Review Chapters 1-4 Flashcards
What are the radiation characteristics
X-ray beam quality, quantity, and intensity
Define quality
The mean energy or penetrating ability of the X-ray beam
What controls the quality and why?
KVP. Because the kvp controls the energy and wavelength of the x-ray beam
What is voltage and how is it measured?
Voltage is the measurement of electrical force that causes electrons to move from the negative cathode to the positive anode. Measured in KV
What regulates the speed and energy of the electrons?
Voltage, or kilovoltage KVP, KV
What is density?
Overall darkness or blackness of an image
What would make a darker image?
Raising the KVP or MA
What does contrast refer too?
How sharply dark and light areas are differentiated or separated on an image
If an image has high contrast will it have many shades of grey?
No it will have more dark areas
When would you want a high contrast image specifically?
For Bitewings
If you lower the KVP what happens to you contrast of your image?
Your contrast increases
What does exposure time refer to?
The interval of time during which X-rays are produced
How is the exposure time measured?
In impulses
I impulse occurs every?
1/60 of a second
Therefore 60 impulses occur in 1 second
If the KVP is decreased the exposure time?
Exposure time should be increased
Because if you lower the KVP you will have less penetrating beam power so you will need for X-ray time on the matter you are trying to capture
If KVP increased then exposure time?
Exposure time increases
What does exposure time effect?
Contrast and density which ultimately effects the overall quality
If someone had a hard time staying still during film exposure what settings would you change?
The mA could be increased while the exposure time is decreased
What is mA usually preset too?
7 mA
mA increases the heating of what part in the tube head?
Tungsten filament at the negative pole cathode
What does mA do?
Increases quantity of photons (X-rays) by increasing the number of electrons produced in the cathode
Does a high mA increase the temperature?
Yes
Increase in mA has what effect on density?
Increase in mA increases overall density results in a darker image
Decrease in mA has what effect on density?
Decreased overall density
Resulting in a lighter image
What should you do with exposure time for small children?
Decrease it
What is intensity?
Product of quantity and quality per unit of area per unit of time of exposure
What are the several distances you must consider when exposing a dental radiograph?
Target surface distance
Target object distance
Target receptor distance
Object film distance
What is the relationship between distance and intensity of radiation called?
Inverse square law
If the distance of the X-ray tube increases what happens to intensity?
The intensity decreases
Think of a flashlight on a wall
If the PID length is changed from 8 to 16” how does this increase in source-to-receptor distance affect the intensity of the beam?
The beam will be 1/4 as intense
What is the purpose of the aluminium filter?
Reduce intensity and remove the low Energy X-rays from the beam
What is HVL?
Half value layer.
Refers to the thickness of aluminum when placed in the path of the X-ray beam reduces the intensity by 1/2
Electromagnetic radiation
Travels at the speed of light
Travels as both particle and a wave
Possesses different measurable energies: frequencies and wavelengths
Wavelength
Measured by the crests (peaks) of one wave and crest of the next
Determines entertainment and penetrating power of radiation
What is frequency
Number of wavelengths that pass a given point in a certain amount of time
High frequency=short wavelength
Short frequency=long wavelength
What is x-radiation
High energy, ionizing electromagnetic radiation
X-ray
Posses particles of waves and particles
Photons
Travels at the speed of light
Posses short wavelengths and high frequency
X-rays travel in straight lines and can be deflected or scattered
Cause ionization in tissue
Where are X-rays produced?
Tube head
What is in the tubehead?
Cathode terminal anode terminal
What is inside the tube head envelope?
Lead and the tubehead is insulated by surrounding oil
Where is the molybdenum and what is its purpose?
It is in the cathode and embed’s the tungsten filament. It is responsible for directing the electrons to the tungsten target of the anode
Incandescence
The cool becomes white with the generation of heat
What is the anode made of
Copper rod to dissipate heat and tungsten target
What is the collimator?
Lead plate with a central hole that fits directly over the opening of the metal housing where the X-rays exit
What restricts the size of the X-ray beam
Collimator
What is exposure time affected by
Radio graphic technique
Type of X-ray film
Tissues being radiographed
Target film distance
An X-ray machine is capable of generating radiation?
1/60 of a second
Does alternating current flow in continuous direction?
No
What are transformers?
Devices used to increase or decrease the voltage in an electrical circuit
What do transformers do?
Transformers alter the voltage of the incoming electrical current and then route the electrical energy to the X-ray tube
What are the 3 transformers used?
Step down
Step up
Autotransformers
General radiation
Consists of many different energies and wavelengths
Occurs when an electron hits the nucleus or comes close to the nucleus of the tungsten atom
Primary radiation
X-ray beam that is produced at the target of the anode and exits the tube head
Referred to as primary or useful beam
Secondary radiation
X-radiation that is created when primary beam interacts with matter ex: tissues of head
Less penetrating than primary radiation
Scatter radiation
Form of secondary
Compton scatter
Ejected electron is known as Compton or recoil electron possessing a negative charge
Compton accounts for 62% of the scatter that occurs in radiography
Who first discovered X-rays
Dr.wilhelm Conrad roentgen
Who introduced bisecting technique
Weston price
Who introduced bite wing tech
Howard Riley raper
Who introduced paralleling technique
C.Edmund Kelly
