Brain Scanning

Question 1

Brain scans

CAT/CT scans A01

Answer 1

• Used to take images of any part of the body
• Scans of the brain involve passing X-rays into the head, unlike standards X-rays there are multiple beans passed around the head, from different angles to gather more information
• Information from the multiple beams is interpreted by a computer and detailed image of the structure of the brain can be seen
• This is useful for detecting area of brain damage following an accident or the positioning of tumours in the brain, but doesn’t give information on how the brain is functioning eg activity

Question 2

Brain scans

PET scans A01

Answer 2

• Looks at different levels of metabolic activity in the brain
• The cells need glucose for energy, and brain neurons use glucose from the blood stream as a source of energy
• By injecting a person with glucose, mixed with a small amount of a radioactive compound it is possible to see how much glucose each area of the brain is using
• Measure the amount of radioactivity,sending information to a computer, creating cross sections of the brain, showing the area using different amounts of glucose as different colours
• The harder an area works, the more glucose is needed, shows up as more radioactive
• Used for comparison (SZ), epilepsy, blood clots, brain tumours and investigating brain area functions

Question 3

Brain scans

fMRI scans A01

Answer 3

-Patients lie in a round tunnel surrounded by a large magnet generating a powerful magnet field
-Structure; when the part to be studied is placed inside the strong magnetic field it affects the magnetic nuclei of atoms, which become aligned with the direction of the field
-The stronger the field= the greater the degree of alignment
-Causes the magnetic signals from individual nucleus to add up coherently in a signal which can be measure, in fMRI this comes form the hydrogen nuclei in water (H20)
-This varies based on surroundings, meaning we can discriminate between grey matter, white matter and cerebral spinal fluid in structural images of the brain; allows us to see the tissues in the brain
-Activity; oxygen is delivered to neurons by hemoglobin in red blood cells. Increased neuronal activity means increased demand for oxygen and increased blood flow to regions of increased neural activity
-Hemoglobin= diamagnetic when oxygenated
= paramagnetic when deoxygenated
-Leads to differences in MR signal of blood, depending on the degree of oxygenation
-Since this varies according to levels of neural activity- these differences c an be used to detect brain activity= BOLD imaging