Basics of magnetic resonance imaging (MRI)epileptologie-bonn.de › cms › upload › homepage ›...

Basics of magnetic resonance imaging (MRI)

Tobias Rudolph

14. Mai 18

Agenda

• Short overview 1. Classic view

– Basics (magnetic dipole momentum, top...) – Signal generation

2. Quantum mechanics 3. Bloch equation 4. Relaxation

– Spin-lattice-relaxation – Spin-spin-relaxation

5. Signals (Free induction decay)

14.05.2018 Basics of MRI 2

14.05.2018 Basics of MRI 3

http://www.medicalexpo.it/prod/canon-medical-system-europe/product-70354-428305.html

Information about MRI

• Body consists of water -> water contains protons -> proton has a spin

• Adventages:

– Not ionising

– 2D and 3D

– Free choice of section

– Change the contrast of soft tissue

14.05.2018 Basics of MRI 4

14.05.2018 Basics of MRI 5

14.05.2018 Basics of MRI 6

1. Classic magnetic top

Classical – Magnet in constant field

14.05.2018 Basics of MRI 7

S

𝐁

N

14.05.2018 Basics of MRI 8

Precession– Top in homogeneous field

Magnetic top in magnetic field

14.05.2018 Basics of MRI 9

Bz

𝐋

𝐦

Magnetic top in changing field

14.05.2018 Basics of MRI 10

14.05.2018 Basics of MRI 11

14.05.2018 Basics of MRI 12

Antenna

14.05.2018 Basics of MRI 13

Quadrature detector

14.05.2018 Basics of MRI 14

14.05.2018 Basics of MRI 15

2. Quantum mechanics – Nuclear spin

Gyromagnetic ratio

• Magn. dipole momentum:

• Lamor frequency:

14.05.2018 Basics of MRI 16

Quantisation

14.05.2018 Basics of MRI 17

L

Lz

Bolzmann statistic

14.05.2018 Basics of MRI 18

14.05.2018 Basics of MRI 19

14.05.2018 Basics of MRI 20

3. Bloch equation

Bloch equations

14.05.2018 Basics of MRI 21

Bloch equations after 90°-pulse

14.05.2018 Basics of MRI 22

Bloch equations - Solutions

14.05.2018 Basics of MRI 23

Spin-lattice-relaxation T1

14.05.2018 Basics of MRI 24

14.05.2018 Basics of MRI 25

Spin-spin-relaxation (dephasing / T2)

biggest B middel B

smallest B

ensemble with ω01 ensemble with ω02 ensemble with ω03

ensemble with ω03

ensemble with ω01

ensemble with ω02

Protons in fat

Protons in water

Protons in lactat

14.05.2018 Basics of MRI 26

Spin-spin-relaxation (dephasing / T2)

Some values

14.05.2018 Basics of MRI 27

14.05.2018 Basics of MRI 28

Magnetization after 90°- pulse

14.05.2018 Basics of MRI 29

https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance

Free- induction decay (FID)

14.05.2018 Basics of MRI 30

14.05.2018 Basics of MRI

Thank you for your attention

Sources

• http://www.rad-diak.de/untersuchungen/ganzkoerper-tumor-screening/

• https://www.trendsderzukunft.de/mrt-mehrfachscans-vermeiden-kontrastmittel-bleibt-im-gehirn/

• http://wswww.physik.uni-mainz.de/F-Praktikum/SS2010/PierreSissol.pdf

• O. Dössel „Bilgebene Verfahren in der Medizin“ 2000

14.05.2018 Basics of MRI 32