Radiology 1 Flashcards
What are the two key pieces of legislation in place regulating the use of Ionising radiation?
- Ionising Radiation regulations 2017
- Ionising Radiation (Medical Exposure) Regulations 2017 - IRE(ME)R 2017
What is a radiograph?
An image produced by x-rays passing through an object and interacting with the photographic emulsion on a film. If a digital image is being formed, the x-rays affect a sensor or phosphor plate.
Atomic number
Protons
Neutron number
neutrons
Atomic mass number
neutrons + protons
Isotopes
atom with the same protons, different neutrons
Alpha particles
2 protons + 2 neutrons (helium nucleus)
Size: large
Charge: positive (+ve)
Speed: slow
Penetration: 1-2mm in tissue
Energy: 4-8 MeV
Damage potential: extensive ionisation
Beta particles
Electrons (fast electrons)
Size: small
Charge: negative (-ve)
Speed: fast
Penetration: 1-2 cm in tissue
Energy: 100keV - 6MeV
Damage potential: ionisation
Gamma rays
Electromagnetic radiation
Size: Nil
Charge: Nil
Speed: very fast
Penetration: can pass through tissue
Energy: 1.24 keV - 12.4 MeV
Damage potential: ionisation
What type of x-rays are used in dentistry?
Identical to gamma rays - with lower energy values.
No charge, weight or mass.
Very fast.
Cause ionisation.
Energy is measured in…
electron volts - eV
Frequency is measured in…
Cycles per second or Hertz
Wavelength is measured in…
metres or nanometers = 10 -9
Visible light range
400-700nm
What is a volt?
The SI (System internationale) unit of electric potential difference is the volt.
What is 1 volt?
The potential difference between 2 points on a conducting wire, carrying a constant current of 1 amp, when the power dissipated between the points is 1 watt.
How can voltage be thought of conceptually?
The “power” or “force” that causes a current to move along a wire or electrons to move across a gap from a cathode to an anode.
What is happening when electricity is flowing through a wire?
Electrons within the wire coils are vibrating, this produces heat, wire becomes red hot giving off light.
Radiant heat warms air molecules resulting in warming effect.
Heat produced is proportional to current and voltage.
X-rays in terms of energy conversion
Electricity is converted into x-ray generation (slightly inefficient as much of the conversion of energy produces heat).
