Biopsych - Lecture 4 (Commonly used tools)

Angiogram

• detailed pictures of the blood vessels in the brain

  • Useful for identifying: narrowing arteries, blood clots, aneurysms, displacement of vessels due to tumor 

Computed Tomography (CT Scan)

• Looking at cross-sectional x-rays 

• Useful for: Detecting injuries (complex fractures, internal bleeding, acute urgent situations (for example, getting into a car accident and you’re unconscious) 

• Diagnosing cancers 

• Guiding medical procedures (biopsies)

• Monitoring progress of treatment 

Downsides: Radiation (but small amounts) 

MRI

Higher resolution than CT so it’s better for visualizing soft tissues (brain, spinal cord, ligaments, etc.) 

• How it works: Measures waves emitted by hydrogen atoms 

• When you lie down in the scanner, the protons in the body line up in the same way, and then you get a short burst of radio waves that knock the protons out of alignment. And then you stop the radio wave, this sends out radiofrequency signals that are detected by the scanner. 

• Different types of tissues contain different amounts of water, and the protons realign at different speeds and produce distinct signals. 

• Downsides: relatively slow, can’t have ferrous (iron) metal implants, very noisy, confined space 

•  BASICALLY: It is measuring how protons move and that protons move at different speeds depending on how much water 

Positron Emission Tomography (PET) Scans

• Highlights brain activity 

• Injecting radio-labelled 2-deoxyglucose 

• Active neurons take up the tracer (so they’re metabolically active)

• Useful for detecting metabolic activity 

• Useful for Alzheimer's disease, stroke, cancers, etc. (Just looking to see if they’re functioning the way they’re supposed to)

• PET scans are looking at glucose uptakes 

Functional MRI  

• Looking at the fact when brains are active, they need to use oxygen (they’re looking at oxygen levels)

• Oxygenated blood has different magnetic properties than deoxygenated blood

• This alters the radio frequency waves omitted by H+ ions

• Signals are called BOLD signals - Blood oxygen level dependent signals 

• Pro: No radioactivity

• Cons: Too slow to catch some neural activity

Diffusion Tensor Imaging (DTI) 

• Images axonal tracts (It wants to look at where are the axons are going)

• Useful for tracking neurodegenerative diseases (for example: multiple sclerosis)

• Based on rapid diffusion of water molecules (looking to see where is the water molecule moving, how is it moving along the axon)

• Allows viewing of neuronal interconnectivity (Basically that shows us how these neurons are connecting to other parts of the brain)