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Magnetic resonance spectroscopy
Magnetic resonance spectroscopy (MRS) is a noninvasive imaging technique that assesses metabolic changes in brain tissue, aiding in the diagnosis and monitoring of conditions like tumors and epilepsy. It utilizes different metabolites to differentiate between normal and abnormal tissues, allowing for early detection and evaluation of disease progression and treatment response. MRS is particularly valuable in understanding conditions like Alzheimer's disease and multiple sclerosis through its ability to measure various biochemical markers.
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Magnetic resonance spectroscopy
- 1. BY HAIDY ELBIADY. IMG,WASHINGTON UNIVERSITY OF HEALTH AND SCIENCE. MAGNETIC RESONANCE SPECTROSCOPY(MRS)
- 2. DEFINITION • MRS isa 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'tbe 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.
- 4. MRI VERSUS MRSNORMAL VIEW • MRI • MRS
- 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 • MRScharts 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 measuresabout 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.
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- 10. METABOLITES DETECTED BYMRS • 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.
- 17. METABOLITES DETECTED BY MRS Glutamate/Glutamine:(GLX) Resonates at2.05 and 2.50 ppm. Glutamate is an excitatory neurotransmitter. Glutamine increases in hepatic encephalopathy. Alanine : increases in meningioma.
- 19. APPLICATIONS: 1)Study of intracranialspace 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 TUMORSTAGING: 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 BRAINTUMORS 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 upand 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 changesin 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: • DecreasedNAA and GLX • Increased myoinositol ( seen specifically in Alzheimer dementia but not in other types of dementia) and choline peaks.
- 25. MRS changes inmultiple sclerosis: • Gradual decrease of NAA due to gradual neuronal loss. • Choline increase in acute lesion. • Increased lactate and myoinositol indicate active plaque.
- 26. MY RESEARCH REFERENCES: •https://radiopaedia.org/articles/mr-spectroscopy-1?lang=us •https://www.slideshare.net/NeurologyKota/imaging-mrspectroscopy •http://spinwarp.ucsd.edu/NeuroWeb/Text/mrs-TXT.htm •https://en.wikipedia.org/wiki/In_vivo_magnetic_resonance_spectroscopy •https://www.youtube.com/watch?v=l3ZR5Y-Wkpw •https://www.youtube.com/watch?v=FgKxc9mh8pw •https://www.youtube.com/watch?v=TJhVotrZt9I •https://www.youtube.com/watch?v=x_uAtZlKllA •https://www.slideshare.net/phongkhamsieuamannhi/mrs-23104453 •https://www.eurekalert.org/multimedia/pub/137546.php •Case courtesyof Dr Gagandeep Choudhary, <a href="https://radiopaedia.org/">Radiopaedia.org</a>. From the case <a href="https://radiopaedia.org/cases/11051">rID: 11051</a> •Case courtesy of Dr Ahmed Abdrabou, <a href="https://radiopaedia.org/">Radiopaedia.org</a>. From the case <a href="https://radiopaedia.org/cases/36657">rID: 36657</a> •https://www.brighamandwomens.org/radiology/research/spectroscopy/about-spectroscopy •https://www.researchgate.net/figure/Normal-brain-curve-from-proton-magnetic-resonance- spectroscopy-of-the-brain-showing_fig1_8682592 •https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.researchgate.net%2Ffigure%2FH- MRS-image-showing-an-increased-peak-of-choline-with-a-mean-chol-cr-ratio-of-229- as_fig2_7985635&psig=AOvVaw1U9VCArT6fBjSFQ1xLU7Z2&ust=1602531956609000&source=images &cd=vfe&ved=0CAIQjRxqFwoTCKigz_WmrewCFQAAAAAdAAAAABAD
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