Martin Bech

High-resolution brain tumor visualization using three-dimensional x-ray phase contrast tomography

We report on significant advances and new results concerning a recently developed method for grating-based hard x-ray phase tomography. We demonstrate how the soft tissue sensitivity of the technique is increased and show in vitro tomographic images of a tumor bearing rat brain sample, without use of contrast agents. In particular, we observe that the brain tumor and the white and gray brain matter structure in a rats cerebellum are clearly resolved. The results are potentially interesting from a clinical point of view, since a similar approach using three transmission gratings can be implemented with more readily available x-ray sources, such as standard x-ray tubes. Moreover, the results open the way to in vivo experiments in the near future.

Soft-tissue phase-contrast tomography with an x-ray tube source.

We report the first experimental soft-tissue phase-contrast tomography results using a conventional x-ray tube source, with a millimeter-sized focal spot. The setup is based on a Talbot-Lau grating interferometer operated at a mean energy of 28 keV. We present three-dimensional ex vivo images of a chicken heart sample, fixated in formalin. The results clearly demonstrate the advantageous contrast attainable through phase-contrast imaging over conventional attenuation-based approaches.

Hard X-ray phase-contrast imaging with the Compact Light Source based on inverse Compton X-rays

The first imaging results obtained from a small-size synchrotron are reported. The newly developed Compact Light Source produces inverse Compton X-rays at the intersection point of the counter propagating laser and electron beam. The small size of the intersection point gives a highly coherent cone beam with a few milliradian angular divergence and a few percent energy spread. These specifications make the Compact Light Source ideal for a recently developed grating-based differential phase-contrast imaging method.

Multimodal x-ray scatter imaging

We describe a small-angle x-ray scattering-based imaging technique that reveals the distribution and orientation of nano-scale structures over extended areas. By combining two measurement and analysis schemes, complementary structural information is available which renders the technique suitable for a broad range of applications, e.g. in materials science and bio-imaging. Through a combination of current techniques and on-line analysis schemes, measurements with a so far unprecedented combination of speed, dynamic range and point density became feasible. This is illustrated by data recorded for a section of a mouse soleus muscle visualizing fine muscle and Achilles tendon structures down to the 10?nm range over a 10?mm2 sample area.

Directional x-ray dark-field imaging.

We introduce a novel x-ray imaging approach that yields information about the local texture of structures smaller than the image pixel resolution inside an object. The approach is based on a recently developed x-ray dark-field imaging technique, using scattering from sub-micron structures in the sample. We show that the method can be used to determine the local angle and degree of orientation of bone, and fibers in a leaf. As the method is based on the use of a conventional x-ray tube we believe that it can have a great impact on medical diagnostics and non-destructive testing applications.

X-ray dark-field and phase-contrast imaging using a grating interferometer

In this letter, we report results obtained with a recently developed approach for grating-based x-ray dark-field imaging [F. Pfeiffer et al., Nat. Mater. 7, 134 (2008)]. Since the image contrast is formed through the mechanism of small-angle scattering, it provides complementary and otherwise inaccessible structural information about the specimen at the micron and submicron length scales. Our approach is fully compatible with conventional transmission radiography and the grating-based hard x-ray phase-contrast imaging scheme [F. Pfeiffer et al., Nat. Phys. 2, 258 (2006)]. Since it can be used with standard x-ray tube sources, we envisage widespread applications to x-ray medical imaging, industrial nondestructive testing, or security screening.

Molecular X-ray computed tomography of myelin in a rat brain

In this work we demonstrate the feasibility of applying small-angle X-ray scattering computed tomography (SAXS-CT) for non-invasive molecular imaging of myelin sheaths in a rat brain. Our results show that the approach yields information on several quantities, including the relative myelin concentration, its periodicity, the total thickness of the myelin sheaths, and the relative concentration of cytoskeletal neurofilaments. For example the periodicity of the myelin sheaths varied in the range from 17.0 to 18.2 nm around an average of 17.6 (±0.3) nm. We believe that imaging, i.e., spatially resolved measuring these quantities could provide general means for understanding the relation to a number of neurodegenerative diseases.

Advances in the visualization of unstained brain tumors using grating-based x-ray phase-contrast tomography

We report advances and complementary results concerning a recently developed method for high-sensitivity grating-based hard x-ray phase tomography. We demonstrate how the soft tissue sensitivity of the technique can be used to obtain in-vitro tomographic images of a tumor bearing rat brain specimen, without use of contrast agents. In particular, we demonstrate that brain tumors and the white and gray brain matter structure in a rats cerebellum can be resolved by this approach. The findings are potentially interesting from a clinical point of view, since a similar approach using three transmission gratings can be implemented with more readily available x-ray sources, such as standard x-ray tubes. Moreover, open the results the way to in-vivo experiments in the near future.

X-ray vector radiography imaging for biomedical applications

The non-invasive estimation of fracture risk in osteoporosis remains a challenge in the clinical routine and is mainly based on an assessment of bone density by dual X-ray absorption (DXA) although bone micro-architecture is known to play an important role for bone fragility. Here we report on X-ray vector Radiography measurements able to provide a direct bone microstructure diagnostics on human bone samples, which we compare qualitatively and quantitatively with numerical analysis of high resolution radiographs.

Results from the first preclinical CT scanner with grating based phase contrast and a rotating gantry

After successful demonstrations of soft-tissue phase-contrast imaging with grating interferometers at synchrotron radiation sources and at laboratory based x-ray tubes, a first preclinical CT scanner with grating based phase contrast imaging modality has been constructed. The rotating gantry is equipped with a three-grating interferometer, a 50 watt tungsten anode source and a Hamamatsu flat panel detector. The total length of the interferometer is 45 cm, and the bed of the scanner is optimized for mice, with a scanning diameter of 35 mm. From one single scan both phase-contrast and standard attenuation based tomography can be attained, providing an overall gain in image contrast.