This presentation discusses the basics of Magnetic Resonance Spectroscopy. provides the first step for researchers and medical students who are interested in gaining knowledge in this field.
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MRS REVEALS METABOLIC CHANGES
1. BY HAIDY ELBIADY.
IMG, WASHINGTON UNIVERSITY OF HEALTH
AND SCIENCE.
MAGNETIC RESONANCE
SPECTROSCOPY(MRS)
2. DEFINITION
• MRS is a noninvasive test that studies
metabolic change in brain tissue that could be
related to different pathological
processes without using ionizing radiation,
utilizing a special program in the MRI machine.
• known as in vivo Magnetic Resonance
Spectroscopy or Nclear Magnetic Resonance
(NMR) spectroscopy.
3. • MRS can't be interpreted without
conventional MRI, to increase the specificity
and ability of predicting the histological grades.
• Difference between the 2 modalities are
discussed in the following slides.
5. MRI VERSUS MRS
• MRI is ued to identify the location
of the possible brain tumor.
• MRS is used to Compare normal
brain tissues with the abnormal tumor tissues.
• And to detect tissue changes in CVS and Epilepsy.
MRI MRS
6. MRI VERSUS MRS
MRI
• Includes strong magnet
• Uses radio waves
• Computer used to create detailed images.
MRS
• A series of tests which are added to MRI scan of
the brain or spinal cord to measure the chemical
metabolism of suspected tumor or a disease
process.
7. MRS USES
• MRS charts biochemical change which can lead to early detection of brain disease such as tumors,
because biochemical change proceeds anatomical changes detected by conventional imaging studies.
Keep in mind that results varies according to the patient age, region of the brain affected and technique
used.
• To detects metabolic changes of brain tissues due to diseases which may not be seen in
the conventional structural images.
• To differentiate among diseases:
1) grade and classify tumors detected by MRI .
2) differentiate neoplasm from different similar lesion on MRI.
• To monitor response to therapeutic treatment.
• May help in understanding the pathophysiology of different diseases, for research purposes.
8. • MRS measures about 7 different types of metabolites, their frequencies are
measured in parts per million (PPM).
• Detecting the disease by comparing the frequencies of theses metabolites with
normal brain metabolites' frequencies.
• For better results, water and fat suppression techniques should be used, to be
able to detect the frequencies of theses metabolites.
Y axis indicate
metabolite concentration.
X axis indicate the chemical
shift of the metabolite.
Measured by part per
million PPM.
10. METABOLITES DETECTED BY MRS
• Found in neurons of adult brain
• low in newborns (increases over 2 years till reach the adult values.)
• Indicator of neuronal density and viability.
• Plays a role in the formation of myeline sheath.
• Regulates osmosis
1) N- Acetyl Aspartate (NAA):
11. METABOLITES
DETECTED BY MRS
1) N- Acetyl Aspartate (NAA):
• Resonate at 2 ppm.
• Increased levels only in Canavan's disease,
which is caused by missing
enzymes responsible for degradation
of NAA, leading to its accumulation.
• Decreases levels in neurodegenerative
diseases; hypoxia, demyelination and brain
tumor.
12. METABOLITES
DETECTED BY MRS
2) Creatine:
• Resonates at 3 ppm
• Used as a marker of energy
production and intracellular
metabolism.
• Decreased levels may be shown in
high grade astrocytoma.
13. METABOLITES
DETECTED BY MRS
3) Choline
• Resonates at 3.2 ppm.
• Normally increases in the growing
brains of infants as the myelin sheath
develops.
• Marker of cell membrane proliferation.
• Levels increase in brain tumors,
multiple sclerosis and leukodystrophy.
Normal
High Cholin in MS
14. METABOLITES
DETECTED BY MRS
4) Lactate :
• Lactate level increase indicates
anaerobic metabolism. It
is almost not present under
normal conditions.
• High levels suggest either
ischemic brain disease/hypoxia or
inflammatory process( acute
inflammation)
• Mitochondrial diseases. And
seizures also known to increase
lactate levels.
15. METABOLITES
DETECTED BY MRS
5) Lipid:
• Results from breakdown of
tissues like necrosis of a brain
mass or radiation necrosis(
necrosis of normal tissues due to
radiation therapy for malignant
tumors .)
• Multiple sclerosis increases
lipid due to
increased myelin breakdown.
• False positive results can be
due to scalp fat.
16. METABOLITES DETECTED
BY MRS
6) Myoinositol:
• Peaks at 3.5-3.56.
• Synthesized in the glial cells, so it
is considered a marker for
glial cells.
• High levels is detected in gliomas,
Alzheimer disease, inflammation
and gliosis.
19. APPLICATIONS:
1)Study of intracranial space occupying
lesion:
• By analysing spectra and metabolites
ratio in the uncertain zones ( area
separating the mass and apparently
normal brain tissues) .You can get
more information about the possible
progression of the cancer cells,
predicting the best area for
stereotactic biopsy which helps guide
further treatment in patients with
high risk of recurrence.
20. 2) EVALUATING TUMOR STAGING:
High grade glioma
choline peak and low NAA indicate
high cell proliferation and low
neuronal integrity .
Low grade glioma
Normal NAA and high choline
21. 3) ASSESSING
PRIMARY VERSUS
METASTATIC
BRAIN TUMORS
Primary brain malignancy Metastatic
• High NAA peak.
• High choline peak.
• Possible high lipid and lactate
in high grade tumors.
• Peripheral infiltration
(abnormal peripheral spectra)
• Intratumorally choline peak
• No choline elevation in the
Peritumoral edema.
• Low NAA.
• No peripheral infiltration
( normal peripheral spectra)
22. 4) Follow up and assessing treatment response:
• Persistent elevation of choline peak after tumor resection +/-
radiotherapy may indicates either tumor recurrence or treatment
unresponsiveness.
• Tumer recurrence shows high choline spectrum, low NAA and high
lactate, while radiation necrosis will show low choline and NAA.
23. • Spectral changes in Epilepsy:
• Decreased NAA due to neuronal loss
or dysfunction.
• Increased choline , creatine
and lactate.
• Decreased GABA.
• MRS can help detecting the epileptic
focus for surgical treatment
of Epilepsy refractory to
medical treatment.
24. MRS AND
ALZHEIMER
DISEASE:
• Decreased NAA and GLX
• Increased myoinositol ( seen
specifically in Alzheimer dementia
but not in other types of
dementia) and choline peaks.
25. MRS changes in multiple sclerosis:
• Gradual decrease of NAA due to
gradual neuronal loss.
• Choline increase in acute lesion.
• Increased lactate and myoinositol
indicate active plaque.