Compre reviewer Flashcards
a continuously changing flow of electrons that alternates its polarity at a periodic rate.
AC ( alternating current)
the total number of independent data samples in the frequency (f) and phase (f) directions.
ACQUISITION MATRIX
the process of measuring and storing image data.
Acquisition
the period of time required to collect the image data. This time does not include the time necessary to reconstruct the image.
ACQUISITION TIME
large network of interconnecting blood vessels at the base of the brain that when visualized resembles a circle.
CIRCLE OF WILLIS
the act of maintaining a constant phase relationship between oscillating waves or rotating objects.
COHERENCE
a variation in the nominal Larmor frequency for a particular isotope within the imaging volume. The amount of shift introduced is directly proportional to the strength of the magnetic field, and is specified in parts per million (ppm) of the resonant frequency.
CHEMICAL SHIFT
an artifact introduced into images by interference between adjacent slices of a scan. This artifact can be eliminated by limiting the minimum spacing between slices.
CROSSTALK
a type of magnet that utilizes coils of wire, typically wound on an iron core, so that as current flows through the coil it becomes magnetized.
ELECTROMAGNET
an induced spurious electrical current produced by time-varying magnetic fields. Eddy currents can cause artifacts in images and may seriously degrade overall magnet performance.
EDDY CURRENT
a fast spin echo pulse sequence characterized by a series of rapidly applied 180° rephasing pulses and multiple echoes, changing the phase encoding gradient for each echo.
FAST SPIN ECHO (FSE)
This was a fundamental discovery in physics.
Rotating Magnetic field
Who discovered rotating magnetic field
Nikola Tesla
what year tesla discovered rotating magnetic field
1882
best known for many revolutionary contributions in the field of electricity and magnetism in the late 19th and early 20th centuries.
Nikola Tesla
Recommended limit for constant human exposure
2mG
The CGS unit for magnetic induction was named gauss in his honour
Carl Friedrich Gauss
centimeter gram second system of units
CGS
best known for initiating the investigation of Fourier series and their application to problems of heat flow.
Jean Baptiste Joseph Fourier
s a mathematical procedure to separate out the frequency components of a signal from its amplitudes as a function of time
Fourier Transform
developed the equation that the angular frequency of precession of the nuclear spins being proportional to the strength of the magnetic field.
Sir Joseph Larmor
what year he proposed a quantum spin number for electrons
1924
proposed a quantum spin number for electrons
Wolfgang Ernst Pauli
proposed the Pauli exclusion principle, for which he received the Nobel Prize for Physics in 1945.
Wolfgang Ernst Pauli
What year he proposed the Pauli exclusion principle, for which he received the Nobel Prize for Physics in 1945.
1925
First to recognize the existence of the neutrino
wolgang
fermions are particles which obey Fermi-Dirac statistics; they are named after
Enrico Fermi.
states that no two identical fermions may occupy the same quantum state simultaneously.
Pauli exclusion principle
introduced the concept of a spinning electron, with resultant angular momentum and a magnetic dipole moment arising from the spinning electrical charge
George Eugene Uhlenbeck
succeeded in detecting and measuring single states of rotation of atoms and molecules, and in determining the mechanical and magnetic moments of the nuclei.
Isidor Isaac Rabi
Published “A New Method of Measuring Nuclear Magnetic Moment” in 1938, where the first MR signal from LiCl was reported.
Isidor Isaac Rabi
First to demonstrate the phenomenon of paramagnetic relaxation.
Cornelius Jacobus Gorter
discovered electron paramagnetic resonance in 1944.
Yevgeny Konstantinovich Zavoisky
In September 1937, he and his co-worker Broer, reported unsuccessful attempts to observe nuclear magnetic resonance in pure crystalline materials.
Cornelius Jacobus Gorter
In 1937, He observed the quantum phenomenon dubbed nuclear magnetic resonance (NMR). He recognized that the atomic nuclei show their presence by absorbing or emitting radio waves when exposed to a sufficiently strong magnetic field.
Isidor I. Rabi
In 1946 , They discover magnetic resonance phenomenon.
Felix Bloch and Edward Purcell
In 1946 , They discover magnetic resonance phenomenon.
Felix Bloch and Edward Purcell
developed instruments, which could measure the magnetic resonance in bulk material such as liquids and solids.
Felix Bloch and Edward Purcell
Together with his colleagues Torrey and Pound, prepared a resonant cavity to study the absorption of RF energy in paraffin.
Edward Mills Purcell
Nuclear induction.
Together with his colleagues, did an experiment measuring an electromotive force resulting form the forced precession of the nuclear magnetization in the applied RF field.
Felix Bloch
The year often regarded to as the birth of MR
1952
Some book puts the year commonly regarded as the year in which MR was discovered as
1946
creates a one-dimensional MR image.
Herman Carr
The strength of a magnetic field is measured in
Tesla or Gauss Units
The stronger the magnetic field, the stronger the amount of radio signals which can be elicited from the body’s atoms and therefore the _______.
higher the quality of MRI images
further developed the utilization of gradients in the magnetic field and the mathematically analysis of these signals for a more useful imaging technique.
Peter Mansfield
First to demonstrate clinical MR images of a human finger using his technique.
Peter Mansfield
was the first ultra high-speed imaging technique.
EPI (echo-planar imaging)
Showed how signals can be mathematically analyzed which later gave way to EPI technique in 1977
Peter Mansfield
development of radionuclide imaging, magnetic resonance imaging (MRI) and, in particular, positron emission tomography (PET).
John Mallard, James Hutchinson and the Aberdeen Prototype
Originated the “spin-warp” method of spatial localization for MRI
John Mallard, James Hutchinson
demonstrated with his NMR device, that there are different T1 relaxation times between normal and abnormal tissues of the same type, as well as between different types of normal tissues
Raymond Vahan Damadian
discovered that hydrogen signal in cancerous tissue is different from that of healthy tissue because tumors contain more water.
Raymond Vahan Damadian
first MR scanner called
Indomitable
which manufactured the first commercial MRI scanner in 1980.
FONAR Corporation,
Fonar went public in
1981
Raymond Damadian applies for a patent, which describes the concept of NMR being used for above purpose. He illustrates major parts of MRI machine in his patent application i_____________.
1972
produced the first NMR image. It was of a test tube.
Paul Lauterbur
described a new imaging technique that he termed Zeugmatography
Paul Lauterbur
referred to the joining together of a weak gradient magnetic field with the stronger main magnetic field, allowing the spatial localization of 2 tubes of water.
Zeugmatography
Introduced the use of gradients in the magnetic field.
Paul Lauterbur
Raymond Damadian receives his patent in ______.
1974
proposes using phase and frequency encoding and Fourier transform for acquisition of MR images.
Richard Ernst 1975
introduced 2D NMR using phase and frequency encoding, and the Fourier Transform.
Richard Ernst
nearly five hours after the start of the first MRI test, the first human scan was made as the first MRI prototype.
July 3, 1977
demonstrated imaging of the body using Ernst’s technique in 1980. A single image could be acquired in approximately five minutes by this technique
Edelstein and coworkers
FONAR Corporation receives FDA approval for its first MRI scanner.
1984
the first commercial MRI system.
Toshiba
publishes an article in Radiology, which describes diffusion weighted imaging (DWI)
Le Bihan in 1986
Real time MR imaging of the heart is developed___
1987
developed the first truly portable MRI technology and made MRI technology available in the office of the clinician
1999, MagneVu
a computer-based cross- sectional imaging
modality.
MRI
MRI was originally called
nuclear magnetic resonance (NMR).
creates images of structure through the interaction of magnetic fields and radio waves with tissue .
MRI
Small magnet created by the electron spin.
MAGNETIC DIPOLE
Accumulation of many dipoles.
Magnetic Domain
artificially produced by charging it in the field of a electromagnet.
Permanent Magnet
consist of wire wrapped around an iron core.
Electromagnet
Materials that are unaffected when brought into a magnetic
field
Diamagnet
Strongly attracted by a magnet.
Ferromagnetic
(most useful
magnets produced by ferromagnetic material)
Alnico – an alloy of aluminum, nickel and cobalt
Slightly attracted to a magnet and loosely influenced by an
external magnetic field
PARAMAGNETIC
CONTRAST AGENTS USED IN MRI
Paramagnetic
earth’s magnetic field at the equator
50 µT
earth’s magnetic field at the poles
100 µT
Typically coils of wire through which a magnetic field is induced
RESISTIVE MAGNETS
less than 0.3T due to its excessive power requirements.
Resistive Magnets
The most commonly used magnet.
* Alnico alloy that is used to make permanent magnets.
Permanent Magnet
only low fixed field-strengths (0.2– 0.3
T) can be achieved
Permanent Magnet
consist of a coil made of a niobium-titanium (Nb-Ti) alloy
SUPERCONDUCTING MAGNETS
high magnetic field strengths (0.5–3 T) with low power requirements.
SUPERCONDUCTING MAGNETS
Special cooling agents are use
to produce low temperature (4 K) is called .
liquid cryogens
electromagnetic coils are placed in an insulated
chamber called
dewar or cryostat
process of bringing the superconducting magnets
to the necessary temperature is
ramping
refers to a magnet’s sudden loss of
superconductivity with subsequent breakdown of the magnetic field
quenching
contain liquid Nitrogen
Outer Chamber of Dewar
contains liquid Helium
Inner Chamber Of Dewar
The precession in MRI is due
angular momentum.
portion of the magnetic field
extending away from the confines of the
magnet that cannot be used for imaging but
can affect nearby equipment or personnel
Fringe field
the rate at
which spins wobble when placed in a magnetic field. – DIRECTLY PROPORTIONAL TO THE STRENGHT
OF THE APPLIED MAGNETIC FIELD (B0
)
Larmor or precession frequency
The component of the net magnetization vector
parallel to the magnetic field is called
longitudinal magnetization.
The component perpendicular to the magnetic
field is called
transverse magnetization
