MRI Flashcards
what is the larmor equation?
frequency
Y= gyromagnetic ratio
b0= tesla of the magnet. (or the strength of the field at the level in the gradient- slice selection)
what is the gyromagnetic ratio of hydrogren at 1 tesla?
43MHz/T (42.5). 43x 1.5 for frequency at 1.5T
which of these will give good t1 contrast?
a) TE 15-20ms, TR 2000ms
b) TE 140ms, TR 2000ms
c) TE 10ms, TR 400ms
d) TE 1000ms, TR 300ms
C short TR and TE
which of these will give PD contrast?
a) TE 15-20ms, TR 2000ms
b) TE 140ms, TR 2000ms
c) TE 10ms, TR 400ms
d) TE 1000ms, TR 300ms
A short TE long TR
which of these will give good T2 contrast?
a) TE 15-20ms, TR 2000ms
b) TE 140ms, TR 2000ms
c) TE 10ms, TR 400ms
d) TE 1000ms, TR 300ms
B long TE, long TR
which of these will give good T2 contrast?
a) TE 15-20ms, TR 2000ms
b) TE 10ms, TR 400ms
c) TE 100ms, TR 2000ms
d) TE 1000ms, TR 600ms
C.
which of these will give good t1 contrast?
a) TE 30ms, TR 500ms
b) TE 1000ms, TR 300ms
c) TE 15-20ms, TR 2000ms
d) TE 140ms, TR 2000ms
A
define T1 recovery
the recovery of longitudinal magnetisation due to sin lattice relaxation after the RF excitation pulse is switched off. also called longitudinal recovery.
what is the T1 recovery time
time for 63% of the longitudinal magnetization to RECOVER in a tissue
what is t2 decay
the decay of coherent transverse magnetisation due to spin-spin relaxation after the RF pulse is switched off
what is the T2 decay time
the time it takes for 63% of coherent transverse magnetisation to decay
a T2 weighted sequence will have a…
a) long TE, long TR
b) short TE, short TR
c) short TE, long TR
d) long TE, short TR
A.
b is T1
c is PD
d is nothing
a PD weighted sequence will have a…
a) long TE, short TR
b) short TE, long TR
c) long TE, long TR
d) short TE, short TR
B
