This document explains MRI principles from spin precession to k-space and pulse sequence. This document presents the most important concepts of MRI for both physicians and college students. Some real-word MRI images were used to explain some techniques being used on MRI scanners on daily basis.
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MRI Principles
Wen-Yang Chiang
Oct 13, 2007
http://www.mrisprostatecancercenter.com/
dr-wheeler_the_prostate_center_hifu.html
http://www.med.umich.edu/opm/newspage/2004/b
raintumor.htm
Diffusion
Tractography
MRS
HIFU
Functional
MRI
Magnetic Resonance Imaging
Nuclear spinning
generates micro magnet
The alignment of nuclear
spin using external
magnetic field Apply RF pulse which is
close to Larmor frequency
Resonance
Transform the received
signal to image
MRI
Nuclear process within
external magnetic field
0B Provide spatial
information
www.e-mri.org
Basic Physics
Nuclear Spin
www.e-mri.org
Basic Physics
Processing & Larmor Frequency
00 B www.e-mri.org
Basic Physics
Net Magnetization
www.e-mri.org
Basic Physics
Excitation & Relaxation
www.e-mri.org
Signal
Formation
90 Pulse
www.e-mri.org
Signal
Formation
180 Pulse after 90 Pulse
www.e-mri.org
Signal
Formation
180 Pulse
www.e-mri.org
Signal
Formation
Relaxation
www.e-mri.org
Signal
Formation
Slice Selection
www.e-mri.org
Signal
Formation
Slice Selection
www.e-mri.org
Signal
Formation
Frequency Encoding
www.e-mri.org
Signal
Formation
Frequency Encoding
www.e-mri.org
Signal
Formation
Phase Encoding
www.e-mri.org
Signal
Formation
Phase Encoding
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Signal
Formation
Spatial Encoding
dx
dBg
B
x
Different g or t
dxextgS txgj )(),(
Signal Interpretation
Sinusoidal Encoding
greater gradient or longer t => higher frequency encoding
