Neuroimaging Flashcards
Who discovered MRI?
Felix Block and Edward Mills Purcell
What year was MRI discovered in?
1947
In which year were the first clinical MRI images obtained?
1977
Which molecule does MRI rely upon for imaging?
Water
What type of energy is released to excite the protons in water in the body?
Radiofrequency pulse
What does T1 refer to?
Longitudinal relaxation and realignment with magnetic field following radiofrequency pulse disturbance
What does T2 refer to?
Transverse relaxation and the resumption of protons spinning around their own axis
In T2 weighted images, what appears brighter?
Water componenets
What are T2 weighted images useful for clinically?
Detecting pathology
In T1 weighted images, what appears brighter?
High-fat content
What are T1 weighted images useful for clinically?
Analysing anatomy
How is a 3D image of the brain constructued?
Images from multiple planes are reassembled digitally
How are different planes of view obtained in MRI?
By passing radiofrequency pulse through the head at different angles
What is the average strength of an MRI scanner?
1 to 3 Tesla
How can the study of vascular structures be enhanced?
Use of Gadolinium contrast
What is gadolinium contrast used for?
Enhancing vascular structures
How is gadolinium administered?
Intravenous infusion
How does gadolinium perform in a magnetic field?
It is paramagnetic, it only has a magnetic field when in a strong magnetic field but does not retain any permanent magnetic properties
How do structural and functional MRI differ?
Structural studies anatomy
Functional studies brain function
What does fMRI detect?
Changes in blood oxygen level (BOLD)
How can blood oxygen level be detected under MRI?
Deoxyhaemoglobin is paramagnetic but oxyhaemoglobin is not
What are limitations associated with fMRI?
Indirect measure of activity
Assumes that change in blood flow is synonymous with activity
There is a delay between neuronal activity and blood flow response
Low temporal resolution
Cannot differentiate between axonal or dendritic activity causing BOLD signal
How can fMRI be used in clinic?
Diagnosing brain death
Detecting consciousness in comatose patients
How can fMRI be used in pharmacological research?
Can measure efficacy of drugs via titrating dosages and imaging
How does positron emission tomography (PET) work?
Body is abundant in elements that have positron-emitting forms. Radioactive isotopes for these elements are injected, they have a short half-life and emit positrons that collide with electrons, resulting in photon emission that is detected by the scanner
What is PET useful for assessing in clinic?
Molecular function and activity
What does diffusion weighted MRI show?
Differentiation between abnormal diffusion of protons in damaged neurons
What are diffusion weighted images useful for assessing?
Damage to tissues (after stroke)
What is a limitation of PET?
It is an indirect measure of brain activity
