principles marcel meinders - wur.nl · x-ray tomography (xrt) micro computer tomography (μct)...
TRANSCRIPT
X-ray Computer Tomography
Principles
Marcel Meinders
Outline
X-ray Tomography
● Principles of operation
● Comparison with other techniques
● Phoenix v[tome]x m
● Technical possibilities
● Computational facilities
X-ray tomography (XRT)
micro/nano computed tomography (μCT/nCT)
Non-invasively measurement of the 3D structure of objects at spatial resolution below 1 μm
2D shadow images Pixel: X-ray transmission
3D volumetric data : Voxel local density
X-ray tomography (XRT)
micro computer tomography (μCT)
Synchrotron polychromatic or monochromatic beam, parallel beam, resolution <0.5 μm, measurement time ~ 1 min
Lab scale, resolution <1 μm, measurement time > 15 min
● source/detector rotates (medical scanners)
● sample rotates
X-Ray Tomography: principle of operation
X-ray beam polychromatic
X-ray tube
Detector projection images cross sections
Tomographic reconstruction
3D model
sample rotation
Principles tomographic reconstruction
projection
Principles X-ray absorption
X-ray spectrum
V
Material parameter
Lambert Beer law
Filament
electrons
X-ray source
Anode
Bremsstrahlung
Comparison with other (3D) imaging techniques
XRT: a missing complementary technique
Technique Contrast Moisture Complexity Chemical specificity
MRI proton spin high High Moderate
XRT atomic density low Low Low
CLSM fluorescence markers high High High
TEM electron scatter dry High Low
available in Wageningen
1px=0.7m (228x228px2=0.16x0.16mm2)
1px=0.22m (727x727px2=0.16x0.16mm2) ESEM XRT (ESRF)
Electron microscopy bread like system
Gerard van Dalen, Unilever.
CSLM images model bread crusts
Red = protein Green = starch
CSLM CSLM XRT
Fluorescent probes that bind
specifically to a certain element
time: 3.1 13.4hrs
Spin Echo
~ 4 cm
~ 3 cm
Single Point Imaging
Magnetic Resonance Imaging
Experimental parameters: matrix 64x64x10; FOV 40x40 mm; TR 10ms; TD = 0.125 ms; 8 averages;
resolution 0.625 mm; total scan time:54m36s800ms
WUR X-ray tomography facility
CAT-AgroFood microCT centre operational since April 2013
● XRT Phoenix v[tome]x m GE
● Two X-ray sources
High Resolution (≥ 0.8 μm)
Large Sample Size (40cm/50kg)
Broad range of applications
● structure-function relations
● Foods, bio-based materials
● soil, roots,
● plants, seeds,
● insects , ….
Technical characteristics lab scale scanner
Spatial resolution / magnification (below 1 μm)
Low acquisition time (down to minute scale)
Good contrast and signal to noise ratio
Broad sample size/material range (from 1 mm up to 40 cm and 50 kg
Cone beam
X-ray sources
Two X-ray sources
● Reflection target (200kV/200W)
● high flux, small spot size
● strongly absorbing materials
● large sample size
● Transmission target (100kV/10W)
● low flux, tiny spot size
● soft materials
● small sample size
● Easy changeable
Resolution v[tome]x m
microfocus head / reflection target (5 and 3-4 μm)
(depends on direction due to elipsoidal shape source/target)
nanofocus head / transmission target (0.8 μm)
Computing facilities
• Dedicated high performance
workstations with maximal graphic
power and memory
• Fast tomography reconstruction
software with special correction
algorithms.
• State of the art software for
visualisation, image analysis,
meshing, and modeling.
Applications….