Principles of Radiography Flashcards
When is using Radiography appropriate?
Excellent for imaging bone and gas
Good for soft tissue
Good large scale
Gross structural
Limitations of radiography
Radiation risk
Need for restraint
Can’t see internal architecture very well
Still image
2D images
ALARP meaning
As Low As Reasonably Practicable
* Dose
* Personnel
* Times
* Distance
* Shielding
How does bone appear?
Bright/white
Radiopaque
How does fat appear?
Dark grey
Soft tissue opacity
How does gas appear?
Black
Radiolucent
How does soft tissue appear?
Grey
Soft tissue opacity
Radiopaque
○ Most x-rays are absorbed and few penetrate through to image-receptor
○ Appears white
○ E.g. metal and bone
Radiolucent
○ Few x-rays are absorbed, most penetrate through to image-receptor
○ Appears black
○ E.g. gas
○ Radiopaque
Which side of the image is cranial?
Left
Which side of the image is caudal?
Right
Most important safety aspects
Never place your hand in the primary beam
Never enter controlled area without PPE
Use vertical beam where possible
Avoid manual restraint
Properties of X-rays
- Short wavelength
- High Energy
- Transverse wave
- Requires high voltage to produce X-Rays
- Travel in a straight line
- No charge
- Can lead to ionisation
○ Damaging to living tissue - Can cause some substances to fluoresce
- Penetrate all matter to some degree
Production of X-rays
Cathode generates stream of electrons
Electrons hit atoms and result in X-rays being released
Quality
Penetrating power of beam
Intensity
Amount of radiation in beam
What does increased kV do?
Increased quality and intensity
* Increased electron acceleration
* Increased energy of electrons
* More x-rays produced
* Increased penetrating power
* More radiation in beam
What does increased mA do?
Increased quality only
* Increased tube current
* More electrons produced
* More x-rays produced
* Energy is unchanged
* Increased penetrating power
mAs
Measure of number of x-rays produced
kV
Acceleration of electrons
Pink Camels Collect Extra Large Apples
Positioning
Centring
Collimation
Exposure
Labelling
Artefacts
Positioning
- Part of interest close to image receptor as possible
- Part of interest parallel to image receptor
○ If incorrectly positioned, can distort image
Centring
Centre primary beam over area of interest
Collimation
- Collimation reduces production of scattered radiation
- Collimate beam to minimum size necessary
Exposure
Use correct exposure factors
under/over exposure will affect image
Labelling
- Always expose side marker
- Patient details are entered into PC software
- Lying in right lateral recumbency = R marker
Artefacts
- Appearances on image that do not correspond to structure of patient
- Check there is nothing that could cause artefact
○ Sandbags
○ Foam wedges
○ Drip lines
○ Collars
What does an underexposed radiograph look like?
Grainy
Quantum mottle
