MRI

Question 1

Where does the signal come from in an MRI

Answer 1

The water in the body - specifically the hydrogen

Question 2

What is the larmour frequency

Answer 2

When the spin from the hydrogen atom processes at the speed proportionate to the magnetic field (the strength of the MRI). We want to tilt the axis of the spin in order to see the precession and measure it

Question 3

What does the coil of the MRI machine do

Answer 3

Oscillates the MF to tip the magnetisation out of equilibrium

Question 4

What causes the magnetisation?

Answer 4

More than half of the proton’s spin upwards and half spin downwards = spin excess

Question 5

What is the T1 and T2 rate dependent on?

Answer 5

Fat, bone, CSF and tesla power

Question 6

What does T2* do?

Answer 6

Lengthen the rate of decay as inhomogeneities such as blood and blood vessels can accelerate the loss of signal

Question 7

What mathematical tool creates the images?

Answer 7

Fourier Transform

Question 8

What parts of the brain does T2 weighted image contrast?

Answer 8

Bright = ventricles and CSF
Dark = white matter