Felix Beckmann

3D computed X-ray tomography of human cancellous bone at 8 μm spatial and 10−4 energy resolution

Human cancellous bone was imaged and its absorptive density accurately measured in three dimensions (3D), nondestructively and at high spatial resolution by means of computerized microtomography (microCT). Essential for achieving the resolution and accuracy was the use of monoenergetic synchrotron radiation (SR) which avoided beam hardening effects, secured excellent contrast conditions including the option of energy-modulated contrast, and yet provided high intensity. To verify the resolution, we selected objects of approximately 8 micron size that could be observed on tomograms and correlated them in a unique manner to their counter images seen in histological sections prepared from the same specimen volume. Thus we have shown that the resolution expected from the voxel size of 8 microns used in the microCT process is in effect also attained in our results. In achieving the present results no X-ray-optical magnification was used. From microCT studies of composites (Bonse et al., X-ray tomographic microscopy (XTM) applied to carbon-fibre composites. In: Materlik G, ed. HASYLAB Jahresbericht 1990. Hamburg: DESY, 1990; 567-568) we know that by including X-ray magnification a resolution below 2 microns is obtained. Therefore, with foreseeable development of our microCT method, the 3D and nondestructive investigation of structures in mineralized bone on the 2 micron level is feasible. For example, it should be possible to study tomographically the 3D distribution and amount of osteoclastic resorption in the surrounding bone structure.

X-ray Microtomography (μct) Using Phase Contrast for the Investigation of Organic Matter

PURPOSEnWe show that microtomography (microCT) using synchrotron radiation (SR) can be extended to include X-ray phase contrast, which is two to three orders of magnitude more sensitive than conventional attenuation contrast and better suited for the investigation of specimens consisting chiefly of light elements for photon energies ranging at least from 1 to 100 keV.nnnMETHODnPhase contrast is generated by placing the specimen in one of the interfering beams of an X-ray interferometer. With use of 12-keV X-rays, phase projections of the specimen are recorded at 180 or 360 angular settings equally spaced between 0 and 180 degrees. One phase projection consists of four pairs of associated radiograms in the sense that one is taken with and the other without the specimen in the beam. Between pairs a parallel-sided phase-shifter plate is rotated for changing the relative phase of the two interfering beams by multiples of pi/2 rad. By calculating phase-weighted sums of all associated pairs of radiograms, true phase-shift projections are obtained for all angular settings of the specimen, which are then reconstructed.nnnRESULTSnThree-dimensional images have been obtained from rat cerebrum and rat trigeminal nerve, showing cell structures at 8- to 15-micron spatial resolution. Gray and white matter of cerebrum and neurons in the trigeminal nerve are clearly visible.nnnCONCLUSIONnX-ray phase-contrast microCT is becoming a valuable tool for studies of organic samples in medicine and biology.

New developments in attenuation and phase-contrast microtomography using synchrotron radiation with low and high photon energies

Microtomography using synchrotron radiation is widely used in fields of e.g. medicine, biology and material science. Using attenuation contrast at photon energies in the range of 8 to 25 keV and phase contrast at photon energies of 12 keV, 20 keV and 24 keV the method of microtomography is applied to a large number of samples. A comparison of the two different contrast mechanism is presented. Feasibility, advantage and limits of these methods are shown in theory and by experiment. New developments in high-energy microtomography using synchrotron radiation in the energy range of 60 to 100 keV are described. Using attenuation contrast, several samples are investigated. For the investigation of larger specimens with diameters on the order of 1 - 2 cm, the use of a new (mu) CT-technique based on scanning a 2-dim. X-ray detector is demonstrated. At 70 keV photon energy an X-ray LLL-interferometer is tested and used to measure phase projections. For the first time, phase- contrast microtomography could be applied to weakly and normally absorbing material at a high photon energy.

Phase-contrast x-ray tomography using synchrotron radiation

The principle and experimental l realization of x-ray phase- contrast in compute assisted microtomography ((mu) CT) at the micrometer resolution level is described. The camera used is a modification of a setup previously developed by us for attenuation-contrast (mu) CT using synchrotron x-rays. Phase detection is accomplished by employing the x-ray interferometer. By using x-ray phase contrast it is possible to image structural details in low-z biological tissues much better than with absorption contrast. The advantage of phase over attenuation contrast is not limited to light element or to low x-ray energies. Examples of applying phase contrast (mu) CT to the structural investigation of rat trigeminal nerve are given.

Microtomography using synchrotron radiation at DESY: current status and future developments

The X-ray microtomography system which is operated at the Hamburger Synchrotronstrahlungslabor HASYLAB of the Deutsches Elektronen-Synchrotron DESY in Hamburg, Germany, is presented. At the DORIS storage ring synchrotron radiation at the wiggler beamlines BW2, W2, and BW5 was used to run the microtomography apparatus as a user experiment. The development of tomography scanning techniques to investigate samples which are larger than the field of view of the X-ray detector is demonstrated for dental implants using the photon energy of 90 keV at the high energy beamline BW5. In cooperation with DESY the GKSS Research Center is setting up the high energy beamline HARWI-2 at the DORIS storage ring of DESY. This beamline will allow for tomography experiments using monochromatic X-rays from 20 to 200 keV with a beam size of 70•10 mm2. Furthermore the GKSS is operating a neutron radiography facility GENRA at the research reactor Geesthacht FRG, Geesthacht, Germany. It is intended to extend this facility by a tomography station. The combination of synchrotron radiation based microtomography with neutron tomography will allow for the development of new techniques to give new insight in the 3-dim. behavior of samples especially in materials science.

Multiple-beam X-ray interferometry for phase-contrast microtomography

The first successful operation of an X-ray interferometer under conditions of non-planar three-beam diffraction for phase-contrast X-ray microtomography is reported. Intrinsic phase differences of the reflections used cancel from the three-dimensional phase image of the specimen. With simultaneous hkl and hkl reflections of a synchrotron radiation beam in a side-by-side geometry, the size of the usable field of view is doubled and the investigated specimen volume is increased by a factor of four. As an example, the reconstructed slice of a mouse kidney is shown in phase contrast at 71 keV. Optimized choices of three-beam reflections and matching interferometer geometries useful for applications are presented.

The New Materials Science Beamline HARWI‐II at DESY

In autumn 2005, the GKSS‐Research Center Geesthacht in cooperation with Deutsches Elektronen‐Synchrotron DESY, Hamburg, started operation of the new synchrotron radiation beamline HARWI‐II. The beamline is specialized for performing materials science experiments using hard X‐rays. First experiments were successfully performed studying the residual strain in a VPPA welded Al alloy plate, the texture of cold extruded Al90‐Cu10 composites, and the 3 dimensional material flow of friction steer welds by micro tomography. At the new beamline HARWI‐II, the GKSS now has direct access for using synchrotron radiation for materials science experiments.

Neue Möglichkeiten der Strukturanalyse von Knochenbiopsien bei Anwendung der Mikrocomputertomographie (μCT)

ZusammenfassungEs wird die kombinierte Anwendung und quantitative Auswertung 2dimensionaler histologischer Schnitte sowie 2- und 3dimensionaler Mikrotomogramme zur Analyse der Knochenstruktur in Knochenbiopsien beschrieben. Gegenüber dem sehr zeitaufwendigen Verfahren der 3dimensionalen Rekonstruktion aus histologischen Schnitten ist die Mikrotomographie (μCT) schnell genug, um für Routineuntersuchungen in Frage zu kommen. Überdies arbeitet die μCT zerstörungsfrei und vermeidet Schnittartefakte. Art und Ausmaß krankheitsbedingter Spongiosaveränderungen können anhand der 3 D-Tomogramme, dank ihrer hohen Ortsauflösung von rund 10 μm, sehr exakt dargestellt werden. Besonders in Knochenbiopsien mit einer Reduktion der Spongiosastruktur wird das Ausmaß der Strukturveränderungen 3dimensional wesentlich deutlicher als im 2dimensionalen Schnittpräparat. Das Verfahren stellt ein wichtiges Bindeglied zwischen nichtinvasiv erhobenen Strukturdaten und histologischen Veränderungen dar.SummaryThe combined histological and microcomputed analysis of human iliac crest biopsies leads to major advances in our understanding of three-dimensional bone architecture. Microcomputed tomography avoids the time-consuming reconstruction and artifacts of serial sections. Furthermore, its high resolution allows the recording of structural differences as low as 10 mm. Thus, three-dimensional analysis in combination with histological evaluation of cellular dynamics facilitates earlier and easier recording of changes of cancellous bone.

Micro-CT at the imaging beamline P05 at PETRA III

The Imaging Beamline (IBL) P05 is operated by the Helmholtz-Zentrum Geesthacht and located at the DESY storage ring PETRA III. IBL is dedicated to X-ray full field imaging and consists of two experimental end stations. A micro tomography end station equipped for spatial resolutions down to 1u2005µm and a nano tomography end station for spatial resolutions down to 100u2005nm. The micro tomography end station is in user operation since 2013 and offers imaging with absorption contrast, phase enhanced absorption contrast and phase contrast methods. We report here on the current status and developments of the micro tomography end station including technical descriptions and show examples of research performed at P05.

Tomography using monochromatic thermal neutrons with attenuation and phase contrast

Attenuation-contrast tomography with monochromatic thermal neutrons was developed and operated at guide station S18 of the institute Laue-Langevin in Grenoble. From the S18 spectrum the neutron wavelength (lambda) equals 0.18 nm was selected by employing a fore crystal with the silicon 220 reflection at a Bragg angle (Theta) equals 30 degrees. Projections were registered by a position sensitive detector (PSD) consisting of a neutron-to-visible-light converter coupled to a CCD detector. Neutron tomography and its comparison with X-ray tomography is studied. This is of special interest since the cross section for neutron attenuation ((sigma) atom) and the cross section for neutron phase shift (bc) are isotope specific and, in addition, by no means mostly monotonous functions of atomic number Z as are attenuation coefficient ((mu) x) and atomic scattering amplitude (f) in the case of X-rays. Results obtained with n-attenuation tomography will be presented. Possibilities and the setup of an instrument for neutron phase-contrast tomography based on single-crystal neutron interferometry will be described.