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MIDTERMS - 3RD YR TRANSES > MRI (2) > Flashcards

MRI (2) Flashcards

(57 cards)

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1
Q

discovered the __ in __in Budapest, Hungary. This was a fundamental discovery in physics

A

Nikola Tesla; Rotating Magnetic Field ;1882

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2
Q

In 1956, the __ was proclaimed by the International Electro-technical Commission-Committee of Action. All MRI machines are calibrated in __

A

“Tesla Unit”

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3
Q

THE STRENGTH OF A MAGNETIC FIELD IS MEASURED IN __

A

TESLA OR GAUSS UNITS.

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4
Q

The stronger the magnetic field, the ___ which can be elicited from the body’s atoms and therefore the higher the quality of MRI images.

A

stronger the amount of radio signals

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5
Q

1 Tesla = __Gauss

A

10,000

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6
Q

Low-Field MRI

A

Under .2 Tesla (2,000 Gauss)

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7
Q

Mid-Field MRI - __

A

.2 to 0.6 Tesla (2,000 Gauss to 6,000 Gauss)

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8
Q

High-Field MRI - __

A

1.0 to 1.5 Tesla (10,000 Gauss to 15,000 Gauss)

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9
Q

In 1937,__ 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.

A

Professor Isidor I. Rabi,

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10
Q

discovered that hydrogen signal in cancerous tissue is different from that of healthy tissue because tumors contain more water.

A

RAYMOND DAMADIAN

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11
Q

a chemist and an NMR pioneer at the State University of New York, Stony Brook, produced the first NMR image.

A

PAUL LAUTERBUR

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12
Q

one of the graduate students cobbled a wearable antenna coil to monitor the hydrogen broadcast detected by the coil.

A

MIKE GOLDSMITH

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13
Q

first mri exam performed on a human being.
Dr. Raymond Damadian, Dr. Larry Minkott & Dr. Michael Goldsmith.

A

JULY 3, 1977

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14
Q

ORIGINAL NAMED OF THE FIRST MRI MACHINE.

A

“INDOMITABLE”

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15
Q
  • the most visible and probably the most often discussed component of the MRI system
  • it provides the powerful static (constant strength ) magnetic field about which the nuclei precess.
A

MAGNET

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16
Q

TYPES OF MAGNETS

A

Permanent magnets, Temporary Magnets, Electro-magnets

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17
Q

emit a magnetic field without the need for any external source of magnetism or electrical power.

A

Permanent magnets

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18
Q

behave as magnets while attached to or close to something that emits a magnetic field, but lose this characteristic when the source of the magnetic field is removed.

A

Temporary magnets

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19
Q

require electricity in order to behave as a magnet.

A

Electro-magnets

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20
Q

Materials for Ferromagnetism

A

Iron, Nikel, Cobalt

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21
Q

Materials for Paramagnetism

A

Aluminum, Tungsten, Platinum, Manganese

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22
Q

Materials for Diagmagnetism

A

Copper, Silver, Mercury, Carbon

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23
Q
  • is responsible for the alignment of nuclei
    1. Solenoid electromagnets the fields is usually horizontal
    2. Permanent magnets the fields is generally vertical
  • it exerts an induction force on ferromagnetic and paramagnetic substances
Study These Flashcards
A

MAGNETIC FIELD

24
Q

__ is the sum of protons in the nucleus
__ is the sum of protons and neutrons in the nucleus
An__ is electrically stable, if the number of negatively charged electrons orbiting the nucleus equals the number of positively charged protons in the nucleus.

Study These Flashcards
A

Atomic number
Atomic mass number
atom

25
Three types of motion are present within an atom:
1. Electrons spinning on their own axis 2. Electrons orbiting the nucleus 3. The nucleus itself spinning about its own axis
26
In addition, hydrogen has a different precessional frequency at different field strengths. At 1.5 TESLA the precessional frequency of hydrogen is__ At 0.5 TESLA the precessional frequency of hydrogen is __
63.86 MH; 21.28 MHZ
27
THE GYROMAGNETIC RATIO OF HYDROGEN IS ___
42.51 MHZ/T
28
Electromagnetic radiation just lower in energy than infrared. RF used in MRI is commonly in the __
Radiofrequency; 10 – 100 MHZ
29
is the position of each magnetic moment on the precessional path Bo.
Phase Coherent
30
comparatively slowly gyration of the axis of a spinning body so as to trace out a cone ; caused by the application of a torque tending to change the direction of the rotation axis. - The second spin of magnetic moment around Bo
Precession
31
the speed of precession
Precessional (Larmor) Frequency
32
spin, lattice, or longitudinal relaxation time - the characteristics time constant for spins to tend to align themselves with the external magnetic fields
T1 Relaxation Time
33
- spin – spin, transversal relaxation time - spins begin to precess oit of phase with each other
T2 Relaxation Time
34
- If transverse magnetization of the spins is produced, a transient MR signal will result, which will decay with a characteristics time constant T2. - As the magnitude of transverse magnetization decreases, so does the magnitude of the voltage induced in the coil. - Loss of signal due to relaxation
Free Induction Decay (FID)
35
the precessional frequency of an element at 1.0 TESLA
Gyromagnetic ratio
36
- denotes the direction of the north/south axis of a magnet and the amplitude of the magnetic field
Magnetic moment
37
- ability of a substance to become magnetized.
Magnetic susceptibility
38
- a property of all matter that depends on the magnetic susceptibility of the atom
Magnetism
39
the magnetic vector produced as a result of the alignment of excess hydrogen nuclei with magnetic field.
Net Magnetization Vector (NMV)
40
- is a phenomenon whereby an object is exposed to an oscillating perturbation that has a frequency close to its own natural of oscillation
Resonance
41
ATOMS THAT ARE ELECTRICALLY UNSTABLE DUE TO DEFICIT, OR AN EXCESS NUMBER OF ELECTRONS, ARE CALLED __
IONS.
42
MRI is based on the spinning motion of a specific kind of nuclei present in biological tissues. These are called __
MR active nuclei
43
These are characterized by their tendency to align their axis of rotation to an applied magnetic field.
MR ACTIVE NUCLEI
44
- it is the vector sum of the individual magnetic moments of all the protons in the nucleus
TOTAL MAGNETIC MOMENT
45
Due to the laws of quantum mechanics only nuclei with an __ of protons have a total magnetic moment and can interact with an external magnetic field.
odd number
46
The hydrogen nucleus contains a single proton (atomic number 1). - It is used because it is very abundant in the human body. - Its solitary proton gives a large magnetic moment
HYDROGEN NUCLEUS
47
- Low thermal energy nuclei - Low energy to oppose the external magnetic field.
PARALLEL NUCLEI
48
- High thermal energy nuclei - High thermal energy, do posses enough energy to oppose the strength of external magnetic field
2. ANTI-PARALLEL NUCLEI
49
- The static external magnetic field is called B0 - The interaction of the NMV with B0 the basis of MRI - The unit of is tesla or gauss.
Magnetization Vector (NMV)
50
- are loops of wire or thin conductive sheets on a cylindrical shell lying just inside the bore of an MR scanner. When current is passed through these coils a secondary magnetic field is created.
Gradients 
51
- is the generator of the radiofrequency current which is delivered to the transmitting coil. This creates a signal which is used to excite protons in the imaging field. 
TRANSMITTER COIL
52
Radiofrequency coils can be both __ and __ of the radiofrequency signal or receivers alone. - A radiofrequency coil that performs both of these actions is called a __
transmitters and receivers; transmit receiver coil or a transceiver coil.
53
A coil, or antenna, positioned within the imaging volume and connected to the receiver circuitry that is used to detect or receive the MR signal from the patient as the disturbed spins relax back into their equilibrium distribution.
RECEIVER COIL
54
MRI computer can be divided into
central processing unit (CPU), consisting of instruction, interpretation and arithmetic unit plus fast access memory.
55
Computer controls the __ and __ necessary to acquire data, and process the data to produce __ or images.
RF pulses and gradient; spectra
56
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MIDTERMS - 3RD YR TRANSES (8 decks)

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