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Brain Scanning - Coggle Diagram
Brain Scanning
CAT Scans
involves passing x-rays into the head - multiple beams are passed around the head from different angles
- procedure is painless but involves very low level exposure to radiation
can pose a risk to patients as there is exposure to radiation
- is advised that they are only used when the possible benefits in relation to diagnosis outweigh the potential risks
- less risky than exploratory surgery
- pregnant women are advised not to have CAT scans where possible
a detailed image of the structure of the brain is made
- useful for detecting areas of brain damage following an accident or a tumour
- doesn't give information on how the brain is functioning
CAT scans are very quick to conduct and give accurate detail of brain structure
- may help a surgeon make a better procedure plan
- may make procedures faster and more efficient, reducing risks associated with long duration under anaesthesia
Lusins et al (1980) - studied 50 patients with a CAT scan and psychological testing
- patients were alcohol and drug free, and without neurological or psychiatric disorders
- 58% of them had cerebral atrophy
PET Scans
involves injecting the patient with a small amount of radioactive material
- patients will be injected with fluorodeoxyglucose (FDG)
- a tracer substance where radioactive atoms are attached to glucose - brain uses the glucose as a form of energy
PET scans are more invasive than other techniques as they require the patient to be injected with a radioactive substance
- carries low risk due to very low levels of the substance
- it's not advisable for patients to have too many unless it's necessary
- unclear if there may be long term effects
once the tracer has been absorbed, a task is given to stimulate the brain and encourage activity
- as the brain works, the glucose will be used up and the radioactive atoms will start to break down, emitting positrons
- gamma rays are produced and the scaner picks these up
- high concentration of gamma rays will be found in areas of high activity - a lot of glucose will have been used there
can be useful for investigating areas of the brain that are not functioning normally, which could indicate damage or tumours
produces an image with different colours showing different levels of activity
- high levels of activity are shown by warmer colours e.g. red
- low levels are shown by cooler colours e.g. blue
can detect areas of damage by indicating which parts of the brain are showing abnormal levels of activity
- can help researchers to predict what kind of issues patients might face
fMRI
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involves having your head placed inside an electromagnet
- inside the magnetic field, the nuclei within hydrogen molecules in water align themselves with the direction of the magnetic field
- as neural activity increases in the brain, blood flow increases in the active areas to keep up with the demand for oxygen
- oxygen is carried to the neurons in haemoglobin within red blood cells which repels a magnetic force
- when deoxygenated the haemoglobin will follow the direction of the magnetic field and these changes are detected by the scanner to create an image
scanner sends information to a computer which creates a map of activation to show changing levels of neural activity in different brain areas as tasks are being completed