XrAY WEEK 3 Flashcards
ionization
removal of an e-
radiodensity is sometimes used to describe
radioqacity
ionizing radiation may either be ___ & _______
electromagnetic or particulate in nature
examples of ionizing particle radiation includes
alpha and beta particles
the two types of e-magnetic energy that has enough energy to ionize matter? and where do they originate from?
Gamma- originates from the nucleus X-rays - originates from the e- shells
radioactive atoms have unstable what?
nucleus
unstable nuclei of atoms may eject what two things?
particles and/or energy to attain more stable configuraiton
alpha particle is made up of
2 protons and 2 neutrons
beta particles are made up of
electron like particle much less mass than alpha and travels further than the alpha
half life is the time necessary for what?
time necessary for rate of atomic disintegrations to decrease by one-half
Photon
= smallest unit of e-magnetic radiation
smallest unit of elecrtomagnetic radiation
photon
photon travels at the speed of what
light
do photons have a charge?
does a photon have a mass?
no
photons have what 2 components
electric and magnetic fields *
Important characteristics of electromagnetic waves
Velocity (for our discussion of x-rays fixed, ie., always speed of light = c ) Frequency (nu or f ) Wavelength (lambda λ)
velocity formula
frequency * wavelength
there is an _____ relationship of frequency and wavelength due to a fixed ____
inverse , velocity
photon energy is ____ related to ___ velocity
1.directly 2.fixed
frequency relationship to the energy of a photon is
a direct relationship ~
as F increases = Photon energy increases
as frequency increases what happens to the energy
it increases
inverse square law
The intensity (amount of energy per unit area) of radiation changes inversely according to the square of the distance from the source
how to solve for the inverse square law
Express the change in distance as either a fraction or a multiple (eg, “on-third the distance” or “three times as far”) Take the INVERSE of the fraction or multiple (eg, inverse of 1/3 = 3 or inverse of 3 = 1/3) SQUARE it to find the change in intensity (eg, 2x2 = 4 or 1/3 x 1/3 = 1/9)
x-rays represent a range of _____ near the highest level of electromagnetic spectrum
frequencies
all x rays _____ have the same amount of frequency or wavelength meaning they do not have the same?
a. do not,
b. do,
a. DO NOT
2. Energy
X-rays behave more like particles than
“waves”
Electromagnetic radiation with wavelengths longer than that of the x-ray spectrum behave more
as waves
X-ray characteristics
Cannot be focused or reflected in the fashion of visible light Have the ability to penetrate matter Can cause some substances to fluoresce (emit visible light) Travel in in a straight line thru space Can cause ionization (ejection of electron from atom) Can expose photographic film Potentially harmful to living organisms- much more on this later Are more likely to interact with matter that has size similar to x-ray wavelength
Radiolucent =
material thru which x-rays pass more easily Analogous term to visible light concept of “translucent” material
Radiopaque =
material thru which x-rays do not pass easily Analogous term to visible light concept of “opaque” material
The radiopacity of objects is related to their physical _____?
density (more dense = more radiopaque)
The 5 are, in order of increasing radiopacity, (OR less radiolucent)
Air Fat Water Calcium (bone) Metal
organs and tissues are more like what density?
water
x-rays turn the film what color?
black
radioqaque will appear more what on xray?
white due to increase of density
if you have a decrease of radiopaque it will appear what? (decrease of density)
darker
beam quality
refers to
photon energy
beam quantity
refers to
number of photons
hard vs soft x-rays
“Hard” x-rays have higher energy (less wavelength and higher frequency) “Soft” x-rays have lower energy (greater wavelength and lower frequency)
X-ray originates from what?
electron cloud
X-ray photon energy is typically expressed in units called electron _________ or, because diagnostic x-rays are produced by using high voltage potentials, the unit _______
- volts (eV) 2. kiloelectron volts (keV) is used
x-rays, gamma rays (and higher frequency ultraviolet radiation) are the only______ forms of electromagnetic radiation
ionizing
AMP =
unit of electrical current Describes how many electrons are moving
Current =
flow of electrons
VOLT =
unit of electrical potential describes how much force are electrons moving with
3 basic factors of x-ray machine exposure settings are:
AMPERAGE, VOLTAGE and TIME
Coulomb © =
Coulomb is the fundamental unit of electrical charge
Ampere (A) =
unit of electrical current
A flow of electrons is called “current”. Measures the # of electrons flowing in a circuit Equal to one coulomb of charge flowing through a conductor each second- it is therefore a measure of the rate that electrical charge is being transferred.
AC is known as
alternating current : moving in direct current : electron motion is n one direction only
a backward and forward motion
DC is known as
direct current : electron motion is n one direction only
voltage ripple
term to describe
the fluctuation in electrical potential that occurs in alternating current
* not desirable for produciton of x-ray
alternating current has what kind of graph pattern (trig)
sinusoidal
sinusoidal and pattern shows a pattern with voltage and amperage levels falling to?
zero 3X during each cycle
DC may have a ripple voltage? T/F
T: More like a pulse
rectification
changing of an AC to a DC
Full wave rectification
inverts one half of a single phase current Electron flow again in one direction, but gap reduced
There is still a brief period during which voltage and current values fall to zero = large voltage ripple
3 phase current reduces voltage ripple by
superimposing 3 single phase waveforms, slightly out of time with one another.
3 phase current can be rectified to further minimize
voltage ripple
high frequency voltage
most current technology.
less of a voltage ripple much more efficient way to take x-ray
as wavelength increases what happens to the photon energy
it will decrease because they have an inverse relationship
1/2 rectification
eliminates 1/2 of single phase waveform ~ resulting in increase of gap and voltage variation
full wave rectification vs 1/2 wave rectification
full wave:
inverts 1/2 of single phase current
1/2 wave rectification: eliminates 1/2 of single phase wave form
