Imaging for Physicists

Gradients

B γ

0 ω =

• Recall that the resonant frequency is proportional to field strength

0

dy dB G 0 dz dB G 0 dx dB G 0

=

x

• Magnetic gradient changes B 0 strength over distance • In MRI a linear gradient changes the resonant frequency in a given direction field

=

y

(

) x xG B + =

=

ω

γ

z

0