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Nuclear Magnetic Resonance (NMR) Flashcards

1
Q

What does NMR stand for?

What happens?

A

Nuclear Magnetic Resonance

Nucleus and Electrons remain unchanged in NMR

–> no radioactive (ionizing) radiation

–> no chemical reaction

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2
Q

What are different MR imaging and Spectroscopy techniques?

A

Single Vocel NMR ~16kb (one image)

2D Spectroscopic Imaging ~16MB (32x32 images)

3D SI ~512MB (32x32x32 images)

3D MRSI + multiarray coils ~4GB (8 coilsx512MB)

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3
Q

What properties does the nucleus have?

A

Spin (angular moment)

Magnetic moment

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4
Q

What are the basic principles of NRM?

A

Magnetic field gradients to obtain spatial information

Nuclear spin

Magnetic dipole moment

Chemical Shift:

  1. Different electronic surroundings
  2. Different magnetic shielding electronic clouds induce a magnetic moment opposed to the static field
  3. At the nucleus the magnetic field is slightly different from B0
  4. Resonance frequency
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5
Q

How is a voxel selected?

A

Selcetion of three Orientations:

  • Phase- Direction
  • READ - Direction
  • SLICE selection
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6
Q

What can in vivo metabolic imaging be used for?

A

Thousands of studies:

Epilepsy, Multiple Sclerosis, Alzheimer, Dementia, Oncology, Parkinson, AIDS, etc.

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7
Q

What types of Image Contrasts are there?

A

Proton-Density

T2-Weighting: Transverse Relaxation T2

T1-Weighting: Longitudial Relaxation T1

Diffustion

Flow

BOLD

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8
Q

What is fMRI?

+ Examples

A

functional-MRI

Blood Oxygenation Level Dependent MRI (BOLD):
To measure brain activation

Motor Stimulation

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9
Q

What is MR Angiography?

A

Visualize Blood vessels

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10
Q

What is the dixon techique?

A

Compare Fat & water images

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11
Q

What are the potential risks of MRI?

A

Metal, pacemaker, heating

But no radiation

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12
Q

What is the basic principle of 1D 1H-NMR?

A
  • All protons in a molecule yield a peak
  • Position depends on electronic surroundings of the proton
  • Intensity / Area depends on:
    • number of contributing protons
    • concentration

–> Can be used to distinguish different functional groups in a molecule

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13
Q

What is T2?

A

Transverse Relaxation

Signal intensity decreases exponentially over time

Show contrast over Echotime TE

Different images between long and short TE

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14
Q

What is T1?

A

Longitudinal Relaxation

Signal incerases exponentially over time

Show contrast over repetitiontime TR

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15
Q

What is done in a targeted analysis?

A

Deconvolution:

  • Metabolic profiling
  • Identification / quantification

Fitting:
Position, Intensity, Linewidth, (Phase)

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16
Q

What is done in a non-targeted analysis?

A

Statistics:

  • Metabolic fingerprinting
  • Classification / discrimination

PCA/PLS-DA (like PCA with additional information)

17
Q

What are possible pitfalls of metabolomics in practice?

18
Q

What is the general workflow in metabolomics by NMR in practice?

A
  1. Sample Collection:
    • Dietary control
    • Time of sampling
    • Storage container
    • Storage conditions
    • …
  2. Sample Preparation:
    • Urine:
      • Buffering
      • pH adjustment
      • NaN3
      • Reference
    • Blood:
      • Heparin tube
      • Saline
      • Cenrifuge
      • Reference
    • Tissue/Cells:
      • Intact tissue or extract (Perchloric acid or methanol/chloroform
  3. NMR measurement:
    • 1H-NMR (HR-MAS):
      • 1D:
        • Dominating
        • <10 min
        • Automated
      • CPMG/Project:
        • Separation of small components from:
          • Protein
          • Lipids
      • 2D J-resolced:
        • reducing spectral congestion (separating chemical shift from coupling)
      • HSQC:
        • Expensive
        • Time consuming
        • Mostly for identification
    • More rare: 13C-NMR:
      • HSQC (see above)
  4. Analysis:
    • Multivariate Analysis:
      • Spectral pre-processing
      • Bucketing
      • Scaling
      • PCA/PLS
      • Machine/Deep Learning
  5. Identification:
    • Databases
    • Advanced NMR methods (COSY, TOCSY, HSQC)
  6. Biochemical interpretation:
    • Mechanistic insights
19
Q

What does NMR allow for?

What are possible applications?

A

NMR allows the measurement, identification and quantification of hundreds of metabolites simultaneously from liquids or biopsies

Applications:

  • Metabolomic Applications:
    • Toxicity Screening & Disease Diagnosis
  • HR-MAS NMR:
    • biomedical studies like Cancer Metabolomics
    • food science
  • Metabolomics NRM-study of Body Fluids
20
Q

What is clinical NMR?

A
  • Extremely versatile and important in clinical routine as MRI
  • Clinical in vivo NMR important in selected cases, but not yet established as routine investigation
  • Clinical ex vivo NMR important in selected cases using (targeted) individual peak analysis
  • NMR Metabolomics:
    • Potential shown in oncology
    • Still quite few studies, especially of tissues/biopsies

Proteomics & Metabolomics (4 decks)

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