Compre reviewer Flashcards by Cish Benedicto

a continuously changing flow of electrons that alternates its polarity at a periodic rate.

AC ( alternating current)

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the total number of independent data samples in the frequency (f) and phase (f) directions.

ACQUISITION MATRIX

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the process of measuring and storing image data.

Acquisition

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the period of time required to collect the image data. This time does not include the time necessary to reconstruct the image.

ACQUISITION TIME

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large network of interconnecting blood vessels at the base of the brain that when visualized resembles a circle.

CIRCLE OF WILLIS

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the act of maintaining a constant phase relationship between oscillating waves or rotating objects.

COHERENCE

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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

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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

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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

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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

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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)

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This was a fundamental discovery in physics.

Rotating Magnetic field

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Who discovered rotating magnetic field

Nikola Tesla

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what year tesla discovered rotating magnetic field

1882

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best known for many revolutionary contributions in the field of electricity and magnetism in the late 19th and early 20th centuries.

Nikola Tesla

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Recommended limit for constant human exposure

2mG

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The CGS unit for magnetic induction was named gauss in his honour

Carl Friedrich Gauss

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centimeter gram second system of units

CGS

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best known for initiating the investigation of Fourier series and their application to problems of heat flow.

Jean Baptiste Joseph Fourier

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s a mathematical procedure to separate out the frequency components of a signal from its amplitudes as a function of time

Fourier Transform

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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

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what year he proposed a quantum spin number for electrons

1924

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proposed a quantum spin number for electrons

Wolfgang Ernst Pauli

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proposed the Pauli exclusion principle, for which he received the Nobel Prize for Physics in 1945.

Wolfgang Ernst Pauli

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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

Compre reviewer Flashcards

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