MRI 3

Question 1

What are spin-echo pulse sequence?

Answer 1

spin echo pulse sequences are used to adjust tissue weighting

Question 2

What happens during spin-echo pulse sequences?

Answer 2

Two radiofrequency pulses are used to the excitation pulse at 90 degrees and the rephasing pulse at 180 degrees. During spin-echo two things affect the tissue weighting. TE & TR

Question 3

What is TE and TR?

Answer 3

Time to echo and time to repeat

Question 4

How is spin echo used to produce a T1 weighted image ?

Answer 4

a short TR and short TE maximises T1 imaging because the fat magnetisation recovers faster than water and a short amount of time between pulses gives the best contrast between fat and water where fat appears brighter than water

Question 5

How is spin echo used to produce T2 weighted images?

Answer 5

having a long TE and TR allows time for the transverse magnetization to relax before measuring the MR signal. this gives the best contrast between fat and water where water appears brighter

Question 6

How is spin echo used to produce proton density weighted images?

Answer 6

A long TR to minimise T1 contrast and a short TE to minimise T2 contrast