MRI & MRS

Question 1

MRI relies on the magnetic properties of what atom to produce images?

Answer 1

Hydrogen atom - i.e. proton

Question 2

The positive charge of a spinning proton produces what?

Answer 2

A magnetic moment, μ

Question 3

In a magnetic field, the magnetic moment of a proton processes at what frequency?

Answer 3

The Larmor frequency

Question 4

RF coils are used to transmit pulses of what electromagnetic frequency into the body?

Answer 4

Radiofrequency excitation pulses

Question 5

Name the main components of an MRI machine.

Answer 5

• Superconducting magnet
• RF coils
• Magnetic field gradients
• RF receiver
• Computer

Question 6

The intensity of an MR image depends upon what factors?

Answer 6

• Water content
• Tissue structure
• Blood flow
• Perfusion
• Diffusion
• Paramagnetics

Question 7

What is the T2 relaxation time?

Answer 7

• The T2 of tissue determines how quickly the MRI signal decays away after the RF pulse
• T2 is dependent on water mobility and increases with oedema and demyelination
• T2 is reduced by the presence of paramagnetic ions - Fe from blood breakdown products, Gd from contrast agents

Question 8

What is T1 relaxation time?

Answer 8

• k

Question 9

What is the taxi driver effect?

Answer 9

• Taxi drivers’ brains monitored over years
• Increase in hippocampal volume over time
• Neurogenesis proposed to explain need for increased capacity of spatial memory