1H Magnetic Resonance Spectroscopy MRS

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1H Magnetic Resonance Spectroscopy (MRS)

• Introduction
• commonly detectable metabolites
• commonly used 1H MRS data acquisition methods
• examples of 1H MRS applications in studies of
  neurodisorders and breast cancer

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Introduction

• useful and important as an additional evaluation
  tool for various neurodisorders, such as brain
  cancer, stroke, epilepsy, Alzheimers disease,
  multiple sclerosis, etc.
• Neuro 1H MRS scans reimbursable.
• Research beyond neuro-applications
• breast cancer
• prostate cancer, etc.

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Commonly detectable Brain Metabolites at low
field strength (? 1.5T)

• N-acetylaspartate (NAA)
• neuronal marker
• 2.02 ppm
• Total creatine (Cr creatine and phosphocreatine)
• Energy storage molecules in tissue
• Stable concentration, as internal reference in
  MRS studies
• 3.03 ppm
• Choline compounds (Cho phosphocholine, glycero-
  phosphocholine)
• cell membrane turnover
• precursor of molecules for cellular signal
  transduction
• 3.23 ppm
• Lactate (Lac)
• anaerobic glycolysis
• 1.33 ppm

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• Myo-inositol (mI)
• glial marker
• precursor of molecules for cellular signal
  transduction
• 3.56 ppm
• Higher filed strength (? 3 T)
• improved S/N, spectral resolution
• more detectable metabolites, such as Gaba
• separating glutamate and glutamine
• 13C MRS --- glucose metabolism
• 31P MRS --- energy metabolism

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Common 1H MRS data acquisition

• PRESS (Point RESolved Spectroscopy,
  90o-180o-180o)
• stronger signal, long TE application
• STEAM (STimulated Echo Acquisition Mode,
  90o-90o-90o)
• weaker signal, short TE application
• Water suppression (H2O 50 M, metabolites 1-10
  mM)
• CHESS (chemical shift selective) pulses for
  saturation
• Single voxel
• Multi-voxel (CSI, MRSI)
• 2D, multi-slice
• 3D

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• PRESS sequence

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• STEAM sequence

90o
90o
TE/2
TM
TE/2
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Single-Voxel MRS Studies of Alzheimers
Disease(Neurology 2001 57 626-632)
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1H MRSI Study in Multiple Sclerosis
(TE/TR 135/1500 ms)
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Common 1H MRS data quantitation

• Metabolite ratio (ratio of peak areas) NAA/Cr,
  Cho/Cr
• Absolute quantitation mmol/tissue volume
• Internal reference Cr, H2O
• Phantom replacement method --- correction for
  coil load
• External reference --- correction for B1
  inhomogeneity
• MRS signals are both T1 and T2-weighted,
  corrections for differences in T1 and T2 between
  in vivo tissue and aqueous solution environments.

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Single-Voxel MRS Studies of Alzheimers
Disease(Neurology 2001 57 626-632)
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Single-Voxel MRS Studies of Alzheimers Disease
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Single-Voxel MRS Studies of Alzheimers Disease
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Single-Voxel MRS Studies of Down Syndrome ( Am J
Psychiatry 1999 156 1879-1886)
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Single-Voxel MRS Studies of Ts65Dn Mouse---Down
Syndrome Model (NeuroReport 2000 11 445-448)
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Single-Voxel MRS Studies of Ts65Dn Mouse---Down
Syndrome Model
Li

• mI mI-1- phosphate

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1H MRSI Study in Multiple Sclerosis
(TE/TR 135/1500 ms)
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• Significant correlations between NAA/Cho, NAA/Cr,
  CCSF volume fraction (of the total brain and CSF
  volume), and BRB scores

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Relation between overall neuropsychological
performance and standardized predicted score from
a multiple regression model including central
cerebral atrophy, lesion volume, and RPPV NAA/Cho
(R - 0.785 p lt .001)
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NAA quantification using CSF water as internal
reference

• Reference MRSI scan without water suppression, 1
  scan average, other parameters kept the same
• Water signal from CSF voxel as internal reference
• NAA/H2O ratio corrected for CSF volume fraction
  in the MRS voxel.

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1H MRS Study of Breast Cancer

• High false positive rate (60-80) in conventional
  mammography, resulting unnecessary biopsy.
• Recently, dynamic contrast enhancement (DCE)
  T1-weighted MRI ---- an integral part of a
  standard breast cancer diagnostic protocol.
• Excellent sensitivity (88-100)
• Specificity rather variable (37-97)

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1H MRS Study of Breast Cancer

• Promising tools for improving specificity in
  detection of breast malignancy
• 1H MRS
• Perfusion T2-weighted MRI
• 1H MRS measurement
• detection of enhancing Cho signal, marker of
  active tumor

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1H MRS Study of Breast Cancer
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1H MRS Study of Breast Cancer
Single-voxel MRS, PRESS (TE/TR 135/2000 ms)
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1H MRS Study of Breast Cancer

• DCE MRI
• 100 sensitivity, no false negative
• 9 out of 39 positive turned out benign by biopsy
• ------ 77 specificity.
• DCE MRI MRS
• no false negative
• 3 out of 26 MRS cases turned out false positive
  ------ 88 specificity

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1H MRS Study of Brain Cancer

• In recent years, in addition to conventional pre-
  and post-contrast MRI, several other MR
  techniques have been used for the diagnosis and
  evaluation of brain tumors.
• 1H MRS diagnosis, clinical evaluation of tumor
  response to therapy, differentiate tumor
  recurrence and radiation necrosis.
• Elevated Cho signal is a marker of viable tumor
• Diffusion Weighted Imaging (DWI)
• differentiate necrosis, edema, and viable
  tumor regions.
• Perfusion Imaging
• evaluate tumor vascularity, assess tumor grade.

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Monitoring tumor response to intracarotid therapy
using MRS
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Post-contrast T1 Images and Proton Spectra of a
Patient with CNS Lymphoma

• Pre - ICC Post - 1st ICC
  Post - 4th ICC

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ADC and rCBV Maps of a Patient with CNS Lymphoma

• Pre - ICC Post - 1st ICC
  Post - 4th ICC

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Localization of Spectroscopic Voxel for a Patient
with Metastatic Squamous Cell Carcinoma
1H MRS for Monitoring Head and Neck Cancer
Response to Therapy

• Pre-therapy Post-therapy

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Proton Spectra of a Patient with Metastatic
Squamous Cell Carcinoma

• Pre-therapy Post-therapy

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Localization of Spectroscopic Voxel for a Patient
with Squamous Cell Carcinoma

• Pre-therapy Post-therapy

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Proton Spectra of a Patient with Squamous Cell
Carcinoma

• Pre-therapy Post-therapy

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Changes of Cho/Water Ratio for Head and Neck
Tumor Patients
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Discriminating Neoplastic and Non-neoplastic
Thyroid Lesions Using 1H MRS

• 29 patients with thyroid lesion
• 1H MRS examination
• PRESS single-voxel (TE/TR 135/2000)
• at lesion (n 29) and at normal contralateral
  side (n5)
• from healthy control (n2)
• Resection of thyroid mass within one week

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Proton spectra from neoplastic thyroid lesion and
normal-appearing contralateral region
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• Non-neoplastic thyroid lesion Normal healthy
  control

Lip/Lac
Cho
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Significant difference in Cho/Water ratio between
neoplastic (3.36 ? 2.55, n22) and non-neoplastic
(0.16 ? 0.11, n7) thyroid lesions
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Results

• Thyroid neoplasm
• Cho/water gt 1.0 x 10-3
• Thyroid non-neoplasm
• Cho/water lt 0.4 x 10-3

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Conclusion

• Strong correlation between MRS and pathology
  results
• Its difficult to distinguish neoplastic from
  non-neoplastic thyroid lesions based on
  conventional post-contrast T1-weighted images, as
  both are usually enhanced.
• 1H MRS can be a valuable screening tool with high
  sensitivity in detection of thyroid neoplasm.
• Aid in treatment planning and evaluation of
  post-operation recurrence and node/metastasis.

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Proton MRS Studies of Pediatric Neurodisorder
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1H MRS Study of a child with NKH(Non Ketotic
Hyperglycinemia)(J Neuroimaging 2001 11
209-212)
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WM proton spectra at 10 and 13 months(TE/TR
270/2000)
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Correlation of plasma and brain glycine levels
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1H MRS Study of a child with ADEM(Acute
Disseminated Encephalomyelitis)
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• Brain Metabolite Ratios in a Child with ADEM
• MRS Study NAA/Cr Cho/Cr Lac/Cr
• Voxel
• BG initial 0.71 0.76 0.51
• BG follow-up 0.83 0.88 0.21
• WM initial 1.62 0.91 0.00
• WM follow-up 1.38 1.10 0.00

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In vivo 1H MRS study of a rat model of
autism(Physiol Behav 2002 75 403-410)
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PRESS (TE/TR 40/2000), 0.2 cc voxel size
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Significant decrease of NAA/Cr in autistic rats
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Significant increase of Cho/Cr in autistic rats
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Significant increase of mI/Cr in autistic rats
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1H MRS study of autistic human subjects(PRESS,
TE/TR 40/2000)
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1H MRS study of autistic human subjects(PRESS,
TE/TR 40/2000)
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1H MRS study of autistic human subjects(PRESS,
TE/TR 40/2000)
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1H Spectra from Healthy Controls

• Left Hipp-Amyg Cerebellum

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1H MRS study of autistic human subjects

• Metabolite Ratios in Children with PDD (N 10)
  and Healthy Controls (N 6)
• LHA RHA Cerebellum
• PDD Control PDD Control PDD Control
• NAA/Cr 1.97 ? 0.32 2.42 ? 0.32 1.94 ? 0.51
  2.88 ? 0.65 1.45 ? 0.23 1.38 ? 0.12
• Cho/Cr 0.72 ? 0.21 0.47 ? 0.17 0.68 ? 0.22
  0.54 ? 0.28 0.75 ? 0.24 0.46 ? 0.11
• mI/Cr 0.78 ? 0.26 0.50 ? 0.17 0.72 ? 0.31
  0.39 ? 0.13 0.51 ? 0.17 0.20 ? 0.12
• mean ? SD mean in PDD group differs
  significantly from the control group (unpaired
  t-test, p lt 0.05).