MEDRADSC 3DE3 Lecture Notes - Lecture 3: Atomic Number, Active Galactic Nucleus, Gyromagnetic Ratio
11 May 2018
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Three Magnetic fields
1. B0
a. Mai ageti field
b. “tati ag field
2. Gradients
3. RF
• Protons within the body interact with these fields
o Exposing H spins to mag fields and looking at how our bodies
are able to receive the energy and how quickly it dissipates
• Quantum physics – looks at the behavior of individual protons
• Classical physics – looks at changes in large groups of nuclei
Atomic Structure
• Molecule
o 2 or more atoms together
• Atom
o Has central nucleus, orbital electrons (cloud)
o Atomic number (only the sum of protons in nucleus) and mass
number (sum of protons and neutrons, typically even)
• H
o Typically found in water or fat (most common atom in the body)
• Nucleus, electrons
o The ue of eletos ad potos usually the sae, that’s why
atoms are stable
• Mass- nucleons- protons (positive charge)
o Nucleons: the particles inside
• Isotopes
o Same number of protons but slightly different number of neutrons
• Ions
o If electrons and protons are not in the same proportion
Three types of Motion within the atom
• Electrons spinning on own axis
• Electrons orbiting nucleus
• Nucleus spinning on its own axis
o We take advantage of this
o Even mass number (protons= neutrons), half spinning in one direction, the other half in
the other direction = no net spin
find more resources at oneclass.com
find more resources at oneclass.com
o Odd mass number, the spin directions will not be equal= net spin/angular momentum
→ this is what contributes to an MR active nuclei, spins will either align with B0 or
oppose it
MR Active Nuclei
• Align axis of rotation to B0
• Angular moment/spin
• Positively charge protons- electrical charge
• Faraday 1833- Law of electromagnetic Induction
• Three forces (motion and charge = magnetism)
• MR active nuclei, hydrogen is the most abundant in the body
Hydrogen
• MR active nucleus
• Single proton
• Atomic and mass number = 1
• Solitary proton – produces a relatively large magnetic moment
• Spins
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Isotopes: same number of protons but slightly different number of neutrons. If electrons and protons are not in the same proportion. This is what contributes to an mr active nuclei, spins will either align with b0 or oppose it. Mr active nuclei: align axis of rotation to b0, angular moment/spin, positively charge protons- electrical charge, faraday 1833- law of electromagnetic induction, three forces (motion and charge = magnetism) Length of vector: size of magnetic moment. B0: thermal energy level of nuclei (cid:894)(cid:272)a(cid:374)"t (cid:396)eally (cid:272)ha(cid:374)ge, (cid:396)elated to te(cid:373)p of patie(cid:374)t(cid:895, net magnetic vector (cid:862)(cid:395)ua(cid:374)tu(cid:373) theo(cid:396)y(cid:863, different between red and blue determines the net magnetic vector. Larmour equation: y (gyro magnetic ratio), a constant that expresses the relationship between angular momentum (net spin) and the magnetic moment of each mr active nucleus. It is a constant and is expressed as the precessional frequency of a specific mr active nucleus at 1t: unit is mhz/t, bo magnetic field strength static field.
