Radiology basics

Question 1

Describe how a radiograph is formed.

Answer 1

x-ray passes through an object, interacts with the photographic emulsion on a film.
- In digital images, the x-ray affects a sensor or phosphor plate

Question 2

Why are radiographs useful in dentistry?

Answer 2

• x-rays interact with mineralized tissue such as enamel and dentine, when caries causes demineralization, we can see it on radiograph

Question 3

What is the difference between an intra-oral and extra-oral radiograph?

Answer 3

• intra-oral: film placed in the mouth and the x-ray source is directed at it from the outside - produces intramural images
• extra-oral: both radiation source and image receptor outside the mouth

Question 4

give examples of intra oral and extra oral radiographs

Answer 4

• intra-oral: occlusal, bitewing, periapical

- extra-oral: DPT/OPT/OPG

Question 5

When were radiographs first used in dentistry and what for?

Answer 5

• 1896 for decay and periapical pathology

Question 6

why are radiographs used despite the fact that it is dangerous / ionizing radiation?

Answer 6

• diagnostic effects> adverse effects of x-rays

Question 7

What is an atom? what is it made up of?

Answer 7

• atoms are building blocks of life

- consist of internal nucleus containing protons and neutrons, surrounded by a shell of electrons

Question 8

why does an atom have no overall charge?

Answer 8

• protons: positive
• neutrons: neutral
• electrons: negative

no overall charge because NO. protons = NO. electrons

Question 9

Describe the nature of electrons within energy shells, name the shells and how many electrons they contain.

Answer 9

• electrons sit in shells surrounding the nucleus
• shell names: k, L, M
• K= 2, L = 8, M=18

Question 10

How can an electron be removed from an atom?

Answer 10

• Energy is required to overcome the binding energy, binding energy being the energy caused by attraction of negative electrons to positive protons

Question 11

what is atomic number, atomic mass number and neutrons number?

Answer 11

• atomic: protons
• neutron: neutrons
• Mass: protons + neutrons

Question 12

what are isotopes?

Answer 12

• Atoms with the same number of protons but different number of neutrons

Question 13

what are radioisotopes?

Answer 13

• isotopes with unstable nuclei which undergo radioactive disintegration - atoms splits into smaller, more stable ones
• this changes the atoms from one substance to another

Question 14

what is an ion?

Answer 14

• charged atom caused by loss or gain of electron/ becomes ionised
• positive ion: lost electrons
• negative ion: gained electrons

Question 15

What are gamma rays?

Answer 15

• part of electromagnetic spectrum,
• no charge, mass or size
• travels very fast
• can penetrate through tissue and can cause damage due to ionization

Question 16

Why is ionization a problem? gives an example of a condition caused by ionization

Answer 16

• it can damage living cells
• cataracts: the lens of the eye develops cloudy patches causing blurred vision- happens because cells covering posterior surface of lens are damaged

Question 17

how does ionizing radiation cause damage to cells?

Answer 17

• when ionizing radiation passes through a cell, there is a transfer of energy to the cell which removes electrons from atoms and molecules in the process of ionization. This can directly damage the cell
• ionisation tiggers chemical reactions which damage the cell including the DNA

Question 18

how does a basic circuit work?

Answer 18

• current passes along a wire through vibration of electrons
• the electrons pass from negative end (anode) to positive end (cathode)

Question 19

energy can’t be created or destroyer, it is transferred form one form to another, which form transfers to x-rays? what is the issue with this change in energy?

Answer 19

• electricity is converted to x-ray

- not efficient because most of the conversion of energy produces heat