ch. 1&2 overview and electricity and magnetism

energy, wavelength, and phase

electromagnetic spectrum

magnetic resonance images made with radiofrequency

10-300 MHz

MRI originally called

nuclear magnetic resonance 

pt is stimulated so ___ is emitted from the body, the signal is then used to produce the image

electromagnetic radiation

considered the father of MRI

Felix Bloch

described __ with Bloch equations

nuclear magnetism

Bloch equations explain that because a nucleus spins on an axis, it has a

magnetic field

field is called 

magnetic moment

why MRI

no ionizing radiation

high contrast resolution

MRI spatial resolution depends on

tissue characteristics

MRI can obtain direct transverse, sagittal, coronal, and oblique plane images

multiplanar imaging

place cursor on lesion within a region of interest and retrieve NMR spectrum

spectroscopy

similar to CT, controls for post-processing, mechanical incrementation
for patient localization, move patient to isocenter

operating console

Graph of signal intensities created to identify the tissue and location within the field

fourier transformation

at isocenter, gradient is

0

deals with stationary electric charges

electrostatics

proton has one unit of

positive charge (stationary)

electron has one unit of

negative charge (free to move)

1 couolomb =

6.24 × 10¹⁸ electronic charges

When electrons are added to or removed from a material

electrified

Excess electrons move to neutral or e- deficient object

contact electrification

two objects touching causes transfer

friction electrification

Mass or energy transferred without actual contact between objects

induction electrification

a force field called the __ is associated with each charge

electric field (E)

lines of force begin on __ charges and end on __ charges

positive

negative

The magnitude of the electric field is the force on a unit charge

E= F/Q

E is

electric field intensity

F is

force on charge

Q is

electric charge

like charges __, unlike charges __

repel

attract

force can be quantified with 

coulomb’s law

coulomb’s law formula

F = k × q × Q/d²

d is

distance

k is

constant

free electrons tend to distribute themselves

evenly on surface of an object

required to push unlike charges together or to pull like charges apart

work

work must come from an __ and is deposited into __

energy source

energy sink

work equation

E= QV

V is

electric potential

the science of electric charge in motion

electrodynamics

electrodynamics involves

electric current or electricity

what kind of circuit is necessary for electric current?

closed

more __ makes electrons travel slowly

resistance

the number of electrons traveling is

ampere

1 ampere is equal to

1 couolomb per second (6.24 × 10¹⁸ electrons per second)

1 ampere difficult to measure because

there are so many electrons

we measure electric current by its

associated magnetic field

__ in lightning bolt to __ in electronic equipment

thousands of amperes

picoamperes

the current in your house can be up to about

30 A

a current of __ is usually fatal

100 mA at 110 volts

Electrons flow in one direction and then flow in the opposite direction (used in houses)

alternating current

Electrons flow in one direction only (used in car batteries)

direct current (DC)

in AC circuit, electrons start at

rest

AC circuit gradually speeds up, slow down and flow

opposite direction with increasing and decreasing speed

When electrons flow, they often bump into each other or are slowed down due to the size or shape of the conductor

impedance

3 types of impedance

capacitive

inductive

resistive

ohm’s law

V= IR

R= V/I

R is

resistance in ohm (Ω)

I is

electric current in ampere

conductors have what kind of resistance

low (e.g. copper, aluminum)

insulators have what kind of resistance

high (e.g. rubber, glass)

Resistance between that of conductor and insulator

semiconductor (e.g. silicon, computer chips)

resistance is 0

superconductor (e.g. MRI magnets)

superconductors must be

cooled to a very low temperature

Electric Power (P) formula

P = E/t OR P = I² × R OR V₂/R

energy and work measured in

joules (J)

power is measures in

watt (W)

light bulbs are usually between

60 W and 100 W

MRI magnets require more than

100 kW

fundamental property of matter

all matter is magnetic to some degree

easily magnetized

ferromagnetic (e.g iron, nickel, cobalt)

very weakly magnetized

paramagnetic (aluminum, platinum)

unaffected by a magnetic field

diamagnetism (copper, silver, mercury)

each magnet has two poles

diploes (north and south)

dividing a magnet creates

smaller magnets