Chapter 6 Magnetism

Question 1

True or false
All matter has magnetic properties.
Magnetism is a fundamental property of matter

Answer 1

True.
when someone says an item is nonmagnetic it most often means it is not ferromagnetic. all substances have some type of magnetic property

Question 2

What are the 3 main magnetic properties?

Answer 2

-diamagnetic
-paramagnetic
-ferromagnetic

Question 3

What are diamagnetic substances?

Answer 3

-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

Question 4

what is magnetic susceptibility?

Answer 4

refers to a substance or objects ability to become magnetized
(How susceptible is this to becoming magnetized)

Question 5

What is the magnetic susceptibility of diamagnetic substances?

Answer 5

(-1) susceptibility
-results in a repelling effect
-at very large field strengths small diamagnetic objects can levitate (15T or more)

Question 6

paramagnetic substances

Answer 6

-have unpaired electrons
-paramagnetic substances when placed in a magnetic field become magnetized
-gadolinium
-only magnetized while in the field, does not retain it

Question 7

What is the magnetic susceptibility of paramagnetic substances?

Answer 7

+1 susceptibility (or positive)

Question 8

what is gadolinium?

Answer 8

-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

Question 9

what is a chelate?
(how is gad made into a chelate?)

Answer 9

consists of a central metal ion (gadolinium) which is bound to a larger chemical compound called a ligand. together this is a gadolinium chelate

Question 10

when used as a contrast agent, paramagnetic properties of gadolinium result in what?

Answer 10

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

Question 11

Ferromagnetic substances

Answer 11

-highly magnetized when placed in an externally applied magnetic field
-retain their magnetization when removed from the field
-iron

Question 12

Nuclear Magnetism

Answer 12

-nuclear refers to the nucleus in atoms
-the magnetism of elements

Question 13

elements with an ____mass number are magnetically active.

Answer 13

odd
-they exhibit magnetic properties when placed in an externally applied magnetic field

Question 14

mass number is aka

Answer 14

atomic mass number

Question 15

examples of magnetically active nuclei are:

Answer 15

Carbon-13
Phosphorus-31
Hydrogen-1

Question 16

what is the most abundant magnetically active nuclei in the human body?

Answer 16

hydrogen
-nearly 100% abundant in the body
-water is 80%
this makes H ideal for MRI of the body

Question 17

the nucleus of a hydrogen atom consists of:

Answer 17

a single proton
-the proton has mass, a positive charge, and a property known as “spin”

Question 18

what is ‘spin?’

Answer 18

an intrinsic form of angular momentum carried by elemental particles
-the magnetic moment

Question 19

due to the odd mass number of hydrogen it also exhibits a small magnetic field known as the:

Answer 19

magnetic moment
-results in the hydrogen behaving like a tiny bar magnet

Question 20

when nuclei have an even number of protons and neutrons, the individual spins are paired, and the overall spin is:

Answer 20

zero

Question 21

if the sum of the number of neutrons and protons is an odd number, it will have:

Answer 21

half-integer spin (such as 1/2, 3/2, 5/2, etc)

Question 22

the spin integer value for hydrogen nuclei is:

Answer 22

1/2

Question 23

The term spin or spins is synonymous with:

Answer 23

proton or protons