Radiography/radiology Flashcards
Pink Camels Collect Extra Large Apples
P=Positioning (Position part of interest as close to the image receptor, must be parallel NOT oblique or else image will distort. No movement or superimposition)
C= Centering (centre the primary beam over the area of interest, esp in LA)
C= Collimation (collimate beam size to minimum necessary to see desired area to reduce scattered radiation)
E= Exposure (use the right exposure factors
L= Labelling (patient details and date in software, area radiographed DV, VD, RLat, Llat etc. Always expose side marker (R/L)
A= Artefacts (Check there is nothing thaty could cause artefact)
kV
affects the quality and intensity
mA
affects the intensity only
- if increased, tube current increases, number of electrons increases
- therefore, there is a greater number of x-rays produced.
Energy of the xrays is unchanged
what substance appears black on radiograph
Air
Appears grey on radiograph
fat (darkest grey)
Water (Lighter grey in comparison to fat)
what structures appear white on radiograph
Bone
Metal (more vibrant white in comparison to bone)
Why do different structures show up as different colours on a radiograph
different tissues absorb differetn amounts of radiation
Fat absorbes less than bone
what happens when you increase kV
5
- the overall amount of radiation emerging from the patient and reduces the difference between different structures
- increased electron acceleration
- increased energy of electrons
- greater number of x rays produced
- xrays have increased energy = increased penetrating power
What happens when you decrease the kV
decreases the amount of exposure of the image receptor and increases the difference between different structures
What happens when you increas mAs
Increase the overall amount of radiation emerging from the pation
increases plate exposure
What happens when you increas mAs
Increase the overall amount of radiation emerging from the pation
increases plate exposure
What happens when you decrease mAs
Decreases the overall amount of radiation emerging from the patient
decrease plate exposure
What does it mean if you see a blackk area on a radiograph
the X-rays ahve penetrated through the body and have not been stopped
white means X-rays have been absorbed by body
What is the term for taking 2 images at right angles to eachother
orthogonal views
necessary bc rads are 2D and patient is 3D, 2 views gives full picture
What are X-rays?
a form of electromagnetic radiation
they have a high energy and a short wavelength
can lead to ionisation (damaging to living tissues)
How are X-rays produced
5
- the interaction of electrons with an atom
- the cathode (-ve) in an X-ray tube generates a stream of electrons
- these hit and interact with the atoms within the target area of the anode(+), resulting in the release of X-rays
- the number of electrons generated at the cathode is determined by the mA and Exposure time
- the energy of the electrons striking the anode is determined by the kV applied
Properties of the X-ray beam
2
QUALITY: the penetrating power of the beam
INTENSITY: amount of radiation in the beam
effect of exposure time
increasing time of exposure increases number of xrays
mA x sec = mAs
Source of image-receptor distance (SID)
- the closer to the x-ray tube the image-receptor is, the more concentrated the xray beam will be and vice versa
- the exposure vaires according to the inverse square law
How do you reduce scattered radiation
- good collimation
- use of a low kV
- use of a radiographic grid if necessary
What should a good radiograoh show
3
- accurate portrayal
- easy perception (sharp shadows, wide range of shades of grey)
- no misleading artefacts
Where do you look on a radiograph to assess if you have axial rotation in a thoracic view
the dorsocaudal ribheads (must overlie eachother)
NOT where the rib bodies lie
