EXAM #11 — PHYSICS UNIT 04 Flashcards
define the following terms as they apply to nuclear magnetism in the MRI environment:
quantum mechanical description.
quantum mechanical description.
study of individual units of matter or energy (i.e. protons)
define the following terms as they apply to nuclear magnetism in the MRI environment:
classical mechanical description.
classical mechanical description.
study of bundles of matter or energy (i.e. net magnetization)
define the following terms as they apply to nuclear magnetism in the MRI environment:
nuclear magnetic moment.
nuclear magnetic moment.
sum total of the magnetic moments of the protons in a nucleus
define the following terms as they apply to nuclear magnetism in the MRI environment:
net magnetization.
net magnetization.
the sum total of the magnetic moments of all the protons in a sample of tissue
define the following terms as they apply to nuclear magnetism in the MRI environment:
precession.
precession.
the motion of a proton or net magnetic vector rotating about an external magnetic field
define the following terms as they apply to nuclear magnetism in the MRI environment:
Larmor frequency or resonant frequency, to include its unit of measurement.
Larmor frequency or resonant frequency, to include its unit of measurement.
the frequency at which the net magnetic vector precesses about the Z axis; or the frequency at which the net magnetic vector can absorb transmitted RF; measured in Hz
define the following terms as they apply to nuclear magnetism in the MRI environment:
resonance.
resonance.
the ability of the net magnetic vector to gain energy from an external source (RF)
define the following terms as they apply to nuclear magnetism in the MRI environment:
gyromagnetic ratio.
gyromagnetic ratio.
the precessional frequency of a specific nucleus at 1.0T
define the following terms as they apply to nuclear magnetism in the MRI environment:
rotating frame of reference.
rotating frame of reference.
the frame of reference that assumes that the observer is rotating with the motion of the net magnetization vector; simplifies the motion into 2 dimensions
define the following terms as they apply to nuclear magnetism in the MRI environment:
laboratory frame of reference.
laboratory frame of reference.
the frame of reference that assumes that the observer is stationary and all motion is being observed
define the following terms as they apply to nuclear magnetism in the MRI environment:
spin (or proton) density.
spin (or proton) density.
the relative number of spins or protons in a sample
identify the 3 subatomic particles that make up an atom, and their associated electrical charges.
proton (+), neutron (no charge), electron (-)
identify the 2 subatomic particles that make up an atomic nucleus.
proton, neutron
identify the subatomic particle that plays the biggest role in MRI signal formation.
proton
explain the relationship between the number of protons in an atomic nucleus and the magnetic moment of the nucleus.
only nuclei with an odd number of protons have a nuclear magnetic moment, the more protons in a nucleus the lower the magnetic moment (hydrogen has a high magnetic moment due to the single proton in the nucleus)
identify the element that is imaged in clinical MRI.
hydrogen
identify 2 reasons that hydrogen is imaged in clinical MRI.
large magnetic moment, abundant in the body
identify the energy states possible for a hydrogen atom in a static magnetic field.
high energy and low energy (anti- parallel and parallel)
explain the relationship between high and low energy states and parallel and antiparallel orientation to an external magnetic field.
high energy protons align anti-parallel, low energy protons align parallel
explain the orientations of atomic nuclei in the presence and absence of an external static magnetic field.
in the absence of an external field, nuclei are randomly oriented, in the presence of one they are aligned parallel or anti-parallel
explain the orientation and strength of net magnetization in the presence and absence of an external static magnetic field.
in the absence of an external field there is no net magnetization, in the presence of one there is net magnetization aligned with the external field
identify the gyromagnetic ratio of the hydrogen atom.
42.6MHz
identify the conventional direction of an external magnetic field on a vector diagram.
vertical, or aligned with the Z axis
identify the axis about which the net magnetization of a sample precesses at equilibrium.
Z axis
identify the letter used to denote net magnetization.
M
identify the notation for the net magnetization vector at equilibrium.
Mo
identify the notation for net magnetization as it precesses about the Z axis of a vector diagram.
Mz
identify the notation for net magnetization as it precesses in the XY plane of a vector diagram.
MXY
identify the relationship between the number of protons in a sample and the strength of the net magnetization of the sample.
as the number of protons increases, net magnetization increases
explain the relationship between the external magnetic field strength and net magnetization.
the higher the field strength the stronger the net magnetization
state the 2 properties that an RF pulse must have in order to create resonance.
RF pulse must be at the Larmor frequency and perpendicular to the external magnetic field (Bo)
