Physics Ch. 2-7 Flashcards
Define matter
anything that occupies space and has shape or form
what are the three basic forms of matter?
- solid
- liquid
- gas
define mass
- quantity if matter that makes up any physical object
- weight
what is an example of mass
a 20lb bucket of water may freeze into a 20lb bucket of ice or it may evaporate, resulting in 20lb of water vapor. The form changes, but the mass remains the same.
define the Law of Conservation
- Matter can be neither created nor destroyed, but it can change form.
- Energy can be neither created nor destroyed, but it can change form.
define atom
basic building block of matter
what are the three fundamental components/particles of an atom?
- protons
- neutrons
- electrons
what two fundamental particles make up the nucleus?
protons and neutrons
where are electrons located in an atom?
they encircle around the nucleus in orbits called shells
what is the charge of protons?
positive
what is the charge of neutrons?
no charge
what is the charge of electrons?
negative
atoms can be ____ or _____
neutral or ionized
define a neutral atom
- normal/neutral state
- the atom has an equal number of protons and electrons
- electric charges are equal
- the atom has no charge
define ionized
contain a lesser or greater amount of electrons
how many shells are in an atom?
7
what are the names of the shells?
1 - k
2 - l
3 - m
4 - n
5 - o
6 - p
7 - q
what is the maximum number of electrons a K shell can have?
2
what is the maximum number of electrons an L shell can have?
8
what is the maximum number of electrons an M shell can have?
18
what is the maximum number of electrons an N shell can have?
32
what is the maximum numbers of electrons an O shell can have?
50
what is the maximum numbers of electrons a P shell can have?
72
what is the maximum numbers of electrons a Q shell can have?
98
which shell is the most important in radiology?
k-shell
define anion
when the atom gains an electron, changing the neutral charge into a negative charge
define cation
when the atom loses an electron, changing the neutral charge into a positive charge
define binding energy
a strong nuclear force that holds the nucleus and electrons together
define element
a substance made up of only 1 type of atom
what are some examples of elements?
calcium (Ca)
iodine (I)
lead (Pb)
define atomic number
number that represents the number of protons in a nucleus
why is a lead bullet easier to see in an x-ray rather than a calcium stone?
lead has an atomic number of 82, making it have a higher mass, and more density compared to calcium, which has an atomic number of 20
define mass number
combined total of protons and neutrons in the nucleus
how do you find the amount of neutrons in an element?
subtract the atomic number by the mass number
define molecules
when two or more atoms are combined
define chemical compound
a substance that consists of one type of molecule
ex.) water (H2O)
define mixtures
substances that contain more than one type of molecule
define energy
the ability to do work
which shell has the greatest binding energy? Why?
k shell because it is the closet to the nucleus
define chemical compounds
combination of elements bonded together
define potential energy
energy at rest
- “stored” energy
define kinetic energy
energy in motion
what are the classifications of energy?
- mechanical
- chemical
- thermal
- nuclear
- electric
- electromagnetic
define mechanical evergy
can be classified as kinetic or potential energy
define chemical energy
energy released through chemical changes in atoms or molecules
what is an example of chemical energy?
batteries, gasoline
define thermal energy
commonly known as heat, and is the result of atomic motion
whats an example of thermal energy?
when heated, electrons move rapidly. when cooled, electrons constrict
define nuclear energy
energy released by radionuclides
- energy used to produce electricity in a nuclear power plant
define electric energy
the ability of electric charges to do work
what are examples of electric energy?
- run computers
- make toast
- battery
- unused wall socket
- turning on a flashlight
define electromagnetic energy
has both electric and magnetic properties, changing the field through which they pass both electrically and magnetically
- includes light, x-rays, radio waves, and microwaves
define sine wave
a repeating wave/pattern
- also known as sinusoidal form
electromagnetic energy occurs in the form of a -
sine wave
define amplitude
- height of the wave
- distance between the trough and the crest of a sine wave
define wavelength
the distance from one crest to another
define frequency
the number of times per second that a crest passes a given point
what is the relationship between wavelength and frequency?
inverse relationship
- the higher the frequency, the shorter the wavelength
- the lower the frequency, the longer the wavelength
how can one find the velocity of a sine wave?
velocity = wavelength x frequency
what is the velocity/speed of electromagnetic waves?
186,000 miles/sec
when the x-ray has a higher energy, that means they have higher
penetration
what is the relationship between energy (kVp) and frequency?
direct
- when energy increases, frequency increases
what is the relationship between energy (kVp) and wavelength?
inverse
- when energy increases, wavelength decreases
all electromagnetic radiation has the _____ velocity
same
define ionizing radiation
- sufficient energy to remove an electron from its orbit
- wavelength of 1nm or less
- x-rays are one form of ionizing radiation
define photon
- smallest possible unit of electromagnetic energy
- tiny bundle of energy
list characteristics of x-rays
- travel in straight lines at a speed of 186,000 miles/sec
- have no mass
- highly penetrating and invisible
- are electrically neutral
- produced over a wide range of energies and wavelengths
- travel in straight lines at the speed of light
- can ionize matter
- produce biological changes in tissues
- produce secondary and scatter radiation
- cannot be detected by human senses
why are x-rays unique?
they have very high frequency and short wavelengths
are x-rays naturally produced or man made?
man made
electricity is used to -
produce x-rays
define electric current
- number of negative electrons flowing toward a positive charge
- circuit is the path over which electrons move
- measurement unit = ampere (A)
define circuit
- path over which electrons move
- continuous path
define potential difference
difference in electric charge between two points in the circuit
how is current produced?
when negatively charged electrons flow toward a positive charge
what are three electric factors that are part of an electric circuit?
- resistance
- current
- potential difference
define resistance
- any property of the circuit that opposes or hinders the flow of current
- amount depends on conductor material, length, diameter, and temperature
define current
the quantity of electrons flowing in a circuit
define ampere
unit used to measure the rate, or volume, or current flow in the circuit
- abbreviated A
define potential difference
the force or speed of the electron flow in the current
- measurement unit = volt (V)
define volt
the unit used to measure potential difference
- abbreviated V
what are the units of measurements for current?
- Ampere = A
- milliampere = mA
what are the units of measurements for kilovoltage?
- Volt = V
- kilovolt peak = kVp
define electric circuit
continuous path for the flow of electric charges from the power source through one or more electric devices and back to the source
what is the symbol for an anmeter?
a circle with the letter A inside
what is the function of the anmeter?
measures electric current
what is the symbol for voltmeter?
a circle with the letter V inside
what is the function of the voltmeter
measures electric potential
what is the symbol for a transformer?
coils
what is the function of a transformer?
increases or decreases voltage by fixed amount (alternating current only)
what is the symbol of a diode?
a line with an arrow
what is the function of a diode?
allows electrons to flow in only one direction
define alternating current (A-C)
-current flow changes or alternates directions at a rate of 60 cycles per second or 60 Hz in the U.S and Canada
- electric current is constantly changing
- current flow increases, peaks, and declines
what is the unit of electromagnetic frequency?
Hertz (Hz)
define rectification
- changing AC to DC
- AC is converted to flow in one direction only
does x-ray production rely on AC or DC?
DC
define direct current (D-C)
current flows at a constant rate in one direction from the positive pole (anode) to the negative pole (cathode)
using volts, how is a household circuit different from an x-ray circuit?
household: electric current is 120 V
x-ray circuit: electric current is 40,000-125,000 V
define electromagnetic induction
- a conductor is placed in a magnetic field and there is movement between the lines of magnetic force and the conductor, electric current will flow in the conductor
- moving a conductor within a magnetic field will produce AC
- moving a magnetic field across a conductor also produces AC
what is the primary purpose of a transformer?
change voltage by means of electromagnetic induction
- the primary and secondary coils will have different voltages
define step-up transformer
when there are more windings in the secondary coil than the primary coil
- voltage is higher on the secondary side
- kilovoltage increases, amperage decreases
define step-down transformer
when there are more windings in the primary coil than the secondary coil
- voltage is higher on the primary side
- kilovoltage decreases, amperage increases
what is the relationship between kilovoltage and amperage?
- inverse relationship
- shown in step up and step down transformers
- when kilovoltage increases, amperage decreases
what are the requirements to produce x-rays?
- vacuum
- source of electrons
- target for electrons
- high potential difference or voltage between the electron source and the target
what are the different parts of an x-ray tube?
- glass envelope
- cathode
- filaments
- focusing cup
- anode
- stator
- rotor
- bearings
- anode stem
- tungsten anode disk
- tube window
- tube housing
define glass envelope
- pyrex glass
- heat resistant glass
- houses the anode and cathode
- produces a sealed tight vacuum so air does not interfere with the x-rays
define protective housing
- lead lined metal protective housing
- absorbs photons that travel in different directions (other than the patient)
- contains an oil bath and cooling fans to help dissipate heat
define anode
- positive side of the tube
- also known as the target (for electrons)
- designed to dissipate heat
- made up of tungsten
define cathode
- negative side of the tube
- where thermionic emission is done
- where filaments are located
define induction motor
define filament
- source of electrons
- made up of tungsten
- located in the cathode to produce thermionic emission
why is tungsten used in the tube?
- contains 74 electrons
- has a high melting point, therefore, will not melt easily
define thermionic emission
- boiling off electrons
- with heat, electrons move at a rapid rate, forming an electron cloud made up of a strong negative charge
define space charge
- cloud of electrons
- the source of free electrons for x-ray production
define electron stream
when electrons move rapidly to the anode, attracted from its high positive charge
- pathway
what is the percentage of x-ray production when the electrons collide with the anode target?
- 99% heat
- 1% x-ray photons
what two types of interactions are produced after the collision with the anode?
bremsstrahlung and characteristic
define bremmstrahlung
- when an incoming electron gets attracted to Tungsten’s nucleus. as it gets closer, it slows down and changes directions
- from the change of direction, it loses energy, creating an x-ray photon
what does bremsstrahlung mean?
breaking radiation
define characteristic
- when an incoming electron collides with an electron in the (inner) k-shell
- ejects the electron from the orbit, producing an x-ray photon
- other electrons from the orbit will fill in the empty space
above 70 kVp, what is the percentage of bremss that are being produced?
85%
above 70 kVp, what is the percentage of characteristics that are being produced?
15%
are x-rays homogenous or heterogeneous?
heterogenous
why are xrays heterogenous?
they are made up of many different wavelengths and energies
what is the unit of measurement for x-ray energies?
kiloelectron volts (KeV)
define dual-focus tubes
tubes that contain two filaments instead of one
define focusing cup
hollow areas in the cathode that houses the filaments
define actual focal spot
- measurement of focal spot on target surface
- affects tube heat capacity
- bigger is better
- target area struck by electrons during an exposure
define effective focal spot
- measurement of vertical projection of actual focal spot
- affects image resolution
- smaller is better
- target area from which x-rays are projected toward the IR
list factors when a small filament is used
- directed to a small focal spot
- fewer x-rays
- higher spatial resolution
- used for small and medium patients
- less heat
list factors when a large filament is used
- directed to a large focal spot
- more x-rays
- less spatial resolution
- used for large and denser patients
- more heat
what is the function of the anode?
to dissipate heat
what are two types of anodes?
stationary and rotating anode
which anode is beneficial and why?
- rotating anode
- with the anode spinning, the heat is distributed all around the circumference of the disk, allowing the anode to last longer compared to a stationary anode
what is used to move the anode?
electromagnetic induction motor
what is the standard speed of the anode?
3,600 rpm (revolutions per minute)
what is the high frequency speed of the anode?
10,000 rpm
what causes the anode to “kick in” into a speed of 10,000 rpm?
- when a high technique is used
- high-speed rotation automatically engages when high exposure factors (kVp, mA, and exposure time) are reached.
- allows to dissipate heat more efficiently
define target angle
the slant of the anode surface
- angles between 7-17 degrees, witch 12 being the most common
what factors does the anode angle affect?
- tube’s heat capacity
- sharpness of the image
- maximum size of the x-ray beam
define line focus principle
*The size of the effective focal spot determines image resolution.
*The relative size of the effective focal spot is determined by the target angle.
*The steeper the target angle, the greater the difference between the actual and the effective focal spot sizes.
what is the size of the small focal spot?
0.6 mm
what is the size of the large focal spot?
1.2 mm
how does the anode angle affect the effective focal spot?
if the angle is steeper (more vertical/smaller), the smaller the effective spot will be
why is a small effective spot desirable?
for greater resolution
why is a large actual spot desirable?
to dissipate the heat of large exposures
why is a target angle of at least 12 degrees desirable?
- it will produce a radiation field that will cover a 14 x 17” IR at a distance of 40”
define anode heel effect
- uneven distribution of radiation intensity in the x-ray beam
- Because of the slanted face of the target, some x-rays will have to pass through more target material than others, depending on their direction.
*Variation in radiation intensity across the length of the radiation field
*Greater radiation intensity toward the cathode end of the field
*Only significant when using the whole beam (14- × 17-inch IR at 40 inches or full spine at 72 inches)
*Place thinner portion of body part toward anode end of tube
what examinations are used when applying the anode heel effect?
- femur
- thoracic spine
- chest
- lumbar spine
- abdomen
how should you place the patient when dealing with the anode heel effect?
place the patient so that the thinnest portion of the anatomy to be radiographed is toward the anode end of the tube
what happens if the anode heel effect is not used correctly?
the thinner portions of the anatomy appear too dark on the IR and the thicker portions will be too light.
what does kVp control?
- penetration
- contrast
- quality
what body part will require a high kVp?
larger and denser body parts
what body parts will require a low kVp?
small or low-density body parts
high kVp creates ___ contrast
low
- more shades of gray
low kVp creates ____ contrast
high
- low shades of gray (black and white)
what does mA control?
- volume
- quantity
- rate of exposure
- density
define mA
measure of the rate of current flow across the x-ray tube (number of electrons)
when mA is increased-
- the filament heat is increased
- more electrons are made
- more x-rays are produced
when mA is decreased-
- the filament heat is decreased
- less electrons are made
- less x-rays are produced
The density in the radiographic image is controlled by the-
mAs
- mA x sec.
what is the relationship between mA and x-ray prodcution?
- if mA is doubled, x-rays are doubled
- if mA is halved, x-rays are reduced by 50%
define exposure time
- length of time that the x-rays are turned on
- duration of the x-ray exposure
what is the unit of measurement in exposure time?
seconds or milliseconds
what is the relationship between exposure time and x-ray production?
- if exposure time is doubled, x-rays are doubled
- if exposure time is halved, x-rays are reduced by 50%
define milliamperage-seconds (mAs)
the unit used to measure the total quantity of electrons involved in an exposure
what is the formula for mAs?
mA x time (sec.) = mAs
define x-ray beam filtration
*Filter material placed between the tube housing port and the patient removes the long-wavelength radiation from the primary beam.
*Because this radiation does not have sufficient energy to penetrate the patient, the cassette, and the table, it does not contribute to the image.
*Filtration lowers patient dose significantly.
*Filtration decreases the average wavelength of the x-ray beam.
define filtration
the process of removing the long-wavelength photons from the x-ray beam
what is the primary purpose of filtration?
to reduce patient dose
what material is commonly used to filter out long wavelenghts?
aluminum
define added filtration
added aluminum
- One or more aluminum plates installed between the tube port and the collimator
define inherited filtration
- filtration provided by the glass of the tube and the surrounding oil
- “built in”
define total filtration
equal to the inherent filtration plus the added filtration
x-ray equipment operating at 70 kVp is required to have a total filtration of
at least 2.5 mm of Al equivalency at the source
define induction motor
- stator - current flow in it causes it to develop a magnetic field
- rotor - induced magnetic field causes rotor to rotate
what interaction makes up majority of the x-ray beam?
bremsstrahlung
a characteristic interaction needs a minimum of ____ kVp to be produced
70
what are factors of soft x-rays?
- low kVp
- low frequency
- long wavelength
- low energy
- slight penetration
what are the factors of hard x-rays?
- high kVp
- high frequency
- short wavelength
- high energy
- complete penetration
what are the three sections or subcircuits in the x-ray circuit?
- low-voltage circuit (primary)
- high-voltage circuit (secondary)
- filament circuit
what is the purpose of the low voltage/primary circuit?
supplies low voltage for operation of control console and for the variation of kVp
what is the function of the AC power supply?
it’s wired into the building, providing electric power from the local power company
- converts standard AC power supply from the wall outlet into the high voltage necessary for x-ray production
- to produce the high voltages needed to accelerate electrons toward the anode in the X-ray tube
what is the function of the main switch
- controls the power to the control console
- primary on/off switch
what is the function of the voltage composer?
- stabilizing and monitoring incoming voltage
- measures the incoming electrical voltage from the power source and automatically adjusts it to maintain a stable, precise voltage (typically 220 volts) needed for proper X-ray generation, ensuring consistent image quality regardless of fluctuations in the power sup
what is the function of the autotransformer?
- provides the means for kVp selection
- provides compensation for fluctuations in the incoming line voltage
- supplies power to other parts of the x-ray circuit
- controlling and adjusting the voltage supplied to the x-ray tube
- works by self-induction
- determines the voltage applied to the tube for x-ray production
what is the primary function of the autotransformer?
to vary the voltage to the primary side of the step-up transformer
what is the function of the kVp selector?
- controls the kVp
- controls how much voltage is set out to the rest of the primary circuit
what is the function of the exposure switch?
- closes the circuit
- allows electric current to flow through the primary side of the step-up transformer
- current is induced to flow through the secondary side of the transformer, creating voltage
- acts as the start button to generate x-rays
what is the function of the exposure timer?
- device that terminates the exposure and is set by the operator on the control console.
- controls the duration of the x-ray exposure
- the time it takes the disk to move from the on switch to the off switch.
what are the functions of the circuit breakers?
to protect against short circuits and electric shocks
what is the function of the step up transformer?
used to increase the voltage from the autotransformer to the kilovoltage necessary for x-ray production.
- the dividing line between the primary and secondary circuit
- primary coil is in the primary circuit
- secondary coil is in the secondary circuit
what is the function of the secondary circuit?
supplies high voltage to accelerate electrons for x-ray production
what is the function of the secondary coil of the step-up transformer?
- high voltage
- converts volts into kilovolts
what is the function of the milliampere meter?
monitors the x-ray tube current
what is the function of a rectifier?
- changes alternating current into direct current
- changing the current to flow in one direction
what is the function of the x-ray tube in the circuit?
produce x-ray photons
what is the function of the filament circuit?
- to supply a low current to heat the x-ray tube filament for thermionic emission of electrons
- supplies and controls heat needed for thermionic emission
- supplies electrons through step-down transformers
when is the filament circuit activated?
any time the operator adjusts the mA on the generator
what is the function of the mA selector/rheostat?
- controls amperage
- controls the amount of current flowing through the filament circuit of the x-ray tube
- adjusting the milliamperage
- controls filament temperature and the rate at which electrons are boiled off of the filament.
what is the function of the step-down transformer?
- increases current and decreases voltage
what are the different types of rectifiers?
- half-wave
- full-wave
define full-wave rectifier
- rather than the negative impulses being eliminated, the negative impulses become positive impulses
- negative impulses are “redirected” so that it all flows in one direction, leaving no gap during the waves
- uses the entire electric cycle
- all impulses flow in one direction
- occurs when using 4 diodes
what is an advantage if a full-wave rectifier?
the exposure time can be cut in half because of the doubling in x-ray output compared with half-wave rectification.
define half-wave rectifier
- eliminates the negative impulse of the electric cycle
- gap remains between each wave
what is the impulse rate of a full-wave?
120 impulses/sec.
define diode
an electronic device that permits current to flow in one direction only
how many diodes are used in half-wave rectification?
2
what is the impulse rate of a half-wave rectification?
60 impulses/sec.
how many diodes are used un full-wave rectification?
4
what are the different type of generators?
- single-phase
- three-phase
- high frequency
define single phase
- pulsating current that alternates from positive to negative during each electric cycle
- produces a pulsating x-ray beam
- lowest power and most basic
single phase x-ray generators are powered by-
a single source of AC current
define x-ray generators
converts the mechanical (KE) energy of the rotor to electrical energy
define three-phase generator
- more constant and efficient voltage source is provided by a three-phase power supply.
define ripple
- fluctuation of voltage
