Transcript Mark Ibison Liverpool University and CLRC Daresbury Laboratory

Progress in medical Diffraction Enhanced Imaging at the UK Synchrotron Radiation Source
C. J.
a CCLRC
a
Hall ;
M.
b
Ibison ;
K. C.
a
Cheung ;
K. K. W.
d
Siu ,
d
Lewis ; A.
e
Hufton ;
c
Wilkinson ;
R. A.
S. J.
K. D.
Flahertya, B. Dobsona; M. Rowleyd; A. Cookf
c
Rogers ; A.
c
Round ;
K.
a
Fayz ,
D.
a
Laundy .
J.
Daresbury Laboratory, UK; b Liverpool University, Liverpool, UK; c Cranfield University, Shrivenham, UK; d Monash University, Melbourne, Australia; e Christie Hospital,
Manchester, UK; f University of Melbourne, Australia
Introduction
This work is supported by EEC contract: CT-1999-50008, and the UK Medical Research Council. Grant: 62861
Diffraction Enhanced Imaging (DEI) is an x-ray phase contrast technique which shows great promise for a number of medical imaging problems. The source is a highly collimated flux of
monochromatic x-rays, currently only available as synchrotron radiation. Phase shifts occurring as the wave passes through the object are made visible using Bragg diffraction from a post-sample
analyser optic. In early 2004 the DEI system on the bending-magnet beam line 7.6 of the Daresbury SRS was used for the first time to image small medical specimens. The performance of the
system and the results of these initial studies are presented.
A new DEI instrument is currently in the design phase. This will be integrated on SRS wiggler station 9.4 allowing shorter x-ray wavelengths and greater flux. Progress on the design and
implementation of this system is reported.
DEI Alignment
DEI Camera at SRS
DEI Applications - Results
Axial View
Sagittal View
Arthritis
Study
of
Mouse
For DEI, a high precision
A small laser on a
Feet
x-ray diffraction optical
micrometer mount is
used
for
initial
alignment of the x-ray
optics. It is also useful
for the calibration of
crystal motor drives in
steps/degree.
arrangement is required.
The SRS camera design
consists of a double-crystal
monochromator and a
double-crystal
analyser.
Si311 crystal planes are
used to give a sharper xray extinction function
(‘rocking-curve’) for better
contrast
and
higher
resolution images.
DEI System Schematic
Package:
8mm dia x 4mm
depth
Active area:
3.5mm x 3.5mm
DEI exploits the refractive nature of x-rays to
identify the boundaries between different media
even if their x-ray attenuations are very similar. The
highly- collimated synchrotron light source is ideal
for this work.
diseased
Absorption images
Swelling characteristic of the
condition is clearly visible.
Damage to the cartilage of the
joints is less obvious, but may
be discerned in the refraction
images.
Current
Amplifier
Data
Logger
Analyser - filters
refraction from
absorption.
normal
A DEI study of the feet of a
susceptible strain of mouse
aimed to investigate evidence
for articular cartilage damage
(osteoarthritis), particularly in
the toe joints.. Two excised feet,
one normal, the other with
advanced
arthritis,
were
compared.
Use of p.i.n. Diode as Alignment Detector
X-ray Beam
Monochromator - removes
unwanted dispersion and
provides single energy beam.
5mm
Refraction images
Design for New DEI System (Summer 2005)
V to F
Converter
Framework and Motors
for Crystal Mounting,
SRS Station 9.4
Ratemeter
Identical Monochromator
and Analyser Crystals are
secured to the motor
500mm
shafts
Window: 10mm Al foil (opaque to visible light)
Intrinsic efficiency: ~ 50% (14keV)
Possible Future Applications:
•Medical/Biological
- mammography; cartilage; osteoporosis;
sport/veterinary
•Materials and NDT
- voids/bubbles in low-density samples
•Chemistry: Reaction Studies
- crystal formation in products, solid phase
Channel-cut Crystal (with water cooling on
1st crystal taking ‘white’ X-ray beam)
Design Improvements:
 higher energy (40keV optimum), greater flux -> better penetration, lower
subject dose;
 channel-cuts eliminate relative alignment of 2 crystals in a pair, so exactly
parallel -> greatly reduced drift;
 greater rigidity & anti-vibration in supports, including advanced airbearing technology;
 maximum use of existing mounts -> enable station sharing without
demounting optics;
 vacuum enclosure of monochromator -> avoids convection currents and
ozone damage;
 cooling provided on 1st (monochromator) crystal (see diagram)
Mark Ibison
Liverpool University and CLRC
Daresbury Laboratory
Warrington, Cheshire, WA4 4AD, UK
Email: [email protected]
Tel: +44 (0)1925 603508