3D imaging of microstructure of spruce wood.

Synchrotron radiation phase-contrast X-ray tomographic microscopy (srPCXTM) was applied to observation and identification of the features of spruce anatomy at the cellular lengthscale. The pilot experiments presented in the paper clearly revealed the features of the heartwood of Spruce (Picea abies [L.] Karst.), such as lumina and pits connecting the lumina, with a theoretical voxel size of 0.7 x 0.7 x 0.7 microm(3). The experiments were carried out on microspecimens of heartwood, measuring approximately 200 by 200 micrometers in cross-section. The technique for production and preparation of wood microsamples was developed within the framework of this investigation. The total porosity of the samples was derived and the values of the microstructural parameters, such as the diameters of tracheid, cell wall thicknesses and pit diameters were assessed non-invasively. Microstructural features as thin/small as approximately 1.5 microm were revealed and reconstructed in 3D. It is suggested that the position of sub-voxel-sized features (such as position of tori in the bordered pit pairs) can be determined indirectly using watershed segmentation. Moreover, the paper discusses the practical issues connected with a pipelined phase-contrast synchrotron-based microtomography experiment and the possible future potentials of this technique in the domain of wood science.

Implementation of a fast method for high resolution phase contrast tomography.

We report the implementation of a method which can yield the 3D distribution of the phase (refractive index) of a weakly absorbing object from a single tomographic data set. In order to reduce the residual absorption artifact (due to the fact that only one data set is used) the original algorithm presented by A. V. Bronnikov is amended by adding in the filter a factor found by using a semi empirical approach. The quality of the reconstruction is largely sufficient for optimal segmentation and further postprocessing even though the filter correction is based on assumption of constant absorption. This one step approach allows keeping radiation dose to the minimum. Spatial resolution is comparable to the conventional absorption based technique. The performance of the method is validated by using an established phase contrast technique.

Imaging cells and tissues with refractive index radiology.

Can individual cells, including live cells, be imaged using hard x rays? Common wisdom until now required sophisticated staining techniques for this task. We show instead that individual cells and cell details can be detected in culture solution and tissues with no staining and no other contrast-enhancing preparation. The sample examined can be much thicker than for many other microscopy techniques without sacrificing the capability to resolve cells. The key factor in our approach is the use of a coherent synchrotron source and of contrast mechanisms based on the refractive index. The first successful tests were conducted on a variety of cell systems including skin and internal leaf cells, mouse neurons, rabbit fibroblast cells, and human tumor cells.

Synchrotron microangiography with no contrast agent.

Coherent x-rays from synchrotron sources are increasingly used in non-conventional radiological techniques ('phase-contrast' radiology). Our experiments demonstrate that by using white (unmonochromatic) radiation and a time-resolving system, it is possible to image microscopic details of moving blood vessels in different live animals without using any contrast agent. The images have excellent contrast plus unprecedented spatial resolution for microangiography (< 10 microm). This result is likely to impact many different areas of biological and medical research and of diagnostic radiology.

Electrochemistry: building on bubbles in metal electrodeposition.

In the electrodeposition of metals, a widely used industrial technique, bubbles of gas generated near the cathode can adversely affect the quality of the metal coating. Here we use phase-contrast radiology with synchrotron radiation to witness directly and in real time the accumulation of zinc on hydrogen bubbles. This process explains the origin of the bubble-shaped defects that are common in electrodeposited coatings.