Chapter 1 Flashcards
the __ is the smallest constituent unit of ordinary matter which has the properties of a chemical element
atom
there are many popular depictions of what atoms look like, but few are accurate because __
the laws of quantum physics are not always intuitive
atoms consist of a __ and __
nucleus and electron cloud
the nucleus consists of __ (__ charge) and __ (__ charge)
protons (positive) and neutrons (no charge)
the electron cloud consists of __ (__ charge)
electrons (negative)
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 __
heavier; smaller in diameter
particles in the nucleus ( __ and __) are called __
protons and neutrons; nucleons
the __ consists of negatively charged particles which orbit the nucleus at velocities over 1000 km/s
electron cloud
electrons orbiting the nucleus are organized in __ according to the __
shells; laws of quantum physics
name the first five electron orbital shells
1s, 2s, 2px, 2py, 2pz
the mass number is the __ (i.e. the __)
total number of nucleons; the sum of protons and neutrons in the nucleus
the atomic number is the __
total number of protons in the nucleus
the __ indicates where a chemical element fits in the periodic table
atomic number
which is on top, the atomic number or the mass number?
the mass number
__ indicates to which isotope the atom belongs
the number of protons and neutrons in the nucleus
hydrogen has __ (#) isotopes: ___
3; protium, deuterium, tritium
which hydrogen isotope has 1 proton in the nucleus?
protium
which hydrogen isotope has 1 proton and 1 neutron in the nucleus?
deuterium
which hydrogen isotope has 1 proton and 2 neutrons in the nucleus?
tritium
nucleons are bound together by a short-range fundamental force called the __
strong interaction
if the number of neutrons is too different from the number of protons, the strong force __ which leads to __
cannot hold the nucleus together; radioactive decay
radioactive decay
a parent nucleus is split into at least 2 daughter nuclei
the __ provides information on all (known) isotopes for each element, according to their proton vs neutron number
Chart of Nuclides
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
isotopes; isotones; isobars
an unstable isotope is characterized by its __ i.e. __
half-life; the time it takes for some given amount of atoms of that isotope to decay to half their initial amount
half-lives vary from __ to __
fractions of a second; billions of years
isotopes are essential in medical imaging, particularly for modalities such as __
positron emission tomography (PET)
an ion is __ and can be __
an atom in which the number of electrons is not equal to the number of protons; positive or negative
a positive ion is called __
a cation
a negative ion is called __
an anion
the magnetic field is a __ field due to __
vector; moving electric charges (i.e. electric currents)
magnetic fields are measured in units of __
Tesla
to compute the magnetic field, we use the __
Biot-Savart Law
μ0 is the __
permeability of free space
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
solenoi
Ampere’s law: the integral of a magnetic field around any closed path is equal to the __ enclosed by that path, multiplied by the __
electric current; permeability of free space
the linear momentum p of a particle is a vector defined as __
the product of its mass m and its velocity v (p= mv)
mass is a __ quantity, meaning it only has __
scalar; a magnitude and sign
velocity is a __ quantity, meaning it has __, __, and __
vector; magnitude, sign, and direction
angular momentum L is the __
rotational analog of linear momentum (L = rp)
protons, neutrons, and electrons have a quantum-mechanical property called __, which is an intrinsic form of __
spin angular momentum (spin for short); quantized angular momentum
neutrons, protons, and electrons are __, i.e. they have a half-integer spin (1/2)
fermions
neutrons, protons, and electrons are fermions, i.e. they have a ___
half-integer spin (1/2)
what is the right hand rule?
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
what is the Zeeman effect?
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
if the particle has spin +1/2, it will align __
along the direction of B (parallel)
if the particle has spin -1/2, it will align __
against the direction of B (antiparallel)
spin, orbital, and total angular momentum
__
if Z (atomic number/# of protons) and N (# of neutrons) are equal, then the net spin angular momentum S is __
equal to zero because the spins of each nucleon type pair up and thus their individual effects cancel out
MR active nuclei and atoms where __
S does not equal 0
in MR imaging, the most important MR active nucleus is __
protium
why is protium the most important? (3)
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
an MR active nucleus has an intrinsic magnetic moment μ given by __
μ= γ S
γ is the __ and it __
gyromagnetic ratio; varies for different types of nuclei
the motion of an electrically charged particle induces a __ (μ) which is proportional to the __
magnetic moment; spin angular momentum (S)
in the relationship between magnetic moment and spin angular momentum, __ is the constant of proportionality
gyromagnetic ratio γ
the larger S is, the larger the __
magnetic moment
if a magnetic field B is applied in the presence of an MR active nucleus at body temperature, the nucleus acquires __
a magnetic moment which is aligned with B
low energy nuclei __
spin up, parallel to B
high energy nuclei __
spin down, antiparallel to B
the magnetic moment is quantized, i.e. __
it can only assume a discrete set of values
the magnetic moment can assume values ranging from __
-S(spin) to +S, in integer increments
if S = 5/2, the magnetic moment can be:
-5/2, -3/2, -1/2, +1/2, +3/2,+5/2
magnetic moment can assume a total of __ possible values
2s + 1
protium has a spin of __, and so the magnetic moment can be __
1/2; -1/2 or +1/2
spin-up state is a __ magnetic moment
positive
spin-down state is a __ magnetic moment
negative
spin __ state has a higher energy level
down
when a magnetic field is applied, some atoms align their magnetic moments __, others will be __
parallel to B0; antiparallel to B0
when a magnetic field B0 is applied, the energy E of the magnetic moment is given by:
E = - μ · B0 = - (γ S) · B0
for protium, the magnetic moment E when a magnetic field B is applied, is either __
E = γћB0/2 (spin-down) or E = -γћB0/2 (spin-up)
absolute zero:
0 K or -271.15 oC
at absolute zero, all atoms are __ because of the __
in their lowest energy state (all spin-up); third law of thermodynamics
as temperature increases, more and more atoms will __
acquire enough energy to switch from the spin-up state (antiparallel) to the spin-down state (parallel)
in practical circumstances (at room temp), the H atoms in the human body are near __, i.e. there is very little __
thermal equilibrium; flow of heat from one part of the body to another
at thermal equilibrium, __ of H nuclei will be in their up or down states. because of this, their magnetic moments will __
an unequal number; partially (but not fully) cancel each other out
when spin-up and spin-down magnetic moments do not exactly cancel each other out, there is a __
net magnetic moment
the number of spins __ to B exceeding the number of spins __ to B is called the __
parallel; antiparallel; spin excess
Δ𝑁 = 𝑁hω0/ 4𝜋𝑘𝑇
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)
an increase in B will cause an increase in E for atoms in their __ state
down
energy can be transferred to the nuclei in human tissue by __
increasing the strength of B0
as B increases so does the __ and the __ increases as well
strength of the net magnetic moment of each nucleus in the down state; net magnetization vector (M)
Bo is the __
static magnetic field
how many atoms are in one mol of a substance?
Avogadro’s number (6.022 x 10^23)
at thermal equilibrium, a sample of matter placed in a static Bo field acquires a ___
longitudinal magnetization Mo vector which is directed along the direction of Bo
spin density (Po)
the number of protons per unit volume of a sample
the measurable physical signal detected by MRI is due precisely to the existence of the __
longitudinal magnetization
longitudinal magnetization (Mo) =
blah, valid is MR active nucleus is H and T is in the room temp range
