MR Spectroscopy of the Brain

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MR Spectroscopy of the Brain

• Todd Richards, PhD
• Department of Radiology
• University of Washington

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List of MRS Collaborators

• Stephen Dager Martin Kushmerick
• Neva Corrigan Kevin Conley
• Ken Maravilla Stefan Posse
• Ken Marro Jeff Stevenson
• Dennis Shaw Jenee OBrien
• Elizabeth Aylward Seth Friedman
• Natalia Kleinhans Helen Petropoulos
• Kurt Weaver Olivia Liang
• Eric Shankland Sandra Juul
• Ione Fine Ken Krohn
• Clark Johnson KC Stegbauer
• Cecil Hayes Mark Mathis

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Magnetic Resonance Spectroscopy

• MR spectroscopy is a technique for non-invasively
  measuring certain chemicals in the body.
• This technique can be performed on most MR
  scanners with MRS acquisition software enabled.
• MRS can measure certain low molecular weight
  chemicals

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Why is MRS important in the brain?

• The brain has a delicate balance of
  neurotransmitters and metabolites that if
  disrupted can lead to or be associated with
  neurological illness.
• For example in multiple sclerosis, MRS has been
  shown to correlate with clinical symptoms far
  better than standard MRI
• Normal appearing white matter on MRI can have
  chemical abnormalities detected by MRS.

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History of MRS Evolution

• 1983 Yale (Shulmans group) and UC Berkeley
  (Budinger/Richards) were among the first to
  present proton MR spectroscopy of brain (ISMRM).
• 1984 Bottomleys invention of PRESS
• 1989 Frahms discovery of STEAM
• 1990s Development of multi-voxel techniques
  such as Chemical-shift imaging (CSI) and
  echo-planar spectroscopic imaging (PEPSI)
• 2000s Explosion of new papers on clinical use
  of MR spectroscopy in neurological and
  psychiatric disorders

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Here is a good book on MR Spectroscopy

• In Vivo NMR Spectroscopy Principles and
  Techniques, 2nd Edition Robin A. de Graaf
  ISBN 978-0-470-02670-0, 2007 edition

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Lactate Imaging using MR spectroscopy Lactate
has chemical shift and j-coupling properties
that can be used to separate it from other
chemicals in the body.
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CH3CHOHCOOH
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The 3 protons on the CH3 exchange energy and
split the proton on the adjacent carbon in the
lactate molecule which is detectable with MR
spectroscopy
CH3 part of lactate
CH part of lactate
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2-Dimensional J-resolved plot of phantom with
brain-like chemicals- Acquired on UW 3T
Philips X axis is standard chemical shift in
ppm Y axis is J-coupling dimension
Lactate NAA
GLU/GLN Cr Cho
GLU/GLN
2.0 3.0
PPM
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2-Dimensional J-resolved plot of phantom with
brain-like chemicals- Acquired on UW 3T
Philips X axis is standard chemical shift in
ppm Y axis is J-coupling dimension
Zoomed into the region 2.0 2.5ppm to show
Glutamate/Glutamine j-coupling
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2-Dimensional J-resolved plot of phantom with
brain-like chemicals- Acquired on UW 3T
Philips X axis is standard chemical shift in
ppm Y axis is J-coupling dimension
Zoomed into the spectral region 1.0 to 1.5 ppm
to show lactate j-coupling offsets
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Phosphorus MR Spectroscopy

• P-31 MRS can be used to measure tumor
• Phosphoenergetics such as ATP, Phosphocreatine
• P31 MRS can be used to measure tumor pH

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• Dr. Richards research projects that involve MRS
• Structural and Chemical Brain Imaging of Autism
• 2) The neural and functional effects of long term
  
• visual deprivation
• 3) Neuroprotection Following Perinatal Asphyxia
• 4) Molecular Imaging of Cancer and Its Response
• to Therapy
• 5) Effect of diet composition on liver fat and
• glucose metabolism

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MR spectroscopy techniques

• Proton MR spectroscopy (NAA, Cr, Choline)
• Single-voxel, Multi-voxel
• Spectral Editing in MR spectroscopy
• GABA, Glutamate, Lactate
• Phosphorus MR spectroscopy, ATP, PCr, Pi

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MEGAPRESS

• Technique to isolate chemicals based on their
  J-coupling characteristics
• For example, separation of GABA from creatine

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Creatine before subtraction
Choline before subtraction
GABA After subtraction
2.8 3.0 3.2 ppm
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Methods 1) Magnetic Resonance Imaging and
Proton Echoplanar- Spectroscopic Imaging MRI was
used to find the co-ordinates of the Sylvian
fissure and language regions of the brain and
provide anatomic registration for the PEPSI
slice. PEPSI is a technique for mapping
chemicals in the brain and is a multi-voxel MR
spectroscopy technique. GE version of PEPSI
(5.8) - K. Marro and T. Richards PEPSI was
acquired using the following parameters TR/TE
4000/272 milliseconds 20 mm thick
slice 256x32x32 acquisition matrix with 32x32
spatial matrix that spans a 22 cm field of
view 256 chemical-shift points for spectral
information Acquisition time of 4.5
minutes Voxel size of 20x6.8x6.8 mm
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PEPSI Pulse Sequence for controlling the MR
scanner parameters Radiofrequency- RF, magnetic
field gradients- Gx, Gy, Gz
15 X
2 X
8 X
RF
G
x
G
y
G
z
OVS 1
WS 3
OVS
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WS 12
Slice Selection
Spatial-Spectral Encoding
TE
WS water suppression, OVS outervolume
suppression Original code developed by Stefan
Posse
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Methods 2) Language Tasks Used For Brain
Activation A full package of language and
non-language stimuli were developed and
computerized for software psyscope (Corina et
al) I) Phonological task - 2 word rhyming
task II) Lexical Access task - 2 word semantic
task III)Tone task - non-language tone
differentiation task IV) Passive listening -
listening to words without performing a judgement
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Conclusions

• MR Spectroscopy of the brain can be used to
  measure metabolic changes in health and disease.
• New advances in MRS localization allow for
  regional/image analysis of the brain
• New advances in chemical selectivity allow for
  separation of previous undetectable chemicals
  such as GABA