Methodology: Scanning Techniques

Question 1

List the history of brain scanning developments.

Answer 1

1970s - CAT scans
PET scans
1990s - fMRI scans

Question 2

What does ‘CAT’ stand for?

Answer 2

Computerised Axial Tomography

Question 3

What are CAT scans typically used to study?

Answer 3

Areas of the brain and body that may be damaged or abnormal from cancerous cells.

Question 4

What images are produced by a CAT scan?

Answer 4

Generates 3D x-ray images of the brain/body.

Question 5

How do CAT scans work?

Answer 5

• Multiple x-ray beams are passed around the part of the body being scaned from different angles
• The x-rays are absorbed by different densities of bone and tissue, showing density on the image produced
• This information is then interpreted by a computer to form an image
• Dye is sometimes injected to distinguish the normal tissue from abnormal

Question 6

How long do CAT scans typically take?

Answer 6

15-30 mins

Question 7

What is the patient required to do during a CAT scan?

Answer 7

Lie still on a platform.

Question 8

Identify a study that used a CAT scan.

Answer 8

Lusins et al (1980) used a CAT scan to investigate alcoholism on the brain in 50 patients who were alcohol-free at the time and found 58% of them had cerebral atrophy (the loss of neurons, etc).

Question 9

Evaluate 2 strengths of CAT scans.

Answer 9

1) High validity due to scans taking place in controlled conditions of labs therefore EVs are controlled for and a cause and effect relationship can be established
2) Less harmful to ppts compared to PET scans which involved injecting the patient with a radioactive glucose tracer therefore CAT scans have reduced stress

Question 10

Evaluate 2 weaknesses of CAT scans.

Answer 10

1) Limited in their use due to only detecting abnormal cells in the body and brain and doesn’t look at brain activity unlike PET and fMRI scans whcih offer more insight in to more modern methods
2) Potentially harmful to patients as they expose people to radiation and as such are limited in their use as would not be suitable for a pregnant women

Question 11

What does ‘PET’ stand for?

Answer 11

Positron Emission Tomography

Question 12

What are PET scans typically used to study?

Answer 12

Areas of the brain that are damaged in lacking of activity.

Question 13

What images are produced by a PET scan?

Answer 13

• A colour image showing levels of activity
• Red indicates high levels of activity
• Blue indicates low levels of activity

Question 14

How do PET scans work?

Answer 14

• Patients are injected with the radioactive glucose tracer FDG
• The levels of activity in the brain are assessed via the glucose uptake of areas
• The glucose atoms in the tracer then breakdown after absorption producing gamma rays that are picked up
• High concentration of gamma rays indicates high activity

Question 15

How long do PET scans typically take?

Answer 15

15-35 mins

Question 16

What is the patient required to do during a PET scan?

Answer 16

• To be injected with the radioactive substance

- Place their head in a tubular scanner

Question 17

Identify a study that used a PET scan.

Answer 17

Raine et al (1997) used a PET scan to investigate whether the brain activity of murderers pleading NGRI was different to non-murderers and found lower glucose uptake in certain areas that can be linked to aggression.

Question 18

Evaluate 2 strengths of PET scans.

Answer 18

1) High in reliability due to scans being a standardised procedure in controlled conditions therefore can be replicated quickly and compared easily with the objective images
2) Highly scientific due to reducing behaviour down to abnormalities in the brain and activity of certain areas with metabolic rate therefore each area is measurable

Question 19

Evaluate 3 weaknesses of PET scans.

Answer 19

1) Low ecological validity due to being carried out in a controlled artificial setting which is not natural to the patient therefore their brain activity may not reflect that of real life
2) Low ethics due to involving a radioactive injection that can severely distress patients as well as confining the person to a small space for an extended period of time for those with claustrophobia
3) Limited in its use due to involving a radioactive substance that is harmful to pregnant women therefore not suitable for some people

Question 20

What does ‘fMRI’ stand for?

Answer 20

Functional Magnetic Resonance Imaging

Question 21

How do fMRI scans differ from MRI scans?

Answer 21

They look at activity by measuring blood flow rather than the structure of grey matter in the brain that MRI scans measure.

Question 22

What are fMRI scans typically used to study?

Answer 22

Activity in the brain based on blood flow.

Question 23

What images are produced by an fMRI scan?

Answer 23

Black and white with colour of places with activity.

Question 24

How do fMRI scans work?

Answer 24

• A magnetic field is passed through the patients head
• Nuclei within hydrogen molecules align with this magnetic field
• When an area of the brain is more active it will consume more oxygen so will therefore have a higher concentration of blood
• Haemoglobin in blood repels the magnetic field being diamagnetic and when full of oxygen follows the field being paramagnetic
• A scanner detects this change to create an image of a map of activation on a computer

Question 25

How long do fMRI scans typically take?

Answer 25

30-40 mins

Question 26

What is the patient required to do during an fMRI scan?

Answer 26

• Lie completely still on a slab with their head in a powerful electromagnet

Question 27

Identify a study that used an fMRI scan.

Answer 27

Li et al (2013) used fMRI scans to investigate how heroin affects the brain and found that PCC area of the brain was activated by images of drug paraphernalia showing its role in craving and drug-seeking behaviour.

Question 28

Evaluate 2 strengths of fMRI scans.

Answer 28

1) High inter-rater reliability due to producing quantitative data of an image that can be objectively interpreted by multiple researchers
2) High ethics compared to other scans as doesn’t expose the patient to radiation or cause distress from an injection meaning they are more useful

Question 29

Evaluate 3 weaknesses of fMRI scans.

Answer 29

1) Low validity due to being in a lab condition that is an unnatural setting for the ppt in which they cannot move therefore their brain activity may not reflect real life situations where they are more comfortable
2) Low ethics due to involving the patient being in a confined space with distracting loud noises that can cause distress through claustrophobia
3) Limited use due to not having as much detail as PET scans that can look at receptors at the synapse or be used on people with pacemakers and tattoos