Magnetic Resonance Imaging: A Historical and Technological Overview - Prof. John G. Georgi, Study notes of Mechanical Engineering

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ME 498

April 3, 2007

Magnetic Resonance Imaging --Basics John G. Georgiadis Mechanical Science & Engineering

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Outline { Background: z NMR Physics z Relaxation phenomena and kinetics z Space encoding { Applications: z Non-clinical Applications z Brain z Other organs z Scanners and safety

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Chronology ( *denotes Nobel Prize related to NMR) 1921 *Stern & Gerlach discover nuclear

spin

1924 de Broglie publishes his

wave theory of matter

1925 *Pauli introduces the

exclusion principle

1926 Fermi links

spin with statistics

1927 *Thomson observes

electron diffraction

1928 Hartree develops his

approximation

“^ London & Heitler apply quantum mechanics to chemical bonds 1934 Fermi theorizes

weak interactions

1935 Yukawa theorizes

strong interactions

1937 *Rabi does first

NMR experiments

1939 Hahn & Strassman observe

fission

1946 *Bloch & *Purcell make

NMR^ as a practical instrument

“^ First electronic computer built at University

of^ Pennsylvania

1948 Feynman, Schwinger & Tomonaga develop

QED

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(^1950) *denotes Nobel Prize related to NMR Chronology (cont) Hahn^

NMR spin echo discovered/self diffusion

1951 Suryan 195419591959196019601965196519661969197319731974197419771982198419861986198619861988

NMR measurement of coherent motion of liquid

Carr &^ *^ Purcell

NMR even echo re-phasing Bowman & Kudvavcev

NMR washout flow meter Singer^

NMR/first blood flow measurement Singer^

NMR tagging velocimetry Hahn^

NMR phase shift to measure slow motion/theory Zhernovoi & Latyshev

NMR pulse frequency flow (tagging) measurement Stejkal & Tanner

NMR pulse gradient/incoherent motion – diffusion

*^ Ernst & Anderson

NMR Fourier Transform Spectroscopy Packer^

NMR phase/diffusion vs. coherent velocity

*^ Lauterbur (UIUC)

MRI projection-reconstruction discovered/2-D image of liquid

*^ Mansfield^

NMR with magnetic field gradients/spatial structure of solid Lauterbur^

MRI first in-vivo image Garroway^

MRI 90°-t-90°

/first (slow) velocity profile

Mansfield^

MRI fast Fourier space scanning (EPI) Moran^

MRI Fourier phase encoding velocimetry/theory Redpath et al.

MRI Fourier phase encoding/rotating phantom Caprihan et al.

NMR 1-D phase encoding/ Poiseuille and plug flow Axel et al.^

MRI time-of-flight/flow displacement in a slice Dumoulin & Hart

MRI bipolar phase encoding with subtraction /angiography Haase et al.^

MRI gradient echo (FLASH) imaging Hennig et al.^

MRI Fast Spin Echo (FSE) imaging

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NMR History {^ 1976:

Lauterbur:

First NMR image

of sample tubes in a chemicalspectrometer { 1981:

First commercial scanners <0.2T { 1985:

1.5T scanner {^ 1986:

Rapid developments in SNR, resolution

etc

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Image Contrast {^ Proton, T1-, T2-weighted imaging {^ Diffusion imaging {^ Perfusion Imaging {^ Imaging of Blood Flow {^ Imaging of Blood Oxygen Level {^ Magnetization Transfer {^ Etc ..

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MRI Today 10,000 MRI scanners worldwide Establish modality in diagnosis/staging of manydiseases, such as Cancer, Stroke. Multi-billion dollar business (GE, Philips, Siemens) Many new applications are under investigation(ISMRM ~4,000, RSNA ~ 50,000)Cardiac MRI, interventional MRI etc.

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NMR signal …predominantly from protons Isotope^ m

s^

μ^ g

NAbundance- 27^ (10^ )^

NMR Sensitivity

ω^ /2 π^0 (MHz)

1 1/2, -1/2H^

5.^ 5.^ 99.^

=^

42.

2 1, 0, -1H^

.^ 2.^

.02*^

.^

3.

13 1/2, -1/2C^

1.^ 2.^

1.11*^

.^

4.

19 1/2, -1/2F^

5.^ 2.^

probe^

.^

18.

31 1/2, -1/2P^

2.^ 2.^

probe^

.^

8.

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• ω = γ B
  • ω = Larmor frequency

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Proton Relaxation in Solution

T1 T

310 -1 10 -5 10 -9 10 -11^10

-8^10 -5 10 sec

τ(sec)cor ωτ=1cor^0

B

B^0 B^0 τcor

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