3D spatial distribution of ore mineral phases using high resolution synchrotron micro-computed tomography (μCT) combined with optical microscopy

Ore minerals in dolomites and Graphite Mica Schist (GMS) were studied by synchrotron radiation micro-computed tomography (SR-μCT) and optical microscopy. High resolution μCT images of ore minerals were obtained at Imaging Beamline (BL-4), Indus-2 synchrotron radiation source for the comprehensive volume characterization of minerals. Optical microscopy was used for mineral identification, mineral/rock characterization and quantification of ore mineral assemblages was also confirmed by XRD. 3D images from SR-μCT have shown spatial distribution of major minerals and crystals of different minerals in the volume of samples. The results obtained shows that the GMS and dolomitic hosted rocks mined from region near Udaipur, Rajasthan contains sulfide mineral phases. SR-μCT facilitates visualization of the association of the various metallic minerals with the host rock. The presence of economically important metallic minerals galena, sphalerite and pyrite found in the samples through SR-μCT has implications on exploration and processing of ores.

Development of X-ray CCD camera based X-ray micro-CT system

Availability of microfocus X-ray sources and high resolution X-ray area detectors has made it possible for high resolution microtomography studies to be performed outside the purview of synchrotron. In this paper, we present the work towards the use of an external shutter on a high resolution microtomography system using X-ray CCD camera as a detector. During micro computed tomography experiments, the X-ray source is continuously ON and owing to the readout mechanism of the CCD detector electronics, the detector registers photons reaching it during the read-out period too. This introduces a shadow like pattern in the image known as smear whose direction is defined by the vertical shift register. To resolve this issue, the developed system has been incorporated with a synchronized shutter just in front of the X-ray source. This is positioned in the X-ray beam path during the image readout period and out of the beam path during the image acquisition period. This technique has resulted in improved data quality and hence the same is reflected in the reconstructed images.

Synchrotron-based phase-sensitive imaging of leaves grown from magneto-primed seeds of soybean

Experiments were conducted to study the effects of static magnetic fields (SMFs) on the venation network of soybean leaves using the synchrotron-based X-ray micro-imaging technique. The seeds of soybean (Glycine max, variety JS-335) were pretreated with different SMFs from 50 to 300 mT in steps of 50 mT for 1 h. The phase-contrast images obtained showed that, as the strength of the SMF increased, the area, width of the midrib, area of the midrib and minor vein of the middle leaflets of third trifoliate leaves also increased up to the SMF strength of 200 mT (1 h) and decreased thereafter. Quantification of the major conducting vein also showed the differences in the major and minor vein structures of the soybean leaves as compared with control leaves. Further, the phase-retrieval technique has been applied to make the segmentation process easy and to quantify the major and minor veins in the venation network. The width and area of midrib enhancement by pre-treatment with SMF implies an enhancement in the uptake of water, which in turn causes an increased rate of photosynthesis and stomatal conductance.

Synchrotron X-ray phase contrast imaging of leaf venation in soybean (Glycine max) after exclusion of solar UV (280-400 nm) radiation

The hydraulic efficiency of a leaf depends on its vascular structure as this is responsible for transport activities. To investigate the effect of exclusion of UVAB and UVB radiation from the solar spectrum on the micro-structure of leaves of soybean (Glycine max, variety JS-335), a field experiment was conducted using synchrotron-based phase contrast imaging (PCI). Plants were grown in specially designed UV exclusion chambers, and wrapped with filters that excluded UVB (280-315 nm) or UVAB (280-400 nm), or transmitted all the ambient solar UV (280-400 nm) radiation (filter control). Qualitative observation of high-resolution X-ray PCI images obtained at 10 keV has shown the differences in major and minor vein structures of the leaves. The mid-rib width of the middle leaflet of third trifoliate leaves, for all treatments, were obtained using quantitative image analysis. The width of the mid-rib of the middle leaflet of third trifoliate leaves of UVB excluded plants was found to be more compared to leaves of filter control plants, which are exposed to ambient UV. The mid-rib or the main conducting vein transports water and sugars to the whole plant; therefore, mid-rib enhancement by the exclusion of solar UV radiation possibly implies enhancement in the leaf area which in turn causes an increased rate of photosynthesis.

Non-destructive evaluation of teeth restored with different composite resins using synchrotron based micro-imaging

BACKGROUND

Application of high resolution synchrotron micro-imaging in microdefects studies of restored dental samples.

OBJECTIVE

The purpose of this study was to identify and compare the defects in restorations done by two different resin systems on teeth samples using synchrotron based micro-imaging techniques namely Phase Contrast Imaging (PCI) and micro-computed tomography (MCT). With this aim acquired image quality was also compared with routinely used RVG (Radiovisiograph).

METHODS

Crowns of human teeth samples were fractured mechanically involving only enamel and dentin, without exposure of pulp chamber and were divided into two groups depending on the restorative composite materials used. Group A samples were restored using a submicron Hybrid composite material and Group B samples were restored using a Nano-Hybrid restorative composite material. Synchrotron based PCI and MCT was performed with the aim of visualization of tooth structure, composite resin and their interface.

RESULTS

The quantitative and qualitative comparison of phase contrast and absorption contrast images along with MCT on the restored teeth samples shows comparatively large number of voids in Group A samples.

CONCLUSIONS

Quality assessment of dental restorations using synchrotron based micro-imaging suggests Nano-Hybrid resin restorations (Group B) are better than Group A.