Introduction

Question 1

What is a radiograph?

Answer 1

• 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 a phosphor plate

Question 2

Who discovered X-rays?

What was the first x-ray image and when?

When were radiographs first used in Dentistry?

Answer 2

Wilhelm Conrad Roentgen - November 1895

• image sof his wifes hand - December 1895
• first used in dentistry in 1896 and could detect caries and periapical pathology

Question 3

What is an atom made up of?

Comment on the shells:

Answer 3

Nucleus:

• protons (positive charge)
• neutrons (no charge)

Electrons - negative charge: orbit around nucleus in different energy shells:

• K, L, M outer shells
• move in predetermined shells with different energy levels
• can move from shell to shell but cannot exist between shells: forbidden zone
• energy is required to remove electrons fron atom and must overcome binding energy which keeps it in its shell
• greatest binding energy on outermost shells

Question 4

What are isotopes?

Radio-isotopes?

What are ions?

Anion?

Cation?

Answer 4

Isotopes: atoms with the same number of protons but different number of neutrons

Radio-isotope: isotopes with unstable nuclei which undergo radioactive disintegration

Ions: charged atom or molecule, number of electrons do not equal number of protons

Anion: negative charge if more electrons

Cation: positive charge if more protons

Question 5

What is an alpha particle?

Beta particle?

Gamma radiation?

Answer 5

Alpha particles:

• 2 protons, 2 neutrons (helium nucleus)
• large, positive charge, slow, penetrate 1-2mm in tissue, cause extensive ionisation

Beta particles:

• fast electrons, snall, negative charge, fast, 1-2cm penetration in tissue, ionisation damage

Gamma rays: electromagnetic radiation

• very fast, can pass through tissue, also cause ionisation

Question 6

When does ionisation become a problem?

Answer 6

• when it occurs in living cells
• can cause damage to tissues e.g. cataracts
• can cause damage to DNA directly or produce chemicals that do damage e.g. tumours or cancer

Question 7

Give an overview of the electromagnetic spectrum:

Answer 7

• stream of photons that have no mass
• travel at speed of light 3.0x10⁸
• photons can have ddifferent amounts of energy –> affects properties
• energy measured in eV
• frequency - cycles per second or Hertz
• wavelength measured in metres or nm
• visible light 400-700nm

Question 8

What is the domestic electricity supply?

Answer 8

• 220-240V
• 50 Hz
• 13 amp

1V is the potential difference between 2 points on a conducting wire carrying a constant current of 1amp, when the power dissipated between the points is 1 watt