basics of magnetic resonance imaging (mri)epileptologie-bonn.de › cms › upload › homepage ›...
TRANSCRIPT
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