Fundamentals Flashcards

1
Q

in the equation associated with LARMOR Equation, B(o)stand for

A

static magnetic field

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2
Q

in the equation associate with Larmor Equation, ω(o) stand for

A

frequency

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3
Q

in the equation associate with Larmor Equation, ϒ stand for

A

gyromagnetic ratio

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4
Q

a magnetic field strength of .05 T is equivalent to

A

5000 G

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5
Q

a condition whereby there are MORE spins in line with the magnetic field that opposed is knwn as

A

theralequilibrium

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6
Q

during thermal equalibrium there are

A

more spins in the low energy state

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7
Q

proton spins that are in line with the static magnetic field B(o) are referred to as all of the following

A

spin up

parallel

low energy spins

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8
Q

the microscopic magnetic field associated with the proton within the magnetic field is knwn as the

A

magnetic moment (µ)

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9
Q

during thermal equilibrium the vector taht represents the spn excess is known as the

A

net magnetization value (NMV)

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10
Q

the RF pulse is applied to acheive a condition known as

A

excitation

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11
Q

during excitation all of the following occur

A

low energy spins enter high energy state

spins begin to precess in phase

the NMV is transferred into the transverse plane

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12
Q

During relaxation all of the folloiwng occur

A

high energy spins return to a low energy state

spins begin to precess out of pahse or lose phase coherence

the NMV recovers longitudinally

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13
Q

T1 relaxation is also known as all of the following

A

T1 recovery

spin lattice

longitudinal recovery or relaxatoin

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14
Q

T2 relaxatoin is also known as

A

spin spin

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15
Q

T2 relaxatoin is also known as all of the following

A

T2 decay

spin spin

transverse relaxation

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16
Q

T1 relaxation time is defined as when

A

63% of the longitudinal magnetization has regrown

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17
Q

T2 relaxatoin time is defined as when

A

63% of the transverse magnetization has decayed

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18
Q

images acquired with a spin echo pulse sequence having a SHORT TR and TE valuse yield images known as

A

T1WI

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19
Q

images acquired with a spn echo pulse sequence having a LONG TR and TE valuses yield images known as

A

T2WI

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20
Q

images acquired with a spin echo pulse sequence having a LONG TR and SHORT TE valuse syield images known as

A

PDWI

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21
Q

spino density is another term for

A

proton density

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22
Q

spin density is determined by the

A

amount of excess spins in the low energy state at equilibrium

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23
Q

gradient echo (steady state) sequences acquired with short TR and flip angle combinations along with a moderately long TE yield images with

A

T2* contrast

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24
Q

T2 + T2’ equals

A

T2*

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25
the LOGICAL gradient that is used for slice selection for the acquisition of an axial slice is the
z gradient
26
the PHSYICAL gradient that is used for slice selection for the acquisition of an aial slice is the
z gradient
27
the LOGICAL gradient that is used for slice selection for the acquisition of a sagittal slice is the
z gradient
28
the PHYSICAL gradient that is used for slice selection for the acquisition of a sagittal slice is the
x gradient
29
the LOGICAL gradient that is used for phsae encoding for the acquisition of an axial slice of the abdomen is the
y gradient
30
the LOGICAL gradient that is used for phase encoding for the acquisition of an axial slice of the head is the
y gradient
31
the PHYSICAL gradient that is used for phase encoding for the acquisition of an axial slice of the abdomen is the
y gradient
32
the PHYSICAL gradient taht is used for phase encoding for the acquisition of an axial slice of the head is the
x gradient
33
the receiver bandwidth is related to the slope of the
frequency encoding gradient
34
following a 90 RF pulse the signal that is created is called
free induction decay
35
T2\* is a result of dephasing due to tissues T2 time and
susceptibility inhomogeneities chemical shift
36
the peak signal strength of a spin echo is less than the initial signal strength of the free induction decay because of
T2 relaxation
37
an example of a dipole is
hydrogen nucleus bar magnet earth
38
a vector has both direction and
magnatude
39
hydrogen nuclei have a magnetic moment because they possess a property called
spin
40
when placed in a large static magnetic field hygdrogen nuclei
align in either a parallel or anitparallel position
41
spins aligned in the antiparallel directino are in
high energy state
42
during thermal equilibrium the spin excesses of individual hydrogen nuclei add to form
a net magnetization vector NMV
43
the formula that describes the relationship between the static magnetic field and the precessional frequency bo the hydrogen protons is the
larmor equation
44
o calculate the precessional frequencey the strength of the static magnetic field is multiplied by a constan knows as the
gyromagnetic ratio
45
the condition reached with a few seconds of hydrogen being placed in a magnetic field is described as
thermal equilibrium
46
during thermal equilibrium the individual protons precess
out of phase
47
in order for energy to transfer between systems the two systems must be at the same
resonant frequency
48
assuming a TR sufficient for full recovery of longitudinal magnetization maximum signal is produced in the receiver coil when the net magnetization is tipped
90 deg
49
in relatoin to the static magnetic field the RF field is oriented
perpendicular
50
the RF energy used in MRI is classified as
electromagnetic radiation
51
immediatly on the application of the 90 pulse the precessing protons
begin to precess in phase
52
the MR signal is produced by magnetization
in the transverse plane
53
frequency can be defined by the
rate of phase change per unit time
54
gradient magnetic fields are used to
spatially encode the data
55
slice thickness is controlled by
slope of the gradient
56
the physcial graient along with the bore of the superconducting magnet is the
z gradient
57
to produce a sagittal slice the physical gradient used during the excitation pulse is the
x gradient
58
the gyromagnetic ratio for hydrogen is
42.6 MHz/T
59
in a 0.5 T imager the precessional frequency of hydrogen is approximately
21.3 MHz
60
the amount of RF energy necessary to produce a 45ͦͦ° flip angle is determined by the
coil being used ampl;itude and duratin of the RF pulse strength of the external magnetic field
61
the gradient that varies in amplitude wtih each TR is the
phase encoding gradient
62
the gradient that is on during the sampling of the echo is the
frequency encoding gradient
63
K-space is
the raw data from which an MR image is created
64
multiple coil elements combined with multiple receive channels is a
phased array coil