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530: Data Acquisition > Chapter 1 > Flashcards

Chapter 1 Flashcards

1
Q

the __ is the smallest constituent unit of ordinary matter which has the properties of a chemical element

A

atom

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2
Q

there are many popular depictions of what atoms look like, but few are accurate because __

A

the laws of quantum physics are not always intuitive

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3
Q

atoms consist of a __ and __

A

nucleus and electron cloud

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4
Q

the nucleus consists of __ (__ charge) and __ (__ charge)

A

protons (positive) and neutrons (no charge)

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5
Q

the electron cloud consists of __ (__ charge)

A

electrons (negative)

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6
Q

the nucleus lies at the center of an atom and it is over 1000 times __ than the electron cloud, though it is more than 1,000,000 times __

A

heavier; smaller in diameter

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7
Q

particles in the nucleus ( __ and __) are called __

A

protons and neutrons; nucleons

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8
Q

the __ consists of negatively charged particles which orbit the nucleus at velocities over 1000 km/s

A

electron cloud

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9
Q

electrons orbiting the nucleus are organized in __ according to the __

A

shells; laws of quantum physics

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10
Q

name the first five electron orbital shells

A

1s, 2s, 2px, 2py, 2pz

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11
Q

the mass number is the __ (i.e. the __)

A

total number of nucleons; the sum of protons and neutrons in the nucleus

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12
Q

the atomic number is the __

A

total number of protons in the nucleus

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13
Q

the __ indicates where a chemical element fits in the periodic table

A

atomic number

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14
Q

which is on top, the atomic number or the mass number?

A

the mass number

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15
Q

__ indicates to which isotope the atom belongs

A

the number of protons and neutrons in the nucleus

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16
Q

hydrogen has __ (#) isotopes: ___

A

3; protium, deuterium, tritium

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17
Q

which hydrogen isotope has 1 proton in the nucleus?

A

protium

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18
Q

which hydrogen isotope has 1 proton and 1 neutron in the nucleus?

A

deuterium

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19
Q

which hydrogen isotope has 1 proton and 2 neutrons in the nucleus?

A

tritium

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20
Q

nucleons are bound together by a short-range fundamental force called the __

A

strong interaction

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21
Q

if the number of neutrons is too different from the number of protons, the strong force __ which leads to __

A

cannot hold the nucleus together; radioactive decay

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22
Q

radioactive decay

A

a parent nucleus is split into at least 2 daughter nuclei

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23
Q

the __ provides information on all (known) isotopes for each element, according to their proton vs neutron number

A

Chart of Nuclides

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24
Q

in the Chart of Nuclides, __ are the rows of isotopes with the same proton number (of the same element), __ are the columns of isotopes with the same neutron number, and __ are the diagonals of isotopes with the same number of nucleons

A

isotopes; isotones; isobars

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25
Q

an unstable isotope is characterized by its __ i.e. __

A

half-life; the time it takes for some given amount of atoms of that isotope to decay to half their initial amount

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26
Q

half-lives vary from __ to __

A

fractions of a second; billions of years

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27
Q

isotopes are essential in medical imaging, particularly for modalities such as __

A

positron emission tomography (PET)

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28
Q

an ion is __ and can be __

A

an atom in which the number of electrons is not equal to the number of protons; positive or negative

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29
Q

a positive ion is called __

A

a cation

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30
Q

a negative ion is called __

A

an anion

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31
Q

the magnetic field is a __ field due to __

A

vector; moving electric charges (i.e. electric currents)

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32
Q

magnetic fields are measured in units of __

A

Tesla

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33
Q

to compute the magnetic field, we use the __

A

Biot-Savart Law

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34
Q

μ0 is the __

A

permeability of free space

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35
Q

a __ is a long wire wound in the form of a helix which allows a fairly uniform magnetic field to be generated in the space surrounded by the turns of the wire

A

solenoi

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36
Q

Ampere’s law: the integral of a magnetic field around any closed path is equal to the __ enclosed by that path, multiplied by the __

A

electric current; permeability of free space

37
Q

the linear momentum p of a particle is a vector defined as __

A

the product of its mass m and its velocity v (p= mv)

38
Q

mass is a __ quantity, meaning it only has __

A

scalar; a magnitude and sign

39
Q

velocity is a __ quantity, meaning it has __, __, and __

A

vector; magnitude, sign, and direction

40
Q

angular momentum L is the __

A

rotational analog of linear momentum (L = rp)

41
Q

protons, neutrons, and electrons have a quantum-mechanical property called __, which is an intrinsic form of __

A

spin angular momentum (spin for short); quantized angular momentum

42
Q

neutrons, protons, and electrons are __, i.e. they have a half-integer spin (1/2)

A

fermions

43
Q

neutrons, protons, and electrons are fermions, i.e. they have a ___

A

half-integer spin (1/2)

44
Q

what is the right hand rule?

A

the hint that if you put your right hand around L/B0, and extend your thumb in the direction of B0, your fingers will be curled in the direction of angular momentum

45
Q

what is the Zeeman effect?

A

when a fermion is placed is a magnetic field, the particle’s spin will align with the magnetic field in parallel or anti-parallel fashion

46
Q

if the particle has spin +1/2, it will align __

A

along the direction of B (parallel)

47
Q

if the particle has spin -1/2, it will align __

A

against the direction of B (antiparallel)

48
Q

spin, orbital, and total angular momentum

A

__

49
Q

if Z (atomic number/# of protons) and N (# of neutrons) are equal, then the net spin angular momentum S is __

A

equal to zero because the spins of each nucleon type pair up and thus their individual effects cancel out

50
Q

MR active nuclei and atoms where __

A

S does not equal 0

51
Q

in MR imaging, the most important MR active nucleus is __

A

protium

52
Q

why is protium the most important? (3)

A

water is a major component of biological tissues; protium is the most abundant isotope of hydrogen in nature; the magnetic moment of protium is large compared to other nuclei

53
Q

an MR active nucleus has an intrinsic magnetic moment μ given by __

A

μ= γ S

54
Q

γ is the __ and it __

A

gyromagnetic ratio; varies for different types of nuclei

55
Q

the motion of an electrically charged particle induces a __ (μ) which is proportional to the __

A

magnetic moment; spin angular momentum (S)

56
Q

in the relationship between magnetic moment and spin angular momentum, __ is the constant of proportionality

A

gyromagnetic ratio γ

57
Q

the larger S is, the larger the __

A

magnetic moment

58
Q

if a magnetic field B is applied in the presence of an MR active nucleus at body temperature, the nucleus acquires __

A

a magnetic moment which is aligned with B

59
Q

low energy nuclei __

A

spin up, parallel to B

60
Q

high energy nuclei __

A

spin down, antiparallel to B

61
Q

the magnetic moment is quantized, i.e. __

A

it can only assume a discrete set of values

62
Q

the magnetic moment can assume values ranging from __

A

-S(spin) to +S, in integer increments

63
Q

if S = 5/2, the magnetic moment can be:

A

-5/2, -3/2, -1/2, +1/2, +3/2,+5/2

64
Q

magnetic moment can assume a total of __ possible values

A

2s + 1

65
Q

protium has a spin of __, and so the magnetic moment can be __

A

1/2; -1/2 or +1/2

66
Q

spin-up state is a __ magnetic moment

A

positive

67
Q

spin-down state is a __ magnetic moment

A

negative

68
Q

spin __ state has a higher energy level

A

down

69
Q

when a magnetic field is applied, some atoms align their magnetic moments __, others will be __

A

parallel to B0; antiparallel to B0

70
Q

when a magnetic field B0 is applied, the energy E of the magnetic moment is given by:

A

E = - μ · B0 = - (γ S) · B0

71
Q

for protium, the magnetic moment E when a magnetic field B is applied, is either __

A

E = γћB0/2 (spin-down) or E = -γћB0/2 (spin-up)

72
Q

absolute zero:

A

0 K or -271.15 oC

73
Q

at absolute zero, all atoms are __ because of the __

A

in their lowest energy state (all spin-up); third law of thermodynamics

74
Q

as temperature increases, more and more atoms will __

A

acquire enough energy to switch from the spin-up state (antiparallel) to the spin-down state (parallel)

75
Q

in practical circumstances (at room temp), the H atoms in the human body are near __, i.e. there is very little __

A

thermal equilibrium; flow of heat from one part of the body to another

76
Q

at thermal equilibrium, __ of H nuclei will be in their up or down states. because of this, their magnetic moments will __

A

an unequal number; partially (but not fully) cancel each other out

77
Q

when spin-up and spin-down magnetic moments do not exactly cancel each other out, there is a __

A

net magnetic moment

78
Q

the number of spins __ to B exceeding the number of spins __ to B is called the __

A

parallel; antiparallel; spin excess

79
Q

Δ𝑁 = 𝑁hω0/ 4𝜋𝑘𝑇

A

spin excess; h is the Plank constant, k is the Boltzmann constant, w0 is the Larmor precession frequency, N is the number of atoms in the sample, and T is the absolute temp (in K)

80
Q

an increase in B will cause an increase in E for atoms in their __ state

A

down

81
Q

energy can be transferred to the nuclei in human tissue by __

A

increasing the strength of B0

82
Q

as B increases so does the __ and the __ increases as well

A

strength of the net magnetic moment of each nucleus in the down state; net magnetization vector (M)

83
Q

Bo is the __

A

static magnetic field

84
Q

how many atoms are in one mol of a substance?

A

Avogadro’s number (6.022 x 10^23)

85
Q

at thermal equilibrium, a sample of matter placed in a static Bo field acquires a ___

A

longitudinal magnetization Mo vector which is directed along the direction of Bo

86
Q

spin density (Po)

A

the number of protons per unit volume of a sample

87
Q

the measurable physical signal detected by MRI is due precisely to the existence of the __

A

longitudinal magnetization

88
Q

longitudinal magnetization (Mo) =

A

blah, valid is MR active nucleus is H and T is in the room temp range

530: Data Acquisition (13 decks)

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