Question

1. After 90⁰ RF pulses spins lose phase coherence in a time related to:

a. T1

b. T2

c. T1/2

d. TE

e. TE/2

2. If a 90⁰ RF pulse has duration of t seconds, a 180⁰ RF pulse of the same intensity is likely to have duration of:

a) t/4

b) t/2

c) t

d) 2t

e) 4t

Answer 1

1.TE/2 , TE is the echo time,

After the 90degree RF pulse spins dephase, again after the 180degree RF pulse they are in phaae

2.2t

90 degree have 't' sec

180 degree have 'x' sec

So finding x= (180×t) /90

=2t