Brain Scanning Techniques Flashcards
(11 cards)
what are the 3 brain scanning techniques?
CAT/CT Scan
PET Scan
FMRI Scan
How is a brain scan under gone?
The general procedure is the same for each of the brains scans:
The participant is typically lying down inside the scanner, keeping as still as possible. Detectors circle the participant’s head, obtaining information about one, thin ‘slice’ of the brain at a time. The detectors are then moved, and another ‘slice’ examined. A computer is used to translate the information from the detector into an image on a screen. By imaging multiple slices, a picture of the whole brain can be built up. (can also include a 3D image of the brain on the screen)
what is the key difference between the brain scanning techniques?
how the information is obtained. In a CAT/CT scan X-rays are used. In a PET scan, it is radioactive emissions from a tracer injected into the participant. In an fMRI scan it is the response of brain tissues to a strong magnetic field.
CAT/CT Scan AO1?
Produce a grey scale image of the brain structure, include bone, soft tissue and blood vessels. (DOES NOT CONVEY IMAGES OF BRAIN ACTIVITY OR FUNCTIONING.) so is useful in detecting brain damage or the location of tumours
non invasive, so nothing enters the body, although sometimes a radiographer will inject a dye to make certain features more prominent.
painless procedure, as it involves passing X-rays into the ear at multiple different angles (very low level of radiation)
the information is then passed to a computer to produce a detailed image of the brain
FMRI AO1
- designed in the 1990s to enable images of brain activity to be gathered without the use of radiation (The idea behind this technique is that brain activity is associated with blood flow in the brain)
- Utilises the bodies haemodynamic response – the areas of the brain that are the most active also use the most oxygen so blood is directed there
- involves having your head placed inside a very large, very powerful electromagnet. Inside the magnetic field, the nuclei within hydrogen molecules in water (from inside the brain) align themselves with the direction of the magnetic field, producing a structural image.
- Oxygen is carried to the brain in haemoglobin (red blood cells). When the bloody is oxygenated, it repels the magnetic field. However when it becomes deoxygenated (oxygen used up), it will follow the direction of the magnetic field which is then detected by the scanner
- The patient lies face-up on a flat surface and is rolled into a long tubular machine
- Inside the scanner, patents are given instructions: such as squeezing the left hand or thinking of certain words, increasing activity in specific parts of the brain increasing blood flow and oxygen
-This activity lights up on the images created by the scanner.
PET scans AO1:
- inject the patient in the vein in the arm/hand, with a radioactive tracer, fluorodeoxyglucose (FDG) 1 hour before the scan. patient cannot talk or move as it will affect where the FDG goes in the body
- Once the tracer has been absorbed into the bloodstream, a task is given to the patient in order to encourage activity.
- as the brain is working, the glucose will be used up and the FDG atoms starts to break down emitting positrons.
- During this process, gamma rays are produced and this is what the machine will detect
- High concentration of gamma rays will collect in areas of the brain with a high metabolic activity, as the most glucose will be used up there. This is pin pointing the location of the abnormality.
- areas of low metabolic activity will have less gamma rays, as less glucose was used
- A coloured image is produced: high levels of activity are shown with warmer colours like red, and lower levels are shown in cooler colours like blue.
scan takes 30-60 minutes.
Evaluate CT/CAT Scans as a brain scanning technique
G: (against) Due to the radiation that is exposed, they Cannot be used on pregnant women, or women who are breast feeding. it can harm the baby. (For) can be used across the wider population, (children, adults and elderly) and for various conditions (tumours or injuries) so the findings are representative.
R:They can also be easily repeated- following the same procedure, Time and number of scans.
V: (For) provided a detailed 3D structural image which helps diagnosis. Highly objective, no interpretation is needed, as you can easily identify the structural damage. (against) Does not pick up minor changes or soft tissue differences, doesn’t account for brain activity.
E: (against) Radiation can pose a threat to patients and can only be used a number of times. it is advised that they are only used when the possible benefits in relation to diagnosis outweigh the cost. Radiation can harm the patient: cause cell damage leading to various cancers, it is rare but allergic reactions can occur (For) non invasive
T/C: Quick and time effective (only takes around 5 minutes) and costs around £100 (cheaper than FMRI and PET)
Evaluate FMRI Scans
G: Some people may not be bale to have this scan: 1) Children- The Scanner is sensitive to movement die to the voxel size being small. Movement will cause the scanner image to blur. 2) Anyone who is claustrophobic or unnerved by confined spaces or loud noises may become quite stressed during the procedure (as they must lie flat and still in a large tube for the duration of the scan 3) Anyone that has metal surgical implants, or a cardiac pacemaker due to the high powered magnetic fields.
R: can be easily repeated, following the same procedure (time & number of scans produced)
V:Movement will cause the scanner image to blur. This will lead to an inaccurate estimate of the size and location of different brain areas. Objective interpretation of both structure and function (red = high activity, blue = low activity)
E: (against) may be stressful for patients, as they may feel claustrophobic or anxious (For) non invasive
T/C: time efficient as the scan takes 15-60 minutes, and costs around £500
Evaluate PET Scans as a brain scan:
G: not suitable for pregnant women
R: less consistent as reliability is die to timing the radioactive tracer, patient movement, or metabolic differences between individuals, so findings would be less consistent
V: Objective interpretation with red/blue concentration scale (quantitative data)
E: Invasive , as it requires patient to be injected with a radioactive tracer. Although it carries a low risk duet low levels of the substance involved
T/C: Costs around £500- £800) per scan, in total could be 3 million + the costs of running costs and facilities. Scan can take around 2-4 Hour so is not time efficient
Example research from using PET Scans:
Raine et al (1997) used PET scans to investigate differences between the brains or murderers and non-murderers. Using PET scans, they were able to map abnormal brain activity in the murderers’ group in areas of the brain associated with impulsivity and risk-taking behaviour, which may explain increased aggression. Raine highlights the importance of the pre-frontal cortex and amygdala.
Example research using FMRI scans:
Dustin Pardini et al used FMRI scans and found that men who had lower amygdala volume exhibited higher levels of aggression and violence.
