniques. Implications for future applications with other types of radiation are discussed. \ua9 2009 Elsevier B.V. All rights reserved

Quantitative phase contrast optimised cancerous cell differentiation via ptychography

This paper shows that visible-light ptychography can be used to distinguish quantitatively between healthy and tumorous unstained cells. Advantages of ptychography in comparison to conventional phase-sensitive imaging techniques are highlighted. A novel procedure to automatically refocus ptychographic reconstructions is also presented, which improves quantitative analysis

Uso de la radiación solar (UV-A y temperatura) en la inactivación del Vibrio cholerae en agua para consumo humano. Factores que condicionan la eficiencia del proceso

Se inoculó Vibrio cholerae en botellas de vidrio, en botellas de plástico y en bolsas plásticas que contenían agua; se expusieron al sol durante 6 horas y se midió la temperatura y la radiación UV-A. Al alcanzar 30°, 35°, 40° y 45° C se tomaron muestras para determinar el nivel de los vibrios y de los coliformes termotolerantes. Se determinaron los impactos de temperatura, turbiedad, recipiente y concentración de los vibrios. Esta bacteria se logró inactivar al alcanzar gradualmente 45° C y 6 horas de exposición al sol; con temperatura constante de 30° C se necesitaron 100 Wh/m2; y con 50° C sólo 10 Wh/m2. La turbiedad es un factor que interfiere con el proceso de SODIS; con 40 UNT se necesitaron 105 Wh/ m2, con 23 UNT, 91 Wh/m2 y con 5 UNT, 36 Wh/m2 de UV-A para lograr 100% de mortalidad. No se encontraron diferencias con el tipo de recipiente usado, siempre se logró 100% de inactivación; tampoco se observaron diferencias en la inactivación con diferentes concentraciones del vibrio. Se lograron altas correlaciones entre la inactivación de coliformes termotolerantes y vibrios (0.86 y 0.99). Vibrio cholerae was inoculated in plastic and glass bottles and plastic bags. The containers were exposed to sunlight during six hours. When temperature raised up to 30° C, 35° C, 40° C, and 45° C, samples of water were taken. The impact of: a) temperature, b) turbidity, c) container and d) initial concentration of vibrio were determined. The bacteria were inactivated with only temperature, when it raised up to 45º C, whereas, with constant temperature of 30º C it was necessary 100 Wh/m2 of the radiation and at 50º C, only 10 Wh/m2. The turbidity caused interference with SODIS process: total inactivation was achieved with different levels: 105 Wh/m2(40 TNU), 91 Wh/m2 (23 TNU) and 36 Wh/m2 (5 TNU). The container type and initial different concentration of vibrio did not have influence on the SODIS process. Full correlation among thermotolerant coliforms and V. cholerae inactivation was always high (0.86 and 0.99)

High-resolution scanning X-ray diffraction microscopy

Coherent diffractive imaging (CDI) and scanning transmission x-ray microscopy (STXM) are two popular microscopy techniques that have evolved quite independently. CDI promises to reach resolutions below 10 nanometers, but the reconstruction procedures put stringent requirements on data quality and sample preparation. In contrast, STXM features straightforward data analysis, but its resolution is limited by the spot size on the specimen. We demonstrate a ptychographic imaging method that bridges the gap between CDI and STXM by measuring complete diffraction patterns at each point of a STXM scan. The high penetration power of x-rays in combination with the high spatial resolution will allow investigation of a wide range of complex mesoscopic life and material science specimens, such as embedded semiconductor devices or cellular networks

Intelligente Druckluftsysteme und Datenmodellierung: Konzeption eines Anwendungsfalls nach ISO 20140

This paper introduces a schemata for the classification of compressed air system components. It presents the standard ISO 20140 as a standardized data modeling technique. The standard represents a method for evaluating energy efficiency and other factors influencing the environment of manufacturing systems. The presented use case is a pneumatic sub system of a smart compressed air system demonstrator

Contrast mechanisms in scanning transmission x-ray microscopy

We present a derivation of the main contrast mechanisms accessible in scanning transmission x-ray microscopy with a pixel-array detector. We consider the effect of the probe defocus and show that it can produce strong differential absorption contrast. The effect of noise is derived and used to compare the relative merits of absorption and differential contrast imaging in various experimental conditions. We illustrate the main results with an experiment that combines a through-focus series with the near-edge signal of a cerium oxide sample. The measurements are seen to follow closely the derived contrast expressions, including the defocus-dependent differential absorption contrast. The analysis includes additional considerations about the application of principal component analysis on a through-focus image series. \ua9 2009 The American Physical Society

Coherent laser scanning diffraction microscopy

Coherent diffractive imaging (CDI) is a promising approach to high-resolution x-ray microscopy. While CDI typically has a rather limited field of view, this problem can be solved by ptychography, a technique for which an extended object is raster scanned by a compact coherent illumination probe. Significant overlap of illumination for adjacent scan points allows then a self-consistent reconstruction from the entirety of collected coherent diffraction patterns. However, current reconstruction schemes require accurate a priori knowledge of the probe. Our recently developed new algorithm for ptychographic data sets allows us to simultaneously reconstruct both object and illuminating probe. We demonstrate the application of the new method in a test experiment with visible laser light showing that intricate illumination functions can be retrieved reliably. \ua9 2009 IOP Publishing Ltd