Transcript IET_Portsmouth_110217

MRI: Seeing inside people!
Dr Simon J Doran
CRUK-EPSRC Cancer Imaging Centre, Institute of Cancer Research, Sutton, Surrey
Department of Physics, University of Surrey
Summary of today’s talk
• Brief history of medical imaging
• A few basic principles
• The human brain as seen by MRI
• What else can MRI do?
History of medical imaging
• There is a lot of evidence that the ancient Greeks performed major
surgery as early as 150 BC.
• But how did they know what was inside the body?
History of medical imaging
• Up until the very end of
the 1800’s, the only way to
find out about what was
inside the human body
was to find somebody who
was already dead and cut
them up.
“The Anatomy Lecture of Dr. Nicolaes Tulp” [1632] by Rembrandt
• This is not very useful if you want to find out what is wrong with
somebody who is alive and cure them!
History of medical imaging
Mrs Roentgen’s hand
Painting of woman having an x-ray (1896)
Modern x-ray Data: Mayo Clinic
• Things changed for ever in 1895 with the discovery of X-rays by
Wilhelm Roentgen.
History of medical imaging
• The problem with x-ray imaging
is that you can only see flat 2-D
images.
• By shining x-rays through the
body at a variety of different
angles all round the body, we
can reconstruct images that are
three-dimensional.
Sir Godfrey Hounsfield and his x-ray CT scanner
• In 1972, Sir Godfrey Hounsfield made the breakthrough that earned him
the Nobel Prize.
History of medical imaging
Data :Toshiba AmericaVisuals : Vital Images
X-ray CT visualisation: Vital Images
• X-ray CT is particularly good for seeing bones and blood vessels.
History of medical imaging
Sir Peter Mansfield and Paul Lauterbur, Photo: AFP
Data source : SMIS Ltd
• Just two years later (1974), these two men invented the MRI scanner
• They got the Nobel Prize, too, but they had to wait till 2003.
• MRI is really good at taking pictures of the brain.
Why use different methods of imaging?
• Plane-film X-ray maps the total
attenuation of X-rays along a path
through the body, giving a projection
image. Good for bone structure in
accidents.
Data: Mayo Clinic
• X-ray CT measures the X-ray attenuation
coefficient of the body at each point. True
3-D images.
• Ultrasound maps the reflection and
attenuation of sound.
Data: Clearview Ultrasound
Data :
Toshiba
Visuals : Vital Images
Why use different methods of imaging?
• MRI maps the distribution and
“environment” of water
molecules in the body.
• PET maps the distribution of
radioactively labelled
compounds.
Data source: SMIS Ltd
• MEG maps directly the magnetic
Data: CSUA, Berkeley
fields generated by currents
flowing in the brain.
Data: FORENAP, Rouffach
What is the tunnel into which the patient slides?
Image sources : GE Medical Systems, VA Imaging Centre, University of Florida
What happens in a scan?
• Resonant frequency is related to the magnetic field.
f  B
• If we vary the magnetic field across the sample, then the
frequency of emitted radio waves varies.
• By looking at the frequency spectrum of the signal, we
can find out how many spins are where.
B
Feet
Head
x
Why do MRI scanners make a noise?
• A gradient coil is just like a big loudspeaker (i.e., a large coil of
wire sitting in a magnetic field).
• As we change the current passing through the coil the whole
gradient assembly (many tons) tries to move.
• It is held in place very securely, yet still vibrates a little,
particularly at certain frequencies.
• An expert can tell what imaging scan is being done by listening
to the sound the gradients make.
Scout
T1-W gradient echo
EPI
The Human Brain as seen by MRI
Data: The Whole-brain Atlas, K. A.
Johnson and J. A. Becker, Harvard
Data: Christopher Nimsky, Neurosurgery,
Erlangen, Germany
Where are we heading with anatomical MRI?
7T
Data source: SMIS
Data source: Gachon University, Seoul
Where are we heading
with anatomical MRI?
4.7 T
Stained section
1.5 T
Data source: Roger Ordidge, UCL
MRI in research: Functional imaging
• We acquire one image of the
brain in a “resting” state.
• We follow this by a
corresponding image where
the brain is active.
• Any differences between
these two images correspond
to places where the brain is
working.
Data source:
http://www.youtube.com/watch?v=alS3GeRxYGY
• We can see you think!!
MRI in research: Functional imaging
• Typical base data (greyscale) at 4.7 T, leading to the activation
time course (right) and subsequent overlaying of activated
areas on images (yellow-red scale)
Data source: Roger Ordidge, UCL
MRI in research: neural fibre tracking
• MR images can be sensitised
to the rate of diffusion of
water molecules.
• Water diffuses faster along
nerve fibres than
perpendicular to them.
• This allows us to map the
Nerve fibre
local direction of a fibre and
create a map of the fibres.
Data source: Geoff Parker, University of Manchester
MRI in research: neural fibre tracking
• MR images can be sensitised
to the rate of diffusion of
water molecules.
• Water diffuses faster along
nerve fibres than
perpendicular to them.
• This allows us to map the
local direction of a fibre and
create a map of the fibres.
• Finally, we can overlay them
on a high-resolution 3-D
image of the head.
Data source: Wilde et al. 2008
MRI in research: neural fibre tracking
Data source: Wakana et al., Radiology 2004; 230:77–87
MRI in research: neural fibre tracking
Data source: András Jakab. (University of Debrecen)
MRI-guided neurosurgery
• State-of-the-art neurosurgery unit at Erlangen, Germany.
• MRI is completely integrated into the operating theatre
and used in conjunction with digital images captured
from an operating microscope.
Data source : Christopher Nimsky, Neurosurgery, Erlangen, Germany
MRI-guided brain surgery
• The surgeon can see both the patient and MR image on
the same display.
Data source : Christopher Nimsky, Neurosurgery, Erlangen, Germany
So, what else can we do with MRI?
MRI-guided thermotherapy
• Basic premise: Heating
tumour tissue in vivo can
destroy tumours by “cooking
them”
• The basic requirements of
the system are:.
 a heating device
 a method of monitoring the
heating in 3-D
 a method of controlling the
heating based on feedback
from the monitoring
Data source : Chrit Moonen, University of Bordeaux, France
MRI-guided thermotherapy
• The MR signal can be made sensitive to temperature,
allowing a temperature map to be made over a 3-D region
in a matter of seconds.
• The heating source is a focused ultrasound transducer,
built into the scanner’s patient table.
f
Data source : Chrit Moonen, University of Bordeaux, France
z
x
MRI-guided thermotherapy
Colours indicate temperature distribution
Muscle
Water
Transducer
MR image with temperature
map overlaid
Planned temperature change,
with measured values
Data source : Chrit Moonen, University of Bordeaux, France
MRI-guided surgery: catheter placement
Ø = 2 mm
Schematic of homebuilt catheter
Realisation of catheter
Data source : Stefan Petersson, Malmö, Sweden
MRI-guided surgery: catheter placement
TrueFISP pulse sequence (linear)
TR/TE/FA
5.1 ms / 2.6 ms / 70o
Pixelsize
2.0 x 2.0 x 200.0 mm3
Matrix 64x 128
Scan time
300 ms / projection
Off-line reconstruction
13C
MR guided renal intervention
Data source : Stefan Petersson, Malmö, Sweden
MRI in research: Stem cell imaging
cell
Iron-oxide
nanoparticles
Unlabelled stem cells
factor 50 higher iron content
Data source: Peter Jakob, University of Wurzburg, Germany
Magnetically labelled cells
MRI can image much more than just the brain ...
Data source : Siemens Medical
MRI can image much more than just the brain ...
Data: www.journey-with-crohns-disease.com
Data: David Lomas, Addenbrokes Hospital
A virtual tour of the human colon ...
Sports injuries ...
Data: www.imaios.com/en/e-Anatomy/Limbs/Knee-MR
Data: Paul Debevec
… and the diagnosis, Mr Beckham ...
Data source: American Radiology Services
Conclusion
• There are many different ways of imaging the
human body.
• The different methods tell us different things.
• It is study of basic Physics (electromagnetism,
nuclear physics, mechanics) which has
discovered the principles.
• It is money — the human brain is a very valuable
thing — which has led to the incredible
developments that we see today.
The End
Thank you for listening!
Any questions?