Basic Physics: Pulse Sequences

Question 1

Do spin echo sequences rely more on RF pulses or gradient activations?

Answer 1

SE sequences rely more on RF pulses (heavy on RF)

Question 2

Are Gradient Echo Sequences heavier on RF pulses or gradient activations?

Answer 2

Gradient Activations

Question 3

Out of either Spin Echos or Gradient Echos, which uses a 180 degree refocusing pulse?

Answer 3

Spin echos use a refocusing pulse. Gradient echos only have a 90 degree or less initial pulse

Question 4

Which pulse sequence is heavy on gradients and uses rapidly changing phase and frequency gradient activations?

Answer 4

EPI sequence

Question 5

What is the purpose of RF pulses in MRI?

Answer 5

To increase the energy state of hydrogen atoms.

Question 6

Does the hydrogen contained in different tissues of the body relax at the same rate?

Answer 6

No. The hydrogen in different tissues relaxes at different rates. This is how we are able to produce contrast and see differences between tissues.

Question 7

Which physical gradient is activated at the head and foot of our patient?

Answer 7

Z Gradient