12 / 1311
21.05.14 |
StefanDelorme
Division ofRadiology
Suitable nuclei for in-vivo MR
Nucleus Spin
1
H
1/2
Water
31
P
1/2
ADP / ATP
23
Na 3/2
Na-K-Pump
14
N
1
13
C
1/2
19
F
1/2
Dental enamel
3
He
-1/2
129
Xe -1/2
21.05.14 |
StefanDelorme
Division ofRadiology
Precession
Magnetic
moment
Precession with ω
α
21.05.14 |
StefanDelorme
Division ofRadiology
Protons
65 %
water
1g (H
2
O) = 3.67
.
10
22
molecules
21.05.14 |
StefanDelorme
Division ofRadiology
Makroskopic magnetization
B
= 0
S
N
B = B
0
M
0
Σ
=
M
0
21.05.14 |
StefanDelorme
Division ofRadiology
Precession
B
0
ω = γ Β
0
21.05.14 |
StefanDelorme
Division ofRadiology
Resonant high-frequency excitation
•
Larmor frequency
•
ω
Precession frequency
•
External magnetic field, rotating with
ω
(
B
1
field)
•
Spins feel a quasi-static field
➡
Deflection by the flip angle α
x´
y´
z´
B
1
B
0
Flip angle
α