Radiation physics

Radiation

The transmission of energy through space or matter

-particulate radiation

-Electromagnetic radiation

What are the two forms of radiation?

Shells

What are the energy levels called electrons are located in around the nucleus

Closer to the nucleus

Where is the binding energy higher in electrons? Closer to the nucleus or farther away.

Atomic nuclei or subatomic particles

What two things does particulate radiation consist of

Yes

Does particulate radiation have mass and charge?

High velocity

What type of velocity are particulate radiation particles moving at?

May have a positive, negative, or neutral charge

What charge do particulate radiation particles have?

Alpha, beta, cathode rays

What are three examples of particulate radiation?

Electromagnetic radiation

The movement of energy through space as a combination of electric and magnetic fields

No

Does electromagnetic radiation have mass and charge?

The speed/velocity of light

At What does electromagnetic radiation travel?

Non-ionizing and ionizing

What are the two categories of electromagnetic radiation?

Ionizing

The type of electromagnetic radiation that has sufficient energy to remove an orbital electron from an atom

-wave theory

-Particle or quantum theory

What are the two theories that explain characteristics of electromagnetic radiation?

Wave theory

The theory of electromagnetic radiation where radiation is propagated in the form of waves

Electrical and magnetic fields oriented in planes at right angles to one another and oscillating perpendicular to the direction of movement

In the wave theory, what do the waves consist of and where are they oriented?

Velocity

Wavelength x frequency

Quantum theory

The theory of electromagnetic radiation that is depicted as small bundles of energy

Photons

The small bundles of energy that radiation is depicted as

At the speed of light and contains a specific amount of energy

How does each photon travel and what does it contain?

KeV

What is the specific amount of energy called that a photon contains?

No

Do photons have a mass or charge

-short wavelength

-High frequency

When photons have high energy, what is the wavelength & frequency

-Long wavelength

-low frequency

When photons have low energy, what is the wavelength, and frequency?

Energy

Planck's constant x frequency

Radiographic tube housing

What x-ray machine generates the x-ray?

The operating console/control panel

Which x-ray machine adjusts the radiation

Vacuum environment

What type of environment is the x-ray tube?

Cathode(-) and anode (+)

What two things does the x-ray tube contain

-Tube current

-Tube voltage

What are the two characteristics of the power supply of radiographic tube housing

Tungsten filament

On the cathode (-), what is the source of electrons?

Molybdenum focusing cup

The concave reflector that focuses the electrons on the cathode toward the anode

-generation of electrons

-Production of high-speed electrons

-Focusing of electrons

-Stopping of high-speed electrons at the target

What are the four steps of the cathode transferring the electrons toward the anode?

Tungsten target

What is the target called where the high speed electrons stop?

High atomic pressure, high melting point, high thermal conductivity, and low vapor pressure

What is the atomic number, melting point, thermal, conductivity, and vapor pressure of the tungsten target

Copper

A good thermal conductor that dissipates heat from the tungsten target

Focal spot

The area on the target to which the focusing cup directs the electrons from the filament

Focal spot

The place to convert the kinetic energy of the electrons from the filament into x-ray photons

X-rays

When the kinetic energy is converted into x-ray photons, what does this generate?

About about 20°

What angle is the target place at to the electron beam?

-smaller, effective vocal spot for an increase in sharpness of the image

-Larger actual focal spot for heat dissipation

What are the two characteristics of the effect of an angled target?

-sharpness of the radiographic image

-the heat generated per unit target area

The lower the focal spot size, the higher the what? (2 things)

Glass envelope/glass tube

What provides a vacuum environment and withstand tremendous heat

X-ray tube window

What allows the maximum emission of x-rays and minimum absorption by the glass?

Lead lined metal casing

What type of casing does the protective housing have?

-provides mechanical support

-Prevents excessive radiation exposure and electrical shock

What two things does the lead lined metal casing allow for the protective housing

Power supply

What creates a high voltage and a low-voltage circuit with transformers?

Provides a low-voltage current to heat the x-ray tube filament

What does the power supply do that makes electrons available?

Generates a high potential difference between the anode and cathode

What does the power supply do that moves the electrons?

Direct vs alternating

What are the two types of currents in the power supply?

AC (most common) and DC/constant potential

What are the two types of dental x-ray machines?

Self rectification

The process of converting an alternating current voltage into a direct current voltage

-mA

-kV

-Control

What are the three controls on the operating console/control panel?

Millaperage (mA)

What controls the output of the step down transformer by limiting and varying the amount of current from the AC power source

Provide a low voltage current to heat the x-ray tube filament

What does the mA do to make the electrons available?

Increases temperature and increases number of electrons

What does increasing the mA due to the temperature and number of electrons

kVp

What selects the appropriate output of the auto transformer to supply the high-voltage step up transformer

Generate a high potential difference between the anode and cathode

What does the KVP do to move the electrons?

Timer

What determines the length of time electrons will flow from the cathode to the anode, and thus the number of x-rays produced

-impulses

-seconds

-anatomic

What are the three parts of the timer?

-x-rays (1%)

-Thermal radiation (99%)

What two things is the kinetic energy of electrons converted to

-Bremsstrahlung radiation

-characteristic radiation

What are the two types of radiation that the x-rays produce

The heat loading capacity of the tube

What should you be aware of with thermal radiation?

Bremsstrahlung radiation

The stopping or slowing of high-speed electrons at the target interaction with new target nucleus directly or close to a nucleus

-Direct hit

-near Miss

What are the two types of bremsstrahlung radiation?

Bremsstrahlung radiation

The primary source of radiation from an x-ray tube

Continuous

What type of spectrum of energy is the bremsstrahlung radiation

-varying voltage across tube

-varying energy of electrons

-varying distance from nucleus

What three things varies in the continuous spectrum of energy of bremsstrahlung radiation

Characteristic radiation

Radiation originating in an atom following the removal of an electron

Characteristic radiation

A minor source of radiation from an x-ray tube

Energy of the resulting characteristic x-ray photon

What is the result of the difference in the binding energies of orbital electrons?

Quantity, quality, shape

What are the three characteristics of the x-ray beam?

Quantity

The number of photons generated; density of photons

Higher

The higher the quantity, the __________ x-ray photons

Quality

The mean energy of photons generated, the maximal energy of photons generated; contrast

Higher

The higher the quality, the __________ penetration power

X-ray beam, quantity and quality

What are the two factors controlling the x-ray beam?

-exposure time

-millamperage (mA)

-Kilo voltage

-filtration

What are the four characteristics of x-ray beam quantity?

-kilovoltage

-filtration

What are the 2 characteristics of x-ray beam quality?

Filtration

Process of selectively removing x-rays from the beam

Low energy or non-penetrating x-rays

What are filtered from the beam?

Higher; lower

The higher the filtration, the __________ quality and ___________ quantity

-inherent

-Added

-Total filtration = inherent + added

What are the three types of x-ray filtration

Inherent filtration

The type of filtration that is part of the x-ray tube design and can't be removed like glass/metal filters

Added filtration

The type of filtration that is interchangeable, metal sheets, like aluminum/copper

Collimination

The process of restricting the size and shape of the x-ray beam

-diaphragm

-Cone or position indicating device (PID)

-film holding instrument

What is collimination achieved by?

Inverse square law

The intensity of an x-ray beam is inversely proportional to the square of the distance from the target

I1/I2 = D2^2/D1^2

What is the inverse square law formula

The product of tube current and time

The intensity of radiation produced is expressed as what

Interaction with matter it encounters

The intensity of an x-ray beam is reduced by what

Beam attenuation

The reduction of beam intensity

-absorption

-scattering

As a dental x-ray beam travels through matter, some photons are removed. What two things happens to them?

Half value layer

The thickness of an absorber, such as aluminum required to reduce by 1/2 the number of x-ray photons passing through it

-thickness of the absorber

-Mass of the absorber

-Energy of the beam

What three things does the absorption of the beam depend on?

More

The thicker the object, the _______ photons are absorbed

More

The higher the density of the object, the __________ photons are absorbed

Low energy photons are much more likely than high energy photons

What type of photons are much more likely to be absorbed