Intro to Dental Radiography Flashcards
What is a radiograph?
An image produced by X-rays passing through an object and interacting with the photographic emulsion on a film.
If it is a digital image being formed, what are the X-rays affecting?
The X-rays are affecting a sensor or a phosphor plate.
Why are radiographs useful?
They allow us to look inside the body, particularly at mineralised tissues.
When were radiographs discovered and by who?
Wilhelm Conrad Roentgen discovered X-rays in 1895.
When were radiographs first used in dentistry?
In 1896.
What does an atom consist of?
A positively charged nucleus surrounded by energy shells containing orbiting electrons.
What makes up the Nucleus?
+ve protons and neutral neutrons.
What are the maximum numbers of electrons contained in the shells?
K=2, L=8, M=18, N=32, O=50
What is the area between shells known as?
The Forbidden Zone, as electrons cannot exist between shells.
How can an electron be removed from its shell?
Enough energy to overcome the “binding energy” which keeps the electrons in their shells.
What is Z?
The atomic number = the number of protons.
What is N?
The neutron number = the number of neutrons.
What is A?
The atomic mass number = the number of protons and neutrons.
What are Isotopes?
Atoms with the same atomic number (Z), but different neutron number (N).
What are Radio-isotopes?
Isotopes with unstable nuclei which undergo radioactive disintegration.
What are Alpha particles made up of?
2 protons and 2 neutrons.
Describe an alpha particle in relation to: Size Charge Speed Penetration Energy Damage Potential
Size = Large Charge = Positive (+ve) Speed = Slow Penetration = 1-2mm in tissue Energy = 4-8 MeV Damage Potential = extensive ionisation
What are Beta Particles?
Fast electrons
Describe a beta particle in relation to: Size Charge Speed Penetration Energy Damage Potential
Size = small Charge = negative (-ve) Speed = fast Penetration = 1-2cm in tissue Energy = 100keV - 6MeV Damage Potential = ionisation
What are Gamma Rays?
Electromagnetic radiation
Describe Gamma Rays in relation to: Size Charge Speed Penetration tissue Energy Damage Potential
Size = Nil Charge = Nil Speed = very fast Penetration tissue = can pass through Energy = 1.24keV - 12.4MeV Damage Potential = ionisation
Describe X-rays used in dentistry (7 points).
- They do not occur naturally
- Not involved in radioactive decay
- Identical to Gamma Rays - though not such high energy values
- Not particulate
- No charge
- Very fast
- Cause ionisation
What affects the properties of photons?
Their energy, photons can have different amounts of energy.
What is energy measured in?
Electron Volts (eV)
What is frequency measured in?
Cycles per second or Hertz (Hz)
What is wavelength measured in?
Metres or nanometres, (10^9)
What is the range of visible light in nanometres?
400-700 nanometres
X-rays, among others, are so small they are described by their…?
Energy (eV)
Describe domestic electricity supply in relation to: Energy Frequency Current What circuits can be fused with
220/240 Volts
50 Hertz
Usually a 13 amp current
Fuses of either 3, 5 or 13 amps
What is another name for Potential Difference?
Electromotive Force
Potential difference (SI) is measured in?
Volts
When the power dissipated between two points on a conducting wire is 1 Watt, what is the SI?
1 Volt is the potential difference between two points on a conducting wire, carrying a constant current of 1 amp.
How is a current passed along a wire?
By the vibration of electrons, from -ve to +ve.
When electricity flows, what happens to electrons?
The electrons within the wire coils vibrate, causing electricity to pass through the whole length of the coils.
What do vibrating electrons produce and therefore cause to happen?
Vibrating electrons produce heat, causing the wire to become red hot and give off light.
What happens when a wire becomes red hot?
Radiant heat cause the movement of air particles, the surrounding are becomes hot.
The heat given off by the wire is proportional to what?
The current and voltage used.
