brain scanning

Question 1

What are scanners used for

Answer 1

• investigate the structure
• diagnose medical conditions
• investigate without surgery

Question 2

Computed Tomography (CT)

Answer 2

• use radiation (x-rays) to produce cross-sectional images
• dense structures = absorb more (so darker)
• less dense structures = absorb less (so lighter)
• shows major structures –> but not function
• –> however if the patient has a diseased/damaged section of the brain alongside a loss of function the function of that section of the brain can be inferred
• e.g. damaged area and can’t see –> that area involved in vision

Question 3

Magnetic Resonance Imaging (MRI)

Answer 3

• use a strong magnetic field and radio waves to produce cross sectional images
• higher image quality for soft tissue and better resolution to distinguish between tissue types than CT
• –> so can clearly see difference between normal and abnormal brain tissues
• however same as CT can only work out brain function by looking at damaged areas

Question 4

Functional Magnetic Resonance Imaging (fMRI)

Answer 4

• like MRI but show changes as they happen
• measure activity in brain via blood flow/oxygenation+glucose
• -> (^activity = ^oxygenation+glucose/blood flow required for neurones)
• oxygenated blood reacts differently to magnetic fields than deoxygenated so the signal returned to the scanner is different –> so more active areas can be identified
• rich high detailed resolution
• unlike MRI and CT can show fucntion of brain bc they produce real time images
• behaviour can be carried out whilst in the scanner –> area of brain that lights up = responsible for that function

Question 5

Positron Emission (PET)

Answer 5

• show how active areas of the brain are
• through the use of a radioactive tracer that is introduced into the body and absorbed into the tissues
• scanner detects radioactivity of tracer –> build up radioactivity map of brain activity
• different tracers can label different things e.g. glucose –> show where all glucose is in the brain
• can both investigate structure and function in real time

Question 6

MRI medical diagnosis

Answer 6

• can be used to diagnose medical problems because they show damaged or diseased areas of the brain
• e.g. brain tumour/abnormal masses of cells
• tumour cells respond differently to magnetic fields so show up lighter in an MRI scan
• show size and location of tumour –> so can decide on effective treatments
• and infer which functions may be affected

Question 7

fMRI medical diagnosis

Answer 7

• show damaged/diseased areas and can study conditions/diseases that cause abnormal activity (some don’t have an obvious structural cause)
• e.g. can be taken before and after seizure –> area lit up after is responsible for seizures–> cam then identify most effective treatment

Question 8

PET medical diagnosis

Answer 8

• can show if brain areas are unusually active or inactive
• so useful in studying disorders that change the brains activity e.g. Alzheimer’s disease where the metabolism in certain areas of the brain is reduced
• -> can compare images of a healthy brain to a deficited one to see reduction