Final Exam S1 Flashcards
Parsimony?
Simple explanations more likely to be true than complex ones
Reproducibility
Proofs should be able to be duplicated w/ same results
Falsifiability
Theories should be able to be logically and logistically proven false
Observation
Proofs should be able to be observed directly w/ the senses
Measurability
(results)
Results should be able to be measured and mathematically quantified
Scientific approach is _________
Self-correcting - it will always change
When were X-rays discovered?
November 8, 1895
Who discovered X-rays?
(registry question)
Wilhelm Conrad Roentgen
Who discovered fluoroscopy?
Thomas Edison
ALARA stands for?
As
Low
As
Reasonably
Achievable
Refers to occupational exposure
Largest source of radiation for average human?
Radon gas
(coming from earth)
Metric system is aka _______
Le Systeme International (SI)
Unit prefix for hundredths
centi = c
SI units:
Grays, Sieverts, Coulombs/kg2
British units:
RAD, REM, Roentgen
Unit prefix for millions
mega = M
Unit prefix for thousandths
milli = m
Unit prefix for millionths
micro = Mu
2 types of Mechanical Energy
Potential energy
Kinetic energy
Law of Conservation of Energy
Energy can’t be created/destroyed
Energy can only be transformed
Unit prefix for thousands
kilo = k
Potential Energy
Energy of position
Conduction heat
Direct contact
Kinetic Energy
Energy of motion
Convection heat
Mixing of hot & cold molecules
99% of X-ray tube interactions are ____ interactions
Heat
Radiation heat
Transfer
1 reason to use technique charts
Consistency
How to determine technique?
Body part
Measurement of body part
Proton
Positively charged particle located in nucleus
Neutron
No charge particle
located in nucleus
Electron
Negatively charged particle orbiting nucleus & creating orbital layers
Atomic shells
Letters: K - Q
Principle Quantum Numbers: 1 - 7
2n^2 rule
Octet rule
Nucleon
Protons & neutrons
Z number
Number of protons in (elements) nucleus
Number of electrons in stable atom
Alpha particle
2 protons & 2 neutrons
Changes atom’s elemental structure
20x more damaging than X-rays
(Due to the size)
2n^2 rule
Maximum number of electrons allowed in a shell when n = Principle Quantum Number
Octet rule
Outermost shell can never hold more than 8 electrons
Mixture
2+ substances not chemically bonded
aka Suspension
Atomic weight
Slightly higher than number of nucleons
Ionic bond
Postive & negative ions attracted to each other electrically
Super strong bond
Covalent bond
Bonding of 2 atoms w/odd number of electrons
2 atoms share “extra” electrons in figure 8 pattern
Much weaker than ionic bond
Molecule
2+ atoms chemically bonded together
Radioactive state
Nucleus is unstable & spends too much energy holding itself together
Ground state
Most stable configuration of nucleons
Correct number of neutrons to stabilize atom
Beta particle
Breakdown of neutron into positive neutron (now a proton) & high-speed negative electron
5x more damaging than X-rays
Isotope
Atom w/ unusual number of neutrons
Not necessarily radioactive
Gamma rays
Energy release from unstable nucleus w/o change to atomic structure
Naturally occurring X-rays
Ionization
Gain/loss of electron by atom
Creates net electrical charge
(due to addition/subtraction of electron)
Ion pair
Ejected electron & its atom
2 ways electron can be removed creating an ion?
Incident electron
Incident X-ray
How is radiation formed from inner and outer shell electrons?
Inner shell electron is removed from orbit & replaced by outer shell electron
Binding energy
Amount of energy used to hold orbital electron in place
Amount of energy needed to knock electron out of orbit
keV requirement for electron removal
keV equal to or greater than its binding energy
Wavelength
Distance between two like points on wave
Measured in Angstroms
Angstrom = 10^ -10 m
Outer shell electron gives off its energy in the form of _____
X-ray
Tungsten: M shell
Quantum number & Binding energy?
Quantum #3
Binding energy 3 kV
Tungsten Z number
74
Test 2 start:
Velocity
How fast energy of wave moves from one point to another
Strength of X-ray is equal to _____
Difference between the 2 binding energies
Tungsten symbol
W (Wolfram)
Amplitude
Maximum displacement of media from its equilibrium
Strength of wave, not its energy
Tungsten: K shell
Quantum number & Binding energy?
Quantum #1
Binding energy 69 kV
Frequency
Number of cycles passing a fixed point in a second
Measured in Hertz
Tungsten: L shell
Quantum number & Binding energy?
Quantum #2
Binding energy 12 kV
Electromagnetic wave formula
c = frequency x wavelength
c = speed of light
All electromagnetic waves travel at speed of light (in vacuum)
If frequency increases, wavelength decreases
Energy is directly proportional to frequency
Velocity equals ___ x ___
frequency
wavelength
Frequency & wavelength have ___ proportional relationship
inverse
Energy is directly proportional to ___
frequency
X-rays have ___ nature
dual
light photons and physical properties
Energy is ___ proportional to frequency
directly
Resonance
electromagnetic radiation interacting with substances with similar natural frequency
High energies behave like ___
particles
Absorption: Light vs. X-ray
Light: yes
X-ray: yes
Low energy X-rays
X-rays that interact w/ radiopaque objects
Reflection: Light vs. X-ray
Light: yes
X-ray: no
Radiolucent
X-rays can pass easily thru
Transmission: Light vs. X-ray
Light: yes
X-ray: yes
High energy X-rays
X-rays that interact w/ radiolucent objects
Refraction: Light vs. X-ray
Light: yes
X-ray: no
Dispersion: Light vs. X-ray
Light: yes
X-ray: no
Attenuation
Partial absorption of light or X-rays
Radiopaque
Very few X-rays pass thru
Magnetic moment
magnetic field for SINGLE electron or proton
Electromagnetism
All moving electric charges develop magnetic fields
Magnetic dipole
magnetic field around entire ATOM
(Small)
Magnetic domain
Group of magnetic dipoles pointed in same direction
GROUP of ATOMS w/ magnetic dipoles pointed in same direction
Ferromagnetic
Iron/nickel materials w/ magnetic domains easily lined up in same direction
Paramagnetic
Materials slightly attracted to magnetic fields
Al, O, Au, Cu
Diamagnetic
Materials slightly repel magnetic field
Glass, water
Retentivity
Ability of magnet to hold on to its magnetism over time
Non-magnetic
Materials unaffected by magnetic field
Wood, rubber
Strength of attraction/repulsion of poles follows the ___ law
Inverse square law
Magnetic fields are strongest near the ___
poles
Magnetic field - unit of measurement
Gauss (G) - roughly strength of earth’s magnetic field at the poles
Laws of Electrostatics
- Like charges repel, opposite charges attract
- Solid objects - only electrons move
- Solid objects - free electrons only exist on surface
- Solid objects - free electrons concentrate near point of greatest curvature
1 Tesla (T) equals ___ gauss
10,000
Electrostatics - unit of measurement
Coulomb
Static electricity is generally caused by electrification by ___
friction
Typical strength of MRI machine
2 Teslas (T)
Electrification
electrons move from one object to another
electrons in both objects is unequal
To minimize static, humidity should be above ___
40%
Electrification - Induction
charge is induced in another object w/o touching it
Electrification - Contact
potential difference exists between 2 objects touching each other
Electromotive force - unit of measurement
Volt
Electromotive Force (EMF)
Force created by any electric potential difference
Electrodynamics - Semiconductors
Electrical current flow in certain conditions
Electrodynamics - Conductors
Electrical current flow in most conditions
Current flow & electron flow are in ___ directions
opposite
Electrodynamics - Current
Flow of loosely-bound outer shell electrons
Electrodynamics - Insulators
No electrical current flow
Current - unit of measurement
Ampere / Amp
1 Coulomb per second
1 Coulomb per second is equal to ___
1 ampere
Ohm’s Law:
Formula
V = I x R
Voltage = Current x Resistance
Parallel circuit
Each component is connected to power source independently
Failure of one component only breaks circuit to that component, not the others
Resistance affected by:
Length, Diameter, Material of conductor
Series circuit
Each component of circuit is connected to each other
Failure of one component breaks the circuit
Electrical power
RATE at which electrical power is used
Resistance
Force preventing electrons from moving thru circuit
Electrical power - unit of measurement
Watt (W)
At frequency of 60 Hertz, each cycle lasts for ___
1/60th second
How many hertz in a second?
60
Alternating Current
Oscillation of current back & forth
How many pulses in a hertz?
2
3 ways to generate alternating current
1.Move conductor back & forth thru magnetic field - most common
2. Move magnetic field back & forth near conductor
3. Alternate the strength of magnetic field
Step-down transformer
Voltage goes down
Amperage goes up
How many pulses in a second?
120
Transformer
Use induction to transform voltage & amperage
Step-up transformer
voltage & amperage
Voltage goes up
Amperage goes down
True/False
Induction only works with Alternating Current
True
Autotransformer
Uses concept of self-induction to slightly change voltage in a circuit
What is the Typical incoming line voltage to the high voltage circuit?
220 volts
Autotransformer:
makes adjustments to voltage before it is stepped-up
on low-voltage side of the high voltage circuit for safety
What is part B in the x-ray machine?
Autotransformer
What is part A in the X-ray machine?
Main power switch
&
circuit breaker
3 ways the exposure switch and exposure time initiates/terminates
manual timer
mAs timer
Automatic exposure control (AEC)
What is part C in the x-ray machine?
Exposure switch
&
exposure timer
What is part D in the x-ray machine?
kVp Meter
(parallel circuit)
What is part F in the x-ray machine?
mA meter
(series circuit)
What is part E in the Xray machine?
Step-up transformer
turn ratio 500:1 to 1000:1
What is part H in the x-ray machine?
x-ray tube
thermionic emission- cathode (-)
x-ray production- anode (+)
Autotransformer (step?):
B
adjusts voltage before stepping up
What is part G in the x-ray machine?
Rectification bridge
(changes alternate to direct current)
What is part I in the x-ray machine?
Rotor switch
anode spin at 3400 RPM
heats up the filament
boils off electrons from filament due to high amps and high resistance
Main power switch and circuit breaker (step?):
A
Typical incoming line voltage is 220V
What is part J in the Xray machine?
mA selection
(resistors)
What is part K in the x-ray machine?
Step Down Transformer
ratio 1:44
up to 5 amps
Exposure switch and time (step?):
C
initiates exposure and terminates 1 of 3 ways:
Manual timer
mAs Timer
Automatic exposure control (AEC)
Step-up transformer (step?):
E
turns ratio 500:1- 1000:1
Kvp Meter (step?):
D
measures the Kvp
(parallel)
Rectification bridge (step?):
G
Diode changes alternate to direct current
electrons approach “n” side,
electrons are repelled towards bridge
p is positive side that repels holes toward the bridge
mA meter (step?):
F
Measures the amount of mA
(series)
rotor switch (step?):
I
spins anode 3400 rpm
heats up filament in the x-ray tube
thermionic emission due to high amperage and high resistance
x-ray tube (step?):
H
thermionic emission (cathode)
x-ray production (anode)
mA selection (step?):
J
Resistors
more resistors less amperage (vice versa)
Step down transformer (step?):
mA increased by:
K
ratio of 1:44
mA is increased by a factor of 44, up to 5 AMPS
Ch 9: xray tube
Cathode:
negative side of the x-ray tube
Thermionic emission
Half wave/self-rectified circuits
60 pulses a second
100% voltage ripple
30% average Kvp
Thermionic emission:
“BOILING OFF” electrons from filament due to high amperage and high resistance
Filaments are made up of:
thorium-impregnated tungsten
thorium z=90 helps with heat tolerance
single-phase/ full wave rectified
120 pulses a second
100% voltage ripple
30% average Kvp
3 phase/ 6-pulse generators
360 pulses per second
14% voltage ripple
91% average Kvp
3-phase/ 12-pulse generators
720 pulses per second
4% voltage ripple
97% average Kvp
high frequency generators
greater than 500 pulses
per second 500<
1% voltage ripple
100% average kvp
hz is altered from 60 to 500-25,000 HZ
Ch 9: xray tube
How many filaments in x-ray tube?
2 filaments
small= 1 cm
large: 1.5-2 cm
What does focal spot do?
Small?
Large?
smaller focal spot creates sharper images
large focal spot better for high heat x-rays (L-spine)
what is heat units for?
(What does it measure)
to measure how much heat the anode can withstand
(a unit of measurement for anode heat capacity)
Thermionic emission occurs in the:
What is thermionic emission?
Cathode
“boils off” electrons from the filament due to high current flow and high resistance
Focusing cup:
What is its charge?
Negative charge
prevents electrons from rushing away by surrounding the filament (negative focusing cup narrows the electrons due to the law of attraction)
focal spot (in anode) is _% of filament?
5%
(0.5mm-1mm)
Focal spot for hands/feet x-rays:
Small focal spot
1cm
What is space charge?
electron cloud forms around the filament when the rotor button is pushed
mAs directly controls the number:
of x-rays that exit the tube
Doubling mAs will:
double the amount of x-rays created
Target:
A part of what?
Made of what?
area of the anode disk that is struck by the electrons
made of tungsten and rhenium z=75
focal spot for lateral lumbar:
large focal spot
1.5cm to 2cm
Anode:
positive side of the x-rays tube
Xray production
What is struck by electrons in the x-ray tube?
the target in the anode (anode disk)
very durable to high amounts of heat
Rotor:
A part of what?
Anode
Connects the shaft and spins when influenced by the stator (induction)
What is arcing?
vaporized tungsten coats the inside of the tube
type of short circuit:
1. cracks the glass
2. eliminates vacuum
3. burns out the filament
Main cause of x-ray tube failure?
arcing
What is a way we can protect the x-ray tube?
(3)
- warm up procedures to prevent thermal shock (hot water on cold glass=crack)
- avoid excessive rotoring
- calculate the heat units to prevent overheating of the anode
What is the anode cooling chart purpose?
how long will it take for the anode to cool before making another exposure
What is the purpose for a tube rating chart?
to ensure that a technique will not exceed the heat capacity of an x-ray tube
HU (heat units) formula:
1.4 (constant/ don’t forget)
x
kVp
x
mA
x
s (seconds)
heat interactions:
99.5% of interactions at 60 Kv
99% of interactions at 100 kv
bremsstrahlung is responsible for the:
vast majority of x-rays
stream of electrons:
How fast?
using the voltages in x-ray electrons can accelerate at 1/2 the speed of light in just one inch
Bremsstrahlung:
“braking radiation”
interactions with the nucleus
Characteristic:
projectile electron from CATHODE interacts with INNER shell electron
it can be ejected
In Bremsstrahlung what is the average kv exiting?
(The avg kv after filtration is 1/3 of kvp setting)
the average KV exiting the x-ray tube after filtration is about 1/3 of the kVp setting
Any _____ can fill the vacancy in an inner shell electron, including ____ _______ outside the atom in characteristic
Electrons
Free electrons
Characteristic cascade:
Inner shell electrons are replaced in sequence (k by L,L by M, M by N,N by O).
MULTIPLE x-rays are created
What are the steps of characteristic?
- electron interacts with inner shell electron
- outer shell electron will drop down to fill the vacancy (L to K)
- The strength of the x-ray is equal to the difference between the two shell electrons
Filtration removes what kind of x-rays?
adding more filtration will:
Filtration removes weak x-rays
&
adding more filtration will remove even more weak ones
Increasing the average kvp
The result of characteristic cascade is x-rays at _____ _________
Specific energies
K shell- 57, 66, 68, 69 KV
L shell- 9,11,12 KV
(T/F)
when the Bremsstrahlung spectrum and characteristic spectrum are combined we have a complete graph of all the x-rays leaving the x-ray tube
True
What are factors that affect the x-ray emission spectrum?
- Target material (mammography)
- Milliampere-seconds (mAs)
- added filtration
- Kilovoltage-peak (kVp)
- generator type
(3 are of these are most common/ I think 2,3,4)
Increasing the kVp will move:
the x-ray emission spectrum to the right due to the increase energy from x-rays
When we filtrate more x-rays what happens to the average KV?
What is this known as?
the average KV will go up
this is known as “hardening” the x-ray beam
How do generator type play a role in x-ray emission spectrum?
mostimportantly the average kvp
Changes the pulses, voltage
ripple, average kvp
(high frequency, single phase, etc)
How does target material play a role in the x-ray emission spectrum?
(won’t be tested much on)
(Certain material will lower the average kvp)
like in mammography the material of the target will affect the average KV
(ex: in mammography avg is 17 KV)
Average KV after exiting the x-ray tube after:
filtration is about 1/3 of the kVp setting
therionic emission
a “boiling off” of electrons from the filament due to high current flow and high resistance
Hardening the x-ray beam:
adding more filtration for weak x-rays
thus increasing the average kVp
At the bridge current:
can flow
(T/F)
free electrons outside of the atom can fill the vacancy of the inner shell?
True
ANY electron
