History of Magnetic ResonanceFrom Magnetite to

Magnetic Resonance Tomograph

Jeannine Heller 23.04.2008

Magnetic Resonance

History of Magnetism History of Quantum Mechanics, Spectroscopy, Electronics & Hardware…

History of Magnetism

William Gilbert 1600: „De Magnete“→ earth is magneticadopted by Kepler, Galilei, Descartes

Hans Christian Øersted 1820: → electromagnetismadopted by Ampère, Faraday

- Two cultures: chinese & europeanChina 83 AD: magnetic spoon11th century: swimming needle for compass

- Pierre de Maricourt 1269:iron needles are oriented towards two points of a spherical magnetite→ concept of north and south pole

Michael Faraday 1831:established the basis for the magnetic field modelelectromagnetic induction -> power generation

James Clerk Maxwell: unified model of electromagnetism, light is an em wave~1850

Paul Langévin 1905: theory of para- and diamagnetismused by Weiss to explain ferromagnetism (1906)influenced Niels Bohr in the construction of his classical atom model (1913)

B

paramagnetic substance

Stern-Gerlach experiment 1922: wrong theory - right experiment!

undeflectedbeamB=0

defected beamd/dz B=1T/cm

47Ag: [Kr]4d105s1, l=0

discovery of the quantization of angular momentum,without realizing that this quantization was due to the spinning electron!

B

Old quantum view New quantum view(Bohr-Sommerfeld) (Heisenberg)

BB

J=1/2L=0, S=1/2

J=1L=1, S=0

M=+½

M=-½

B

M=+½

M=-½

M=+1

M=-1

M=0

M=-1

M=+1

M=0

zJJ = )1( +JJ

They believedthey had

They had

A memorial plaque mounted in February 2002 in Frankfurt

Uhlenbeck/Goudsmit 1925: discovery of the spin→ anomal Zeeman-effect (1896) could be explained(in fact Pauli had suggested a nuclear spin in 1924)

Goudsmit:„…luck plays a very, very great role…admittedly, there are cases likeHeisenberg, Dirac and Einstein, there are some exceptions. But for most of usluck plays a very important role and that should not be forgotten…“

1926: Schrödinger/Heisenberg formulation of qm replaced the old quantum theory

„History of Magentic Resonance“two groups:Bloch (Stanford University) Purcell (MIT)

But there were done experiments before:

Gorter 1936: tried to measure heat produced by resonant absorptionwith a calorimetric method� failed (but published)

Rabi 1937: atomic and molecular beam methods to measure sign of magnetic moment or ist magnitude

oven detect

A

B

C

Rabi‘s set up for beam experiments

Visit of Gorter 1937: transitions could be introduced more efficiently by resonant absorption of rfenergy in a homogeneous magnetic field placed between A and B

�C was changed!

• Magnets A, B, C inhomogeneous• Fields have same direction

BA BC

dzdB

dzdB

BB

rf (removable)

Resonance exp: C homogeneuos

� publication 1938first reported nuclear magnetic resonance signal (LiCl)

Rabi, Phys. Rev. 53 (1938) 318

� Nobel Prize 1944 for Rabi (only)

in the footer:

Coming back to Bloch and Purcell:They used different detection methods for the resonance signal

Bloch‘s idea:Macroscopic magnetization is tipped away fromeq position by resonant absorption from an rffield

Resulting magnetization, precessing about B0would induce an electrical signal in a coil placedalong x or y

B0

The experiment 1946:Two orthogonal coilsSample: liquid water

Packard‘s idea:Only one coil for emitting and receivingLooking for unbalances in the bridge circuit

Experiment 1945:Cavity resonant at 30 MHzVarying magnetic field1 kg Paraffin as sample

Purcell, Torrey, Pound Phys. Rev. 69 (1946) 37

Bloch, Hansen, Packard Phys. Rev. 70 (1946) 474

Bloch & Purcell: Nobel Prize in 1952

Zavoisky:tried to detect NMR signal in 1941, wasn‘t reproducible

successful detection of electron resonance: 1st reported observation of ESR in 1945

1950: E.Hahn First pulse NMR experiment1958: B.Mims First pulse EPR experiment1965: R.Ernst First FT NMR experiment1976: R.Ernst First 2D NMR experiment1986: J.Freed First 2D EPR experiment1994: Wrachtrup, Köhler, Groenen, Borzyskowski

First single molecule EPR experiment

Lauterbur Nature 242 (1973)190

The first MR Image in literature

In the early 1980s:12 machines, then it went like this:

> 1.5 T

< 0.5 T< 1.4 T

30 years

Damadian‘s MRI prototypein industiral metal style, 1977 today in ipod style

Future of MR

- higher magnetic fields

- use of high-temperature superconducting materials

- reliance on complex computational facilitiesand image processing procedures

- ?

- ?