Chapter 6 Magnetism Flashcards
True or false
All matter has magnetic properties.
Magnetism is a fundamental property of matter
True.
when someone says an item is nonmagnetic it most often means it is not ferromagnetic. all substances have some type of magnetic property
What are the 3 main magnetic properties?
-diamagnetic
-paramagnetic
-ferromagnetic
What are diamagnetic substances?
-have paired electrons in their orbital shell
-exhibit a slight negative or repelling effect when placed in an externally applied magnetic field
-the magnetic field is intensified or greater on the outside of the substance or object
-water, wood, plastics, gold, copper, mercury
-only magnetized while in the field, does not retain it
what is magnetic susceptibility?
refers to a substance or objects ability to become magnetized
(How susceptible is this to becoming magnetized)
What is the magnetic susceptibility of diamagnetic substances?
(-1) susceptibility
-results in a repelling effect
-at very large field strengths small diamagnetic objects can levitate (15T or more)
paramagnetic substances
-have unpaired electrons
-paramagnetic substances when placed in a magnetic field become magnetized
-gadolinium
-only magnetized while in the field, does not retain it
What is the magnetic susceptibility of paramagnetic substances?
+1 susceptibility (or positive)
what is gadolinium?
-the element on which most MR contrast agents are based
-have 7 unpaired electrons
-rare earth or heavy lanthanide metal
-highly toxic
-not excreted by the kidneys, it will go to and remain in the liver and bone marrow
-administered as a chelate to be safely used
what is a chelate?
(how is gad made into a chelate?)
consists of a central metal ion (gadolinium) which is bound to a larger chemical compound called a ligand. together this is a gadolinium chelate
when used as a contrast agent, paramagnetic properties of gadolinium result in what?
a shortening of both the T1 & T2 relaxation times of water-based hydrogen protons
-the shorter T1 relaxation times result in increased signal on t1 weighted images
Ferromagnetic substances
-highly magnetized when placed in an externally applied magnetic field
-retain their magnetization when removed from the field
-iron
Nuclear Magnetism
-nuclear refers to the nucleus in atoms
-the magnetism of elements
elements with an ____mass number are magnetically active.
odd
-they exhibit magnetic properties when placed in an externally applied magnetic field
mass number is aka
atomic mass number
examples of magnetically active nuclei are:
Carbon-13
Phosphorus-31
Hydrogen-1
what is the most abundant magnetically active nuclei in the human body?
hydrogen
-nearly 100% abundant in the body
-water is 80%
this makes H ideal for MRI of the body
the nucleus of a hydrogen atom consists of:
a single proton
-the proton has mass, a positive charge, and a property known as “spin”
what is ‘spin?’
an intrinsic form of angular momentum carried by elemental particles
-the magnetic moment
due to the odd mass number of hydrogen it also exhibits a small magnetic field known as the:
magnetic moment
-results in the hydrogen behaving like a tiny bar magnet
when nuclei have an even number of protons and neutrons, the individual spins are paired, and the overall spin is:
zero
if the sum of the number of neutrons and protons is an odd number, it will have:
half-integer spin (such as 1/2, 3/2, 5/2, etc)
the spin integer value for hydrogen nuclei is:
1/2
The term spin or spins is synonymous with:
proton or protons
