beskrivning och utvärdering av diffusions mr - Örebro universitet

Examensarbete 10p Örebro Universitet VT 2006
Innehåll
1. Inledning ........................................................................................................................................6
1.1 Bakgrund..................................................................................................................................6
1.2 Syfte.........................................................................................................................................6
2. Grunder inom Magnetic Resonance Imaging - MRI.......................................................................7
2.1 Spinn......................................................................................................................................... 7
2.2 Relaxation................................................................................................................................. 9
2.3 Pulssekvenser..........................................................................................................................11
2.3.1 Snittval............................................................................................................................ 11
2.3.2 Frekvenskodning.............................................................................................................12
2.3.3 Faskodning...................................................................................................................... 12
2.4 K-space och fouriertransform................................................................................................. 13
2.5 Spinnekosekvens.....................................................................................................................14
2.6 Gradientekosekvens................................................................................................................15
2.7 Echo Planar Imaging...............................................................................................................15
3. Hjärnans anatomi...........................................................................................................................17
4. Diffusions-MR...............................................................................................................................18
4.1 Inlednng.................................................................................................................................. 18
4.2 Teori........................................................................................................................................18
4.2.1 Diffusionsbildtagning......................................................................................................18
4.2.2 Diffusionssekvenser........................................................................................................ 18
4.2.3 b-värde............................................................................................................................ 19
4.2.4 Diffusionskoefficienten...................................................................................................20
4.2.5 Diffusionsriktning............................................................................................................ 21
4.3 Metod......................................................................................................................................23
4.4 Resultat................................................................................................................................... 25
4.4.1 Linjeplott.........................................................................................................................26
4.4.2 Histogram........................................................................................................................28
4.5 Diffusion med fantom.............................................................................................................29
4.5.1 Inledning......................................................................................................................... 29
4.5.2 Teori................................................................................................................................ 29
4.5.3 Metod.............................................................................................................................. 29
4.5.4 Resultat............................................................................................................................31
5 Diffusion Tensor Imaging – DTI....................................................................................................33
5.1 Inledning................................................................................................................................. 33
5.2 Egenvärden och egenvektorer.................................................................................................33
5.3 Anisotropisk och Isotropisk....................................................................................................34
5.4 Beräkning av Tensorn med ADC värden................................................................................35
5.5 Beräkning av medelvärdet med ADC värden.........................................................................38
5.6 Beräkning av Fraktionell Anisotropi (FA)..............................................................................39
6 Whole body diffusion MR..............................................................................................................40
6.1 Pulssekvenser..........................................................................................................................41
7. Slutsatser........................................................................................................................................42
8. Diskussioner.................................................................................................................................. 43
9. Referenser......................................................................................................................................44
10. MatLab kod................................................................................................................................. 45
5