Neuroimaging Methods: Visualising the brain & its injuries
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Transcript of Neuroimaging Methods: Visualising the brain & its injuries
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Neuroimaging Methods:Visualising the brain & its injuries
• Structural (brain structure)– X-rays – CT (Computer Tomography) – MRI (Magnetic Resonance Imaging)
• Functional (brain function)– Blood flow (PET/SPECT/fMRI). – Neuron’s electrical responses (EEG/ERP)–
Special thanks to Chris Rorden, U. South Carolina
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• X-ray tube projects through head• Detector plate measures transmission of X-rays
– Bone relatively opaque to X-rays– Soft tissue relatively transparent
• Use:– broken bones– Angiography
• Not good for much else
Structural: X-rays
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Structural: CT scans
Uses:– Stroke – Brain tumors (larger than 2-4 mm)– Enhanced with contrast material– Subdural Hematoma – Evaluation of traumatic Head Injury
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CT scan
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MRI• Magnetic resonance imaging • Does not expose individual to X-rays
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MRI scans
Healthy enlarged ventricles MCA infarct
& wide sulci
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Types of MRI scan
• T1 (anatomical): – fast to acquire, – good detail (e.g. white and gray matter).
• T2 (pathological): – slower to acquire, thus worse resolution. – Excellent for finding lesions.
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• PET (Positron Emission Tomography
• SPECT (Single Photon Emission Computerized Tomography)• Radioactive oxygen isotope injected into blood • Brain regions that use oxygen emit more positrons
Functional imaging: Measures brain activity
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functional: fMRI• fMRI: Functional Magnetic Resonance Imaging
- Increase activity in certain brain area- Blood vessels dilate - The % of Oxygen in the blood in that area is changed- The MR machine registers that
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Functional: Electroencephalogram (EEG)
• Measures electrical activity • • When neurons fire, they create electical dipoles.• Neurons aligned perpendicular to cortical surface.
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Event related potentials (ERPs)• ERPs are a type of EEG
– Continuously collect EEGs– Present many trials of stimuli (words: neutral vs. offensive)– Compute average brain response to stimuli
• Good temporal resolution (when activity starts happening).
• Poor Spatial resolution
Time (ms)0 100 200 300
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Sign
al
V neutral
‘rape’
http://brainserver.psych.indiana.edu/
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In sum,
• Structural (brain structure)– X-rays – CT (Computer Tomography) – MRI (Magnetic Resonance Imaging)
• Functional (brain function)– Blood flow (PET/SPECT/fMRI). – Neuron’s electrical responses (EEG/EEG)– Neuron’s magnetic responses (MEG)