1. MRI: 造影原理

3. Quick Overview of MR Imaging Principle

4. From Pixel to Images

5. MR is very simple… U
65 %
H2O N S

6. Image Formation
MR Image
Fourier Transform
K-Space
Data Acquisition

7. Resonance & Relaxation
Data Acquisition
MR Signal
T1 & T2 Relaxation
Mxy Decay
Mz Recovery
Resonant RF Pulse

8. Magnetic Field Alignment of H Nuclei Spinning H Nuclei
( In Direction of Bo )
External Static Magnetic Field Bo
Spinning H Nuclei
( Random Directions )

9. In Magnetic Field Spinning H Nuclei Alignment of H Nuclei
( Random Directions )
External Static Magnetic Field Bo
Magnet
Alignment of H Nuclei
( In Direction of Bo )

10. Resonance & Relaxation
MR Signal Acquisition
Mxy Decay
Mz Recovery
Resonant RF Pulse
T1 & T2 Relaxation
RF Transmitting System
Gradient System
RF Receiving System

11. MR Image K-Space Data Acquisition Fourier Transform Computer
Array Processor

12. Patient + Magnet Without magnetic field : With magnetic field : B = 0x y
B = 0
M = 0 x y B M
No net magnetization
Low net magnetization

13. Slice Selection B = B0 + Gz * z Slice Excitation at 0 B  B0
Weaker Field
0
lower field, 0
higher field, 0
Stronger Field
0 z -z +z

14. Spatial Resolution within the Slice
Raw Data
p256f1
p256f256
p2f1
p1f1
p1f2
p1f256
(Phase und Frequency Encoding)

15. Raw Data Matrix (k-Space)ky
1               
2               
               
 N               
Raw data matrix or k-space is filled line by line by variation of the Phase Encoding Gradient kx
Line Information =
Frequencies of the
Readout Gradient

16. Fourier Transformation
Frequency
Phase x y

17. Zusammenhang von Orts- und k-Raum
Ortsraum
FFT
FFT-1

18. 3D Sequences 2D 3D No Slice Gaps Thinner Slices
Rectangular Slice Profiles
Postprocessing with MPR

19. Segmentierte k-Raumabtastungky
Aufteilung des k-Raums in Segmente
180°
180°
180°
90° RF kx Gs Gp Gr
ADC
Segment 1
Segment 2
Segment 3