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1H Magnetic Resonance Spectroscopy MRS

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Title: 1H Magnetic Resonance Spectroscopy MRS


1
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

2
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.

3
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

4
  • 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

5
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

6
  • PRESS sequence

7
  • STEAM sequence

90o
90o
TE/2
TM
TE/2
8
Single-Voxel MRS Studies of Alzheimers
Disease(Neurology 2001 57 626-632)
9
1H MRSI Study in Multiple Sclerosis
(TE/TR 135/1500 ms)
10
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.

11
Single-Voxel MRS Studies of Alzheimers
Disease(Neurology 2001 57 626-632)
12
Single-Voxel MRS Studies of Alzheimers Disease
13
Single-Voxel MRS Studies of Alzheimers Disease
14
Single-Voxel MRS Studies of Down Syndrome ( Am J
Psychiatry 1999 156 1879-1886)
15
Single-Voxel MRS Studies of Ts65Dn Mouse---Down
Syndrome Model (NeuroReport 2000 11 445-448)
16
Single-Voxel MRS Studies of Ts65Dn Mouse---Down
Syndrome Model
Li
  • mI mI-1- phosphate

17
1H MRSI Study in Multiple Sclerosis
(TE/TR 135/1500 ms)
18
  • Significant correlations between NAA/Cho, NAA/Cr,
    CCSF volume fraction (of the total brain and CSF
    volume), and BRB scores

19
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)
20
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.

21
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)

22
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

23
1H MRS Study of Breast Cancer
24
1H MRS Study of Breast Cancer
Single-voxel MRS, PRESS (TE/TR 135/2000 ms)
25
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

26
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.

27
Monitoring tumor response to intracarotid therapy
using MRS
28
Post-contrast T1 Images and Proton Spectra of a
Patient with CNS Lymphoma
  • Pre - ICC Post - 1st ICC
    Post - 4th ICC

29
ADC and rCBV Maps of a Patient with CNS Lymphoma
  • Pre - ICC Post - 1st ICC
    Post - 4th ICC

30
(No Transcript)
31
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

32
Proton Spectra of a Patient with Metastatic
Squamous Cell Carcinoma
  • Pre-therapy Post-therapy

33
Localization of Spectroscopic Voxel for a Patient
with Squamous Cell Carcinoma
  • Pre-therapy Post-therapy

34
Proton Spectra of a Patient with Squamous Cell
Carcinoma
  • Pre-therapy Post-therapy

35
Changes of Cho/Water Ratio for Head and Neck
Tumor Patients
36
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

37
Proton spectra from neoplastic thyroid lesion and
normal-appearing contralateral region
38
  • Non-neoplastic thyroid lesion Normal healthy
    control

Lip/Lac
Cho
39
Significant difference in Cho/Water ratio between
neoplastic (3.36 ? 2.55, n22) and non-neoplastic
(0.16 ? 0.11, n7) thyroid lesions
40
Results
  • Thyroid neoplasm
  • Cho/water gt 1.0 x 10-3
  • Thyroid non-neoplasm
  • Cho/water lt 0.4 x 10-3

41
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.

42
Proton MRS Studies of Pediatric Neurodisorder
43
1H MRS Study of a child with NKH(Non Ketotic
Hyperglycinemia)(J Neuroimaging 2001 11
209-212)
44
WM proton spectra at 10 and 13 months(TE/TR
270/2000)
45
Correlation of plasma and brain glycine levels
46
1H MRS Study of a child with ADEM(Acute
Disseminated Encephalomyelitis)
47
  • 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

48
In vivo 1H MRS study of a rat model of
autism(Physiol Behav 2002 75 403-410)
49
PRESS (TE/TR 40/2000), 0.2 cc voxel size
50
Significant decrease of NAA/Cr in autistic rats
51
Significant increase of Cho/Cr in autistic rats
52
Significant increase of mI/Cr in autistic rats
53
1H MRS study of autistic human subjects(PRESS,
TE/TR 40/2000)
54
1H MRS study of autistic human subjects(PRESS,
TE/TR 40/2000)
55
1H MRS study of autistic human subjects(PRESS,
TE/TR 40/2000)
56
1H Spectra from Healthy Controls
  • Left Hipp-Amyg Cerebellum

57
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).
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