Chapter 1: Basic principles Flashcards
Classical Theory
Isaac Newton
-uses the concept of mass, spin, and angular moment on a large scale
Quantum theory
Plank, Einstein, Durac
- operates on a subatomic scale and refers to the energy of protons, neutrons, and electrons
hydrogen
the most abundant in the human body
- mostly found in the molecule of fat and water
atomic mass
protons + neutrons = nucleons
Heisenberg’s uncertainty principle
the position of an electron is not predictable because it depends on its energy
isotopes
atoms with odd mass number
ions
atoms that have excess of are deficient in electrons
ionization
process of knocking electrons from the atom which causes an electrical imbalance
MRI is based on
nuclear spin of hydrogen
motion present in the atom (3)
- electron spin on their own axis
- electrons orbit the nucleus
- nucleus spins on its own axis
nucleus doesn’t have spin if
it has an even number of atomic and mass numbers
net spin/ angular moment
spin directions are not equal and opposite
isotope of hydrogen
protium
MR active nuclei have
net electrical charge (electric field) and are spinning (motion)
magnetic field created by
charged moving particle
- this creates an electric field
hydrogen nuclei act like
magnets
- they have an north and south pole
B0
main static magnetic field
alignment
when hydrogen is placed in a strong magnetic field and they orient to it
3 fundamental ideas
- signal strength proportional hydrogen density
- Larmor frequency proportional to magnetic field strength
- spin needs time to realign with magnetic field (relaxation time)
parallel
magnetic moment aligned in same direction as B0 field
- spin up
anti-parallel
magnetic moment are in opposite direction of the B0
- spin down
NVM
net magnetic vector
- net magnetization of the patient
- aligned parallel to B0
- in longitudinal plan (z-axis)
Hydrogen nuclei energy states
low and high energy
Low energy
does not have enough energy to oppose B0 field
- spin up
High energy
has enough energy to oppose B0 field
- spin down
thermal equilibrium
patient temp is constant and doesn’t influence the thermal energy
precession
each hydrogen nuclei spins on its own axis
Larmor Frequency
precessional refquency equation
hydrogen at 1 Tesla
42.58
1 Tesla to Gauss
1T= 10,000 Gauss
Michael Faraday
law of electromagnetic induction
- refers to the connection between electric and magnetic fields and motion
- moving electric field produces a magnetic field
Boltzmann’s equation
patient’s thermal temp is an important factor that determines spin is in high or low energy population
phase
position of magnetic moment on their processional path at any time
unit of phase
radian
frequency
rate of change in the phase
