Principles of Radiography Flashcards
What is teleradiology?
Sharing images with other radiologists and physicians.
When are radiographs not useful and why?
When fluid and soft tissue structures present - they look the same/are the same radiographic density.
Name 8 Roentgen signs?
- Number
- Location
- Size
- Margination
- Radiopacity
- Internal architecture
- Function
If an animal has fluid in its thorax and is struggling to breath, what position do we not want them in?
Sternal recumbency
Name three types of restraint methods for radiography?
- sedation
- general anaesthesia
- positioning aids.
Should animals be manually restrained for radiography?
No, except in exceptional circumstances!
When would sedation be viable?
For thoracic and abdominal radiography and maybe some MSK studies where GA would be undesirable.
What two things are important in sedated, sick patients?
Oxygenation and careful monitoring.
Name three scenarios where general anaesthesia would be commonly used?
- Most MSK studies e.g. fractures
- Good quality, inspiratory thoracic radiographs
- Most contrast studies (not needed for oral barium
If radiographing the spine, why is it better to use GA?
Because the patient needs to be completely still.
How can movement blue be minimised?
Correct use of the machine and equipment.
What is needed to reduce movement blur and why?
Movement blur is related to time (MAs) therefore need to increase the MAs and reduce the time.
What are the two types of movement blur?
Voluntary e.g. muscle and limb movement in a conscious animal.
Involuntary movement e.g. breathing.
How will most large animals be radiographed?
Standing with sedation.
Name a body area in large animals that will probably require general anaesthesia?
The pelvis.
Name three things included in a good radiograph?
- accurate portrayal
- easy perception e.g. sharp shadows and a wide range of shades of grey
- no misleading artefacts.
To maintain consistent results with radiography, what is needed?
Standardisation of the technique.
What are the standard views used for radiography?
2 orthogonal views at least (right angles to each other)
What are the routine radiographic views for the thorax?
RLR (Right laterla recumbency) and DV.
What views would be used for a lung metastasis screen?
RLR, LLR, and DV or VD
What views would be used specifically for lung pathology?
RLR (+LRL) and VD
Which views would be used for the abdomen?
RLR or LLR and VD.
Which views would be used for the pelvis or the spine?
RLR or LRL and VD
Which views would be used for the limbs?
Mediolateral and CrCd/ CdCr/ DP/PD
Which views would be used for the skull?
RLR or LLR and DV
What are the 4 common joints to be radiographed in the horse?
- fetlock
- hock
- stifle
- carpus
Would you only do two orthogonal views in the horse and why?
No, you would do more than two orthogonal views because the horse is so much bigger.
How many views would you standardly do in the equine limb?
4
What would these 4 views be in the horse distal limb?
- lateromedial
- DP/PD
- 2 x 4 degree oblique angle
What are the two common oblique views taken in horses?
Dorso-Lateral-Plantaro-Medial-Oblique (DLPMO)
Dorso-Medial-Plantaro-Lateral -Oblique (DMPLO)
What do we need the animal to do before an abdominal radiograph?
Try and starve the animal 24 hours before an abdominal radiograph and allow to urinate/ defecate before imaging.
For thorax and limbs, how much pre-starvation will the animal require?
12 hours is fine, but for abdomen, 24 hours is preferential.
What do we need to make sure in terms of the area of interest and why?
Position the area of interest as close to the cassette as possible. want to minimise distortion and magnification.
What angle does the part of interest need to be to the cassette?
Parallel to the cassette.
What happens to the x-ray bean as it leaves the x-ray tube?
It diverges and magnification occurs.
What do we need in order to minimise the amount of magnification?
Minimum object-film distance (OFD), maximum film-object distance (FOD).
What two reasons do we get object distortion?
If the site of interest is not parallel to the beam.
if the site of interest is not central in the beam.
What can be the 3 results of object distortion?
Object elongation, foreshortening, out of position
Where does the centre of the beam have to be?
In the middle of the casette and in the middle of the area of interest.
Why is it always best to use standard positioning first?
Because this enables comparisons e.g. textbooks.
Where do we look to determine if there is axial rotation?
The dorsocaudal ribcage.
What should we see if there is no axial rotation and good positioning?
The dorsocaudal rib cage should be superimposed.
Where do we want the centre beam and why?
To be centred over the area of interest because the X-ray will be vertical in the centre, if not, this will be misleading.
Name two disadvantages of scatter?
It contributes to general radio-opacity and is a health hazard.
Why is collimation important?
Because it reduces scatter.
How should we collimate joints?
Should include 1/3 of the adjacent bone.
For long bones, how should we collimate?
We should collimate the whole of the long bone, including two joints - one above and one below.
When we assess collimation, what are we looking for?
we are looking for four unexposed borders. This tells us that the radiation has not gone off the side of the plate.
How is collimation described?
25% for each border e.g. if all 4 borders are unexposed, this is 100% collimated.
Why is digital imaging an issue when assessing collimation?
Because it is not possible to judge collimation when there is an application of automatic black borders on digital imaging.
What is the next stage for assessing collimation?
Decide the % and then describe how closely correlated to the image e.g. close or wide.
What is the rule about detecting exposure from the viasual appraisal of a digital image?
You cannot tell whether the image is under or over-exposed.
What do you need to avoid?
‘exposure creep’ where the exposure slowly creeps up.
What affects the NUMBER of x-rays produced?
Kv, Ma and time.
Which affects the PENETRATING power of the x-rays?
KV
If you have an under-exposed image, what do you need to do?
Increase Kv
How does the thickness of the animal influence the scatter of radiation?
The thicker the animal, the more radiation.
What is a grid?
It is alternating strips of lead and plastic which filter x-ray photons which are not travelling vertically/ in a forward direction.
When do you use grids?
In body regions thicker than 10-15cm
What determines how much scatter radiation is filtered?
the width and height of the strips
Which part of the beam is travelling vertically?
Only the centre of the beam
What do you need to make sure you do if you are using a grid and why?
Need to take into account the grid factor e.g. increase the MAs by 2-3x. This is because some of the primary beam will be absorbed by the grid.
Why do we only use a grid if it is going to be useful?
Because there needs to be increased MAs used which will decrease the image quality and more of a health and safety risk.
What are the three things that have to be set-up correctly when using a grid?
Has to be in the centre of the x-ray beam, has to be the correct way up, has to be the correct film-focal distance.
When do we want to take a thoracic radiograph?
At the time of inspiration.
Where does the diaphragm meet the spine?
T10-T11.
What labels should always be used on the image?
The patient and date should be in the system already. Should ALWAYS use side markers on the image.
Name three common artefacts seen on radiographs?
Sandbags
Troughs
Driplines
When should you take your radiograph of the thorax and why?
Expiratory pause because this is when the diaphragm is foward therefore will show the whole of the diaphragm.
