MRS working ,principle

1. Magnetic Resonance
Spectroscopy (MRS)
Complete Presentation with
Diagrams, Icons & Visuals

2. Introduction
• • Advanced MRI technique
• • Provides biochemical/metabolic information
• • Complements routine MRI
• • Detects tissue metabolites

3. Principle of MRS
• • Based on chemical shift phenomenon
• • Different molecules resonate at different
frequencies
• • Frequencies measured in ppm
• • Produces metabolic spectrum (graph)

4. Chemical Shift
• • Small frequency variations due to molecular
environment
• • Each metabolite has distinct ppm position
• • Enables identification of molecules

5. Common Metabolites & Their
Peaks
• • NAA (2.0 ppm) – neuronal marker
• • Choline (3.2 ppm) – cell turnover
• • Creatine (3.0 ppm) – energy reference
• • Lactate (1.3 ppm) – anaerobic metabolism
• • Myo-inositol (3.5 ppm) – glial marker
• • Lipids (0.9–1.3 ppm) – necrosis marker

6. Techniques of MRS
• • Single Voxel Spectroscopy (SVS) –
PRESS/STEAM
• • Multi-Voxel Spectroscopy (CSI) – metabolic
maps
• • Used for large lesions

7. Acquisition Parameters
• • TE: Short (20–35 ms) & Long (135–144 ms)
• • TR: 1500–2000 ms
• • Voxel size: 1–8 cm³
• • Shimming improves B0 uniformity

8. Spectrum Interpretation
• • Peaks show metabolite concentration
• • Ratios used for diagnosis:
• - ↑ Cho/Cr → tumor
• - ↓ NAA/Cr → neuronal loss
• • Lactate doublet inversion at long TE

9. Applications – Tumors
• • ↑ Choline
• • ↓ NAA
• • Lipids/lactate indicate high-grade tumor
• • Differentiates tumor recurrence vs radiation
necrosis

10. Applications – Stroke
• • ↓ NAA early
• • ↑ Lactate due to anaerobic metabolism
• • Useful in acute ischemia

11. Applications – Epilepsy
• • ↓ NAA in seizure focus
• • Helps in pre-surgical mapping

12. Applications – Demyelination
• • ↑ Choline
• • ↓ NAA
• • ↑ Myo-inositol (gliosis)
• • Important in MS evaluation

13. Applications – Infection / Abscess
• • Absence of normal metabolites
• • Presence of lactate, amino acids, acetate,
succinate
• • Differentiates abscess vs necrotic tumor

14. Applications – Metabolic Disorders
• • ↑ Lactate in mitochondrial disorders
• • ↑ Glutamine in hepatic encephalopathy
• • Useful in leukodystrophies

15. Advantages
• • Non-invasive biochemical analysis
• • Early detection before structural changes
• • Helps tumor grading
• • Differentiates necrosis vs abscess

16. Limitations
• • Motion sensitivity
• • Low SNR in small voxels
• • Long acquisition times
• • Requires expert interpretation

17. Summary
• • MRS = metabolic imaging using chemical
shifts
• • Detects metabolites like NAA, Cho, Cr,
lactate
• • Useful in tumors, epilepsy, stroke, MS &
metabolic diseases

18. Key Metabolites
NAA Cho Cr
Lactat
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mI

19. MRS Spectrum (Diagram)
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