Week 2 Lecture Objectives Flashcards
Direct Current
Electrons flow in one direction
Alternating Current
Electrons travel in one direction, stops, reverse and go in the opposite direction.
Filament Circuit
Provides source of electrons by heating the filament
3-5 volts, controlled by (Ma)
High Voltage Circuit
Provides voltage required to accelerate electrons to anode at high speeds.
65,000-100,000 volts
Controlled by (Kv)
Transformer Step Down
Heats the filament circuit.
Controlled by Ma
Lots of coils in primary to less coils in secondary.
Goes from 110 to 3-5 volts
Transformer Step Up
Controls the high voltage circuit by (Kv)
Less coil in primary to more coils in secondary.
110 Volts to 65,000-100,000 Volts
Auto Transformer
Ability to alter Kv
single same amount of coils throughout serves as the primary and secondary coils
Quantity
# of x-ray photons in a beam controlled by Ma
Quality
the Energy/penetration ability of x-ray photons
kVp
Distance
The size of the Beam
Rate
Exposure Time,influences Quantity
Beam Intensity
Quality and Quantity together
mA and Kvp relationship with exposure time
Inversely related
KVP/mA goes up exposure time goes down
Inverse Square Law
As one variable increases the other decreases
if a distance is double = 1/4 as intense
if a distance is tripled= 1/9 as tense
if a distance is quadruples= 1/16 as intense
Short Wavelength
Greater penetration
High energy
High frequency
Goes through body
Long Wavelength
Lower penetration
Low energy
Low frequency
Absorbed
Which wavelength is better? short or long
SHORT
Half Value Layer
Located in tubehead thickness of absorbing material, usually aluminum. necessary to reduce x-ray intensity by 1/2
Primary Radiation
Penetrating x-ray beam produced at the tungsten target of the anode that exits at the tube head.
comes out from machine before it touches anything
Secondary Radiation
Created when the primary beam interacts with matter.
soft tissue head,bone of skull and teeth
beam interacts with matter, goes passes through body
Scatter Radiation
x-ray photon deflects from its path by interaction with matter.
Absorbed Completely (photoelectric effect)
Absorbed Completely, energy transfer from photon to matter
Produce light/ white areas on film
ex: enamel, cortical bone, metallic fillings
What is “pass through” in secondary radiation?
No interaction
Producing dark areas on film
ex: soft tissue, pulp, PDL
Compton Scatter
Photon strikes loosely outer shell electrons, ejecting some from obit. x-ray photon loses energy, goes in another direction
ex: film is foggy
Coherent Scatter
Low energy photon path altered by matter, changes direction but no energy transfer
Attenuation
Reduction in intensity of x-ray beam
Radiopaque Area
High absorption white area on film
Radiolucent Area
Low absorption of x-ray photons, black area on film
What has affects on absorption
Wavelength, Density, Thickness, Atomic number of material
Milliamperage (mA)
Regulates temp of cathode
determines the number of photons in a beam
Kilovolt Peak (kVp)
Regulates speed/energy of electrons
determines the Energy of each photon penetration ability
What are the two circuits necessary for production of x-rays in the x-ray tube
Filament circuit and high voltage circuit
