xray micro tomography print
TRANSCRIPT
-
8/3/2019 Xray Micro Tomography Print
1/33
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
-
8/3/2019 Xray Micro Tomography Print
2/33
130 million tons/yearworldwide productionof synthetic plastics by
the end of the 20thcentury (Fomin, 2001)
30% annual increase indemand ofbiodegradable plastics(Leaversuch, 2002)
-
8/3/2019 Xray Micro Tomography Print
3/33
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
-
8/3/2019 Xray Micro Tomography Print
4/33
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.
-
8/3/2019 Xray Micro Tomography Print
5/33
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.
-
8/3/2019 Xray Micro Tomography Print
6/33
-
8/3/2019 Xray Micro Tomography Print
7/33
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.
-
8/3/2019 Xray Micro Tomography Print
8/33
-
8/3/2019 Xray Micro Tomography Print
9/33
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).
-
8/3/2019 Xray Micro Tomography Print
10/33
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).
-
8/3/2019 Xray Micro Tomography Print
11/33
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.
-
8/3/2019 Xray Micro Tomography Print
12/33
-
8/3/2019 Xray Micro Tomography Print
13/33
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
-
8/3/2019 Xray Micro Tomography Print
14/33
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
-
8/3/2019 Xray Micro Tomography Print
15/33
AbsorptionPhase
X-ray FlourescenceBest mode will depend upon sample
characteristics (size, chemical
composition, concentration, radiationhardness, etc.)
-
8/3/2019 Xray Micro Tomography Print
16/33
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.
-
8/3/2019 Xray Micro Tomography Print
17/33
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.
-
8/3/2019 Xray Micro Tomography Print
18/33
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.
-
8/3/2019 Xray Micro Tomography Print
19/33
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.
-
8/3/2019 Xray Micro Tomography Print
20/33
-
8/3/2019 Xray Micro Tomography Print
21/33
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.
-
8/3/2019 Xray Micro Tomography Print
22/33
-
8/3/2019 Xray Micro Tomography Print
23/33
-
8/3/2019 Xray Micro Tomography Print
24/33
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.
-
8/3/2019 Xray Micro Tomography Print
25/33
The macroporenetwork is veryhighly
interconnectedand is very similarto the XMT imageof trabecular bone.The pore shape
and size appear tobe veryhomogeneous.
-
8/3/2019 Xray Micro Tomography Print
26/33
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.
-
8/3/2019 Xray Micro Tomography Print
27/33
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.
-
8/3/2019 Xray Micro Tomography Print
28/33
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.
-
8/3/2019 Xray Micro Tomography Print
29/33
-
8/3/2019 Xray Micro Tomography Print
30/33
-
8/3/2019 Xray Micro Tomography Print
31/33
-
8/3/2019 Xray Micro Tomography Print
32/33
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.
-
8/3/2019 Xray Micro Tomography Print
33/33
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.