Diffraction Enhanced Imaging at the UK Synchrotron Radiation
Source
M.Ibison, K.C.Cheung, K.Siu, C.J.Hall, R.A.Lewis, A. Hufton, S.J.Wilkinson, K.D.Rogers, A.Round
Principal Objectives of DEI Development Activities at the SRS
reduce the proportion of available time spent on alignment, in preparation for useful imaging
increase reliability and stability in mechanics and software, to improve image quality
approach a ‘turn-key’ facility for DEI users without need for expertise in the detailed method.
Also:- obtain useful experience for designing 2nd generation DEI on higher-energy SRS station.
DEI System – Station 7.6• High precision optics required• 2-crystal monochromator and 2-crystal analyser• Si 311 crystals give sharper x-ray extinction• Higher contrast, higher resolution images.
X-Ray Optics Alignment Laser
• red beam ( = 623nm), <1 mW output
• compact (2.5cm x 1cm), power source = 2 x 1.5V batteries
• micrometer adjustments, Vertical & Horizontal angle & displacement
• spot of 2mm x 1mm at working range of 2m
Monochromator and 4-Crystal Alignment using Laser Assistance
Monochromator Alignment Analyser Alignment
NOTE: Vertical Spacing between crystals exaggerated for clarity.
Laser Method for Determination of Motor Drive Calibration Factors
Laser laser
Monochromator crystal cage scale
rotation
deflection
Tangent Arm
Motor Drive
Laser Method for Determination of Motor Drive Calibration Factors
Laser laser
Monochromator crystal cage scale
rotation
deflection
Tangent Arm
Motor Drive
Ionisation Chamber for X-Ray Beam Location
• polymer window (5cm x 1cm)
• thickness = 70m• atmospheric pressure
Silicon p.i.n. PhotoDiodefor DEI Alignment
• Sensitive Area: 3.5mm x 3.5mm
• Thickness (effective): 250m
• Window: 10m Al foil (for 14keV X-rays)
Medical Applications of DEI: Mouse Feet Study
Refraction Images
Normal Diseased
• vertical view• through sole of foot
Absorption Images
Normal Diseased
Mouse Feet Study (2)
Normal Diseased
Refraction
Images
• horizontal view• through side of foot
Absorption Images
Normal Diseased
DEI Insect Studies
Refraction
Image
Absorption
Image
Beetle Earwig
Computerised Tomography – Principles
Examples of CT Reconstruction
Input to Reconstruction = Set of Projections (Sinogram)
Results of Reconstruction = Cross-Section (Slice)
Effect of Filtering on Reconstructed Image
Unfiltered
Filtered
Volume Visualisation
• 3-D Rendering of a Mouse Liver, based on CT dataset (ELETTRA)• Uses Volume/Surface modelling features of software packages
Second-Generation DEI System:Some Design Considerations
higher energy and greater flux (on wiggler Station) - better penetration, lower subject dose
channel-cut crystals - facilitate alignment, reduce drift rigidity and anti-vibration built into support structure mountings optimize use of existing framework - station
sharing remains feasible vacuum enclosure of the monochromator - avoids
convection currents and ozone damage risk cooling provision for the 1st crystal - highest heat loading
from ‘white’ beam.
Acknowledgements
The authors would like to thank:-
Medical Research Council- for funding this research programme
Giuseppe Salvini and Janet Groves (CLRC Daresbury)- design and construction of the p.i.n. diode device
Greg Johnson (CLRC Rutherford Appleton Laboratory)- design and implementation of DSP reconstruction system
Andrew Mather (Liverpool University)- Java implementation of the FBP reconstruction software.
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