xray micro tomography print

8/3/2019 Xray Micro Tomography Print

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Aileen Grace M. OngkikoMSE 225: Principles of X-ray Diffraction and Crystallography

Department of Mining, Metallurgical and Materials EngineeringUniversity of the Philippines Diliman

23 March 2010


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130 million tons/yearworldwide productionof synthetic plastics by

the end of the 20thcentury (Fomin, 2001)

30% annual increase indemand ofbiodegradable plastics(Leaversuch, 2002)


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Polymer materials -- compounds of highmolecular weight (normally organic) thestructure of which is composed of chains of smallrepeat units.

Degradable plastics undergo a significantchange in chemical structure under specificenvironmental conditions (ASTM & ISO)measured by standard methods

Biodegradable plastics undergo degradationfrom the action of naturally occurringmicroorganisms such as bacteria, fungi andalgae


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A three-dimensional imaging technique that uses aseries of radiographic images to reconstruct a mapof an objects x-ray absorption.

It is identical in practice to medical computed axialtomography (CAT) scans, except thatmicrotomography achieves much higher spatialresolution by combining extremely bright,monochromated synchrotron radiation with highquality optics and x-ray detection

Microtomographic scans result in volumetric imageswith possible spatial resolutions approaching onemicron.


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Synchrotron-based microtomography has beenused to study pore structure in a variety ofheterogeneous materials.

The significance of the technique is in its abilityto capture true three-dimensional internalstructure at relatively high resolution.

The images produced by tomographic scans and

subsequent reconstruction are grayscalevolumes where the pixel intensity is roughlyproportional to the objects density.


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The digital data produced by the tomographic scans allows us toemploy an extensive library of image analysis and imageprocessing techniques.

For image segmentation, microtomography produces images

where the voxel intensity is proportional to the density of thematerial at that point in space.

A voxel is a volume element, or a 3D pixel.

For 8-bit images, each voxel takes on a value between 0 and 255.In this case zero is black, corresponding to minimum density, and

255 is white, corresponding to maximum density. A pixel intensity histogram, can be constructed showing the

distribution of pixel intensities in the image.


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Synchrotron radiation refers to an electromagnetic radiationproduced when ultra-relativistic electrons (energies ofseveral GeV) circulating in a storage ring are deviated bystrong magnetic fields.

The storage ring consists of a succession of bendingmagnets and straight sections including insertion devices(wigglers and/or undulators).

The synchrotron light is emitted in a narrow cone, tangent tothe curved trajectory of the electrons in the storage ring.

It has a very high intensity and a continuous spectrum,spanning the whole range from IR (wavelength between 2.5to 25m) to X-rays (wavelength between 0.1 to 3).


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This large range of wavelengths will allowmapping different properties of materials atdifferent scales.

The particularity of synchrotron sources is thebrilliance of the emitted light which is severalorders of magnitude higher than that ofconventional sources (typically on the order of1010).

The brilliance is expressed inphotons/s/mm2/mrad2/0.1% BW (bandwidth).


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3 elements of a synchrtron source: alinearaccelerator or linac, which produces the electrons, acircular accelerator or synchrotron in which electronsare raised to their nominal energy and a storage ring

where they are maintained at a constant energy The storage ring includes different types of magnetsand insertion devices connected to the beamline.

Beamlines are located all around the storage ringand are optimized for a given technique in terms ofinsertion devices (wiggler of undulator), range ofenergy available and beam size at the sample.


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The very high intensity of the X-ray beam,which allows improving the signal to noiseratio (SNR) in the images while reducing

acquisition times as compared to standardmicro-CT

The possibility of a using a monochromaticand tunable energy

Images represent maps of the linearabsorption coefficient within the sample fora given energy


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3D Analysis of Air Void Systems

Assessment of bone mineralization,Provide information on bone ultra-structure, study detailed modifications in bone composition, maturationand effects of treatments

At the nanometer and subnanometer scales, charaterize crystals andmineral particles in terms of their orientation, shape and thickness

For high resolution, 3D digital images of small specimens

3D characterization of microstructure in cell walls of aluminum foams

Rheology analysis of a fibre-reinforced mortar

Simulation of mechanical properties of an aluminum matrix composite


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AbsorptionPhase

X-ray FlourescenceBest mode will depend upon sample

characteristics (size, chemical

composition, concentration, radiationhardness, etc.)


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In absorption-edge SR-CT the attenuation of a fan beam of X-rays passing through thesample under analysis is collected as follows.

1. A scintillator converts the transmitted X-rays into visible light and the resultingabsorption projection is captured by a detector such as a high speed CCD camera.

2. The sample is then rotated, by a small angle, and another image is collected.

3. This process is repeated several times as images are collected between 0 and 180.

4. These images are then reconstructed to develop cross sections of the sample thatallow 3D visualisation.

5. Owing to the tunability of the SR, a set of images can be collected below and abovethe absorption edge of an element of interest and, by subtracting them, it is possibleto obtain a 3D distribution of the element of interest within the sample investigated.

This technique allows the probing of relatively large objects in a reasonable time(exposure time is generally a few sec per image) and with a resolution of a fewmicrometers.

Only possible for samples where the element of interest is rather concentrated.


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Collagen scaffolds: incorporate predefinedinternal channels; obtained with the aid ofsacrificial moulds that have been

manufactured using a rapid prototypingtechnique

A computer aided design file of the mouldwas created and then realised using an ink-

jet printer.A dispersion of collagen was then cast into

the mould and frozen.


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Ethanol was used to dissolve the mould leavingthe collagen, which was then freeze dried toproduce the final product.

Scaffold: analysed using X-ray microtomography(XMT) to determine whether the desired internalstructure was obtained; addittion of saturatedpotassium iodide (KI) solution to the scaffold inorder to analyse it satisfactorily by XMT

The resultant images indicate that the desiredinternal structure was obtained.


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X-ray microtomographic system: HMX-225 radiographyplatform (X-Tek, Tring, UK) run under Tomahawktomography software (AEA Technology, Harwell, UK)

a specimen was placed in the path of X-rays; rotated and

also translated perpendicularly to the X-ray beam

In tomographic imaging, a number of absorption profiles ofthe specimen are captured using a cone projection for acomplete rotation of the sample.

Typically, a radiograph is taken every 0.5. From these data,the 3D image can be reconstructed using a standard filteredback-projection algorithm. The system allows the X-ray

voltage and current to be varied independently.


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describes how the use of hierarchical porous materials intissue engineering applications has the potential to shifttreatments from tissue replacement to tissue regeneration

describes how the structure and properties of the scaffolds

are being optimized with respect to cell response and thattissue culture techniques must be optimized to enablegrowth of new bone in vitro

Bioactive glass foam scaffolds: have a hierarchical porousstructure similar to that of trabecular bone, they can bond to

bone and soft tissue and they release silicon and calciumions that have been found to up-regulate seven families ofgenes in osteogenic cells.


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XMT unit: (Phoenix X-ray Systems and Services GmbH)

XMT unit: based on the same principles as a CAT scan (computed axialtomography) where series of two-dimensional transmission X-ray imagesare reconstructed to form a threedimensional image

Key difference: geometric enlargement is used to magnify the image byplacing the object close to a micron sized spot source, producing amagnified image which is projected onto a solid-state detector a largedistance from the object (relative to the sourceobject distance)

Similarity to CAT scan: it provides quantitative data on the integrateddensity and atomic number of the matter in each voxel (volume pixel)

Reconstructed images consisting of 512x512x512 voxels, each of 4.7 mmon a side, were collected from each sample set and cropped digitally toremove the edge artefacts.


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The macroporenetwork is veryhighly

interconnectedand is very similarto the XMT imageof trabecular bone.The pore shape

and size appear tobe veryhomogeneous.


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an isolated pore that isrepresentative of the entiresample, which is connected toother pores on 46 sides.

Connectivity occurs because

the spherical air bubbles areall in contact with each otherimmediately prior to gelation,separated only by a thin film ofsilica-based sol that isstabilized by the surfactant.

Upon gelation and subsequentthermal processes the thin filmdrains, shrinkage occurs andthe surfactant is combusted,leaving the apertures.


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X-ray micro-tomography: used to uncoverthe complex 3-D micro-architecture of adegradable polymer sponge designed for

bone augmentation.The measurements performed were based

on a synchrotron radiation source resultingin a spatial resolution of about 5.4 mm.

The paper presents the quantitative analysisof the porosity and of the pore architecture.


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Elucidate that synchrotron radiation at the photon energy of 9 keV has anappropriate cross section for this low-weight material

Describe the treatment of the data, an amount of 2.5 Gbyte to generatebinary data

Compare the 3-D with the 2-D analysis in a quantitative manner. The obtained values for the mean distance to material within the sponge

calculated from 2-D and 3-D data of the whole tomogram differsignificantly: 12.5 mm for 3-D and 17.6 mm for 2-D analysis.

If the pores exhibit a spherical shape as frequently found, the derivedmean pore diameter, however, is overestimated only by 6% in the 2-D

image analysis with respect to the 3-D evaluation.

This approach can be applied to different porous biomaterials andcomposites even in a hydrated state close to physiological conditions,where any surface preparation artifact is avoided.


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Bastiolli, C. Handbook of Biodegradable Polymers. 2005. Shropshire, UnitedKingdom.

Belgacem, M. N. and A. Gandini, Ed. 2008. Monomers, Polymers andComposites from Renewable Resources.Elsevier, Great Britain.

Callister, W. D. Jr. Material Science and Engineering: An Introduction. 2007.Techbooks/GTS, York, PA, US.

Flieger, M., M. Kantorova, A. Prell, T. Rezanka & J. Votruba. 2003.Biodegradable plastics from Renewable Sources. Folia Microbiol. vol. 48(1), pp. 27-44.

Kolybaba, M., L.G. Tabil, S. Panigrahi, W. J. Crerar, T.Powell and B. Wang. 2003.

Biodegradable Polymers: Past,Present and Future. ASAE RRV03-0007. St.Joseph, Mich.: ASAE

Landis,E. N. and D. J. Corr. 2006. Three Dimensional Analysis of Air VoidSystems in Concrete. Measuring, Monitoring and Modeling ConcreteProperties. Springer. Pp. 517-524.


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Peyrin, F. 2009. Investigation of bone with synchrtron radiation imaging: from micro to nano.Osteoporos Int., Springer. vol 20, pp. 1057-1063.

Lombi,E. and J. Susini. 2009. Synchrotron-based techniques for plant and soil science:oppurtunities, challenges and future perspectives.Plant Soil, Springer. vol. 320, pp. 1-35.

Muller, B., F. Beckmann, M. Huser, F. Maspero, G. Szekely, K. Ruffieux,P. Thurner,E.Wintermantel. 2002. Non-destructive three-dimensional evaluation of a polymer spongeby micro-tomography using synchrotron radiation.Elsevier Science. pp. 73-78.

Smith,P.J.,E. Sachlos, S. McDonald, N. Reis, B. Derby,P. M. Mummery, J. T. Czernuska. 2003.Characterisation of Collagen Scaffolds using X-ray Microtomography. MaterialsResearch Society Symp.Proc. vol. 758, pp. 5.2.1-5.2.6.

Jones, J. R.,P. D. Lee and L. L. Hench. 2005. Heirarchical porous materials for tissueengineering.Philosophical Transactions of the Royal Society. pp. 236-281.

Venezuela, J.J.D.G. MatE11 Lecture Presentations. 2009.

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