1. Computed Assisted Tomography Scan (CAT Scan)
CAT scans use a series of X-ray beams passed through the head, creating cross-sectional images of the brain showing the structure, but not the function.

2. How it happens
You need to remove all jewellery and glasses and all metal etc
You will be asked to lie on a scanner table
You must keep still during the procedure which takes about minutes
The staff leave the room and continue to talk to you through an intercom
The scanner table then moves through the scanner to take the first picture and rotates in small movements around your head to take further pictures
It is a painless procedure
You might need an injection or injections as part of the procedure. This will be discussed with you before your scan.
A dye is injected into the back of your hand or into the crook of your elbow and flows around your bloodstream to highlight the blood vessels in your brain or spine.
This helps to produce more detailed pictures.

3. Positron Emission Tomography (PET)
A scanner detects radioactive material that is injected or inhaled to produce an image of the brain.
Once in the bloodstream, it flows through the brain and oxygen and glucose accumulate in brain areas that are metabolically active.
As the glucose is used in the active parts of the brain, the radioactive material breaks down and gives off a neutron and a positron.
When a positron hits an electron, both are destroyed and two gamma rays are released.
Gamma ray detectors record the brain area where the gamma rays are emitted.
This method provides a functional view of the brain. E.g. language involves a number of areas in the brain. By asking someone to think of words, read words, or speak words researchers can find out which part of the brain works for a particular language function.

4. PET scans
They can be compared with ‘normal’ individuals to learn more about the illness
Epilepsy and other conditions can be studied by looking at blood flow in the brain.
They are mainly carried out for medical purposes, e.g. to check the damage made by a stroke
They can also be used to research how the brain works e.g. in individuals with schizophrenia

5. Positron Emission Tomography (PET)
Advantages
It is reliable – it can be repeated and the same results found – the same areas of the brain are consistently found for different activities
A reasonably non-invasive way of studding inside the brain (or body) – although the radioactive tracer is invasive
Ethical
Valid – the scan seems to measure what it claims to measure e.g. speech has been consistently found to be connected to Broca’s area

6. Positron Emission Tomography (PET)
Disadvantages
It is difficult to isolate different brain functioning precisely. E.g. people can read passages of text while being scanned but they would almost certainly be using other parts of their brain as well. It is valid to a point.
It is also expensive to use.
The use of the radioactive tracer is invasive so there are ethical issues – the researcher must follow ethical guidelines carefully (e.g. gained informed consent, having a good reason for doing the test.
The scan itself is claustrophobic – it must be carefully explained to the individual.

7. Magnetic Resonance Imaging (MRI)
MRI uses detection of radio frequency signals produced by displaced radio waves in a magnetic field. It provides an anatomical view of the brain.
The whole body is placed inside a tube, which can be claustrophobic.
The process is noisy but not painful.

8. MRI
MRI scans are affected by movement so the person has to keep very still.
MRI scans do not show activity to the same degree as PET scans, but they can measure blood flow.
Before an MRI scan, a dye called a contrast medium, is injected into the body to help show up body organs and relevant areas.

9. Magnetic Resonance Imaging (MRI)
Advantages
No X-rays or radioactive material is used.
Provides detailed view of the brain in different dimensions.
Safe, painless, non-invasive (apart from the injected dye).
No special preparation (except removal of all metal) is required from the patient.
It is valid because what is found in the scan is then often found in reality. They are accurate for checking abnormalities in the brain and the rest of the body.
More ethical – animals do not need to be used.
Replicable – it can be repeated and the same results found – the results can be checked by more than one person for objectivity.

10. Magnetic Resonance Imaging (MRI)
Disadvantages
MRI scans are stressful because an injection has to be given, they are extremely noisy and they can be claustrophobic. Stress should not be imposed on a patient without careful consideration of ethical guidelines and issues.
MRI scanning only measures particular things. There are for example clear images of soft tissue and body organs but brain activity is not measured. Knowledge from such scans is limited.

11. Functional Magnetic Resonance Imaging (fMRI)
Functional magnetic resonance imaging, or FMRI, is a technique for measuring brain activity.
It works by detecting the changes in blood oxygenation and flow that occur in response to neural activity – when a brain area is more active it consumes more oxygen and to meet this increased demand blood flow increases to the active area.
FMRI can be used to produce activation maps showing which parts of the brain are involved in a particular mental process.
For fMRI, your head may be placed in a brace designed to help hold it still. This brace may include a mask that is created especially for you. You may be given special goggles and/or earphones to wear, so that audio-visual stimuli (for example, a projection from a computer screen or recorded sounds) may be administered during the scan.

12. fMRI scans Advantages Disadvantages
Dispute over whether or not it actual measures what it claims to measure – e.g. increased levels of oxygen could be in preparation for neural activity, not because of it.
Very noisy. (small signals and lots of ‘noise’ make it difficult to pick up changes in oxygenated blood flow.
The images produced must be interpreted carefully, since correlation does not imply causality, and brain processes are complex and often non-localized.
Statistical methods must be used carefully because they can produce false positives.
It can noninvasively record brain signals without risks of radiation inherent in other scanning methods, such as CT or PET scans.
It has high spatial resolution. 2–3 mm is typical but resolution can be as good as 1mm.
It can record signal from all regions of the brain, unlike EEG/MEG which are biased towards the cortical surface.
fMRI is widely used and standard data-analysis approaches have been developed which allow researchers to compare results across labs.
fMRI produces compelling images of brain "activation".