Radiology basics Flashcards
Describe how a radiograph is formed.
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
Why are radiographs useful in dentistry?
- x-rays interact with mineralized tissue such as enamel and dentine, when caries causes demineralization, we can see it on radiograph
What is the difference between an intra-oral and extra-oral radiograph?
- 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
give examples of intra oral and extra oral radiographs
- intra-oral: occlusal, bitewing, periapical
- extra-oral: DPT/OPT/OPG
When were radiographs first used in dentistry and what for?
- 1896 for decay and periapical pathology
why are radiographs used despite the fact that it is dangerous / ionizing radiation?
- diagnostic effects> adverse effects of x-rays
What is an atom? what is it made up of?
- atoms are building blocks of life
- consist of internal nucleus containing protons and neutrons, surrounded by a shell of electrons
why does an atom have no overall charge?
- protons: positive
- neutrons: neutral
- electrons: negative
no overall charge because NO. protons = NO. electrons
Describe the nature of electrons within energy shells, name the shells and how many electrons they contain.
- electrons sit in shells surrounding the nucleus
- shell names: k, L, M
- K= 2, L = 8, M=18
How can an electron be removed from an atom?
- Energy is required to overcome the binding energy, binding energy being the energy caused by attraction of negative electrons to positive protons
what is atomic number, atomic mass number and neutrons number?
- atomic: protons
- neutron: neutrons
- Mass: protons + neutrons
what are isotopes?
- Atoms with the same number of protons but different number of neutrons
what are radioisotopes?
- isotopes with unstable nuclei which undergo radioactive disintegration - atoms splits into smaller, more stable ones
- this changes the atoms from one substance to another
what is an ion?
- charged atom caused by loss or gain of electron/ becomes ionised
- positive ion: lost electrons
- negative ion: gained electrons
What are gamma rays?
- part of electromagnetic spectrum,
- no charge, mass or size
- travels very fast
- can penetrate through tissue and can cause damage due to ionization
Why is ionization a problem? gives an example of a condition caused by ionization
- 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
how does ionizing radiation cause damage to cells?
- 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
how does a basic circuit work?
- current passes along a wire through vibration of electrons
- the electrons pass from negative end (anode) to positive end (cathode)
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?
- electricity is converted to x-ray
- not efficient because most of the conversion of energy produces heat
