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Radiology
Study of x-rays and techniques used to produce radiographic images
X-radiation
High energy radiation produced by collision of electrons with tungsten target
X-ray beam
Beam of energy that can penetrate objects and record image shadows on film
Radiograph
Image produced by X-Ray beam creating shadows
As Low As Resonably Achievable
ALARA
William Conrad Roentgen. Received first noble prize in 1901.
Who discovered X-rays?
Roentgen Rays. Then changed to X-rays, the X representing the unknown
What was the original name of X-rays?
Kodak
Who produced machine wrapped film packets in 1919?
Emulsion coating
In early years of film, only one side had ___________ ___________. Required long exposure times
Emulsion
As film improved, both sides were coated with this that allowed for much shorter exposure times
1987
When was digital dental radiography introduced?
Digital sensors
This replaced film and required even less radiation exposure?
Uses of dental imaging
Detect lesions, diseases, and conditions of teeth that cannot be seen clinically.
Confirm suspected disease
Localize lesions or foreign objects
Provide info during dental procedures
Evaluate growth and development
Observe changes due to caries, perio and trauma
Document the condition of the patient
Development of clinical treatment plan
Electrons
Negative charge
Protons
Positive charge
Neutrons
No charge, neutral charge
Atom
This has a nucleus made up of protons and neutrons
An ion
When an atom gains or loses electrons, it becomes?
Ionization
The formation of ion pairs
Ionizing radiation
Radiation that produces ions (X-rays, gamma rays, cosmic rays)
Particulate and electromagnetic radiation
What are the two types of ionizing radiation?
Particulate radiation
Travel in straight lines at high speeds (HAVE MASS)
Electromagnetic radiation
Movement of wave-like energy through space (NO MASS)
Combination of electric and magnetic fields.
Electromagnetic waves
Radiation moving in wave like pattern
Wavelength
Distance between two adjacent wave crests
Frequency
Number of waves that pass given point per unit time
Velocity
Speed of the wave
100 meters
How many meters are radio waves?
1 meter
How many waves is a TV?
.0000000001 meter (.1nm)
How long is the dental X-ray wave?
(Shorter the wavelength, the stronger the radiation)
Properties of X-rays
-invisible
-no mass or weight
-no charge
-travel at speed of light
-travel in waves and straight lines
-cannot be focused to a point
-penetrate liquids, solids and gases
-absorbed by matter
-interact with matter, causing ionization
-cause certain substances to fluoresce
-can produce image on receptor
-cause biologic changes to living cells
Insulating oil
Surrounds the X-ray tube and transformers inside the tubehead
Absorbs the heat created by the production of X-rays
Tubehead seal
Aluminum or leaded glass covering tubehead
Seals in oil and filters the x-ray beam
Transformers
Control voltage of incoming electricity
Aluminum disks and lead collimator
Added for filtration
X-ray tube
Heart of it all!! Glass vacuum tube inside tube head.
Leaded glass housing
Vacuum tube that prevents x-rays from escaping in all directions
Has a small non-lead window that allows x-rays to exit
Cathode
Negative electrode
Supplies the electrons to produce x-rays
Consists of Tungsten wire/filament-when heated produces electrons
Molybdenum focusing cup--directs electrons toward target on anode
Anode
Positive electrode
Consists of: Tungsten target-stops electrons so energy can be converted to x-rays
Copper stem: Dissipates heat away from tungsten target
Electricity
What is needed to produce X-rays?
Filament circuit
Low voltage to filament of x-ray tube
-Generates source of electrons needed to produce x-rays
3-5 volt
-Controlled by the milliampere setting (mA)
High voltage circuit
-Accelerates the electrons from the cathode to anode target
-65,000 to 100,000 volt
-Controlled by the Kilovolt setting (kV)
Transformer
Located in the tube head to increase or decrease voltage
Step down transformer
Heats the Tungsten filament to form electron cloud
-Brings 110 or 220 volt line to a 3-5 volt
Step up transformer
Increases voltage to propel electrons toward target
-Bring the 110 to 220 volt line to 65,000-100,000 volt
Production of dental x-rays
Prior to pushing exposure button...
-Electricity from room supplies power
-Current is directed to the filament circuit and step-down transformer
-Filament circuit uses 3-5 volts to heat tungsten filament in cathode
-Electrons stay in a cloud around the filament Thermionic Emission
-Stays in a cloud until the button is pushed (high volatge activated!!)
The high voltage circuit activated
When the exposure button is pushed, this is activated
The molybdenum cup in the cathode
This directs electrons to tungsten target in anode
X-rays!
1%, remaining 99% is lost as heat--dissipated in copper stem
When electrons strike tungsten target, energy is converted into what?
About what percent is converted to x-rays?
Unleaded glass window
Small number of the x-rays exit the x-ray tube through?
Aluminum disks
X-rays then travel through the tube head seal and?
Lead collimator
X-ray beam size is restricted by?
PID!
X-ray beam, exits tubehead at the opening of?
General radiation (Bremsstrahlung Radiation)
Majority of production
-Produced when high-speed electrons are stopped or slowed down by tungsten atoms of dental x-ray tube
Characteristic Radiation
Produced when a bombarding electron from the tube filament collides with an orbiting K electron of the Tungsten target
No interaction
Coherent scatter
Photoelectric effect
Compton effect
What are the interactions of x-rays?
Coherent scatter
New x-ray scattered in different direction than original 8%
Photoelectric effect
X-ray is absorbed and vanishes (30%)
Compton effect
New, weaker x-ray is formed and scattered in new direction (62%)
Kilovoltage (kV)
Determines the speed of electrons and QUALITY of X-rays
-Shorter wavelength=more penetrating power=high quality beam
Increase speed of electrons
-Creates a more penetrating beam with shorter wavelength
Increase in kV=?
65-100kV
Dental radiography uses how much kV?
Darker image
Lighter image
Image density (overall darkness of an image)
-Increase kV=?
-Decreased kV=?
Image contrast
Difference in dark and light areas
High contrast image
Black/white with few shades of gray
Short scale contrast
Good for caries detection
For contrast: Low kV (65-70)=?
Low contrast image
Many shades of gray
Good for detecting perio and periapical disease
For contrast: High kV (greater than or equal to 90)=?
Darker!!
When kV is increased the image becomes ____________, decrease exposure time. BOARD ALERT
CONTRAST
kVp affects the ______________ of an image! BOARD ALERT
Milliamperage (mA)
Determines the number of electrons passing through the cathode filament. BOARD ALERT
Increasing
________________mA= increasing temp of the cathode filament
Increased
Increased number of electrons = _______________ number of x-rays
More dense
Darker radiograph = ?
7-15 mA
In dental radiography what is the mA that is used?
Image density
Overall darkness of an image
Darker
Increased mA= ____________ image
Lighter
Decreased mA= ____________ image
Decreased
When mA is increased, exposure time must be _____________?
Kilovoltage peak
Higher kVp= Increased intensity of X-ray beam
Milliamperage
Higher mA= X-ray with more energy, increasing the intensity of the x-ray beam
Exposure time
Longer exposure time = More x-rays and more intense x-ray beam
Distance
Increase in distance = reduction of intensity in x-ray beam
Inverse Square Law
Intensity of radiation is inversely proportional to the square of the distance from the source of radiation
1/4 as intense
When the distance is doubled, the beam is?
4 times
When the distance is halved, the beam is ________ times as intense
Half value layer (HVL)
The thickness of material that, when placed in the path of the x-ray beam, reduces are exposure rate by one-half
-Aluminum filters are placed in the path of the beam inside the x-ray tube head.
Radiolucent
-Area of image that is dark or black
-Structures in this area were not dense (skin, air, decay)
Radiopaque
-Area of image that appears white or light gray
-Structures in this area were dense and absorbed/blocked the x-ray beam
Sharpness
-Distinct outlines of an object
-Lack of sharpness=penumbra=fuzzy or blurred area around image.
Focal spot (Smaller= sharper)
Film composition (Smaller crystal size= Sharper)
Movement (causes less sharpness)
Sharpness is influenced by?
Magnification is influenced by:
Short PID-Short target/receptor distance
Increased object/receptor distance
Distortion
Variation from true size/shape of object being imaged
Influencing factors: Object/film alignment-Must be parallel to each other
X-ray beam angulation-Beam must be perpendicular to tooth and film
Ionizing
All of this type of radiation is harmful--Dental exposure is minimum
Free radical formation
Most common type of cell damage in humans (BOARD ALERT)
-Created by ionization of water in cells
Latent period
Period of time from exposure to visible damage
More radiation/faster dose = Shorter ____________ period
EX: Sunburn, aggressive radiation therapy
Less radiation/slower dose = Longer latent period
Proper radiation doses allow for tissue repair
Young cells
Most sensitive are rapidly dividing and?
Blood cells
Bone marrow
Reproductive cells
Intestinal mucosa
Skin
Lens of eye
Oral Mucosa
What are the radiosensitive cells? (BOARD ALERT)
Mature bone
Nerve
Muscle
Salivary Glands
Thyroid Gland
Kidney
Liver
Radioresistant Cells
Coulombs/kg
Exposure: Amount of radiation in the air
Gray (Gy)
Dose: Amount of radiation absorbed by the tissue
Sievert (Sv)
Dose equivalent: Measurement of the effect on the tissue
Note 
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