Principles of radiological interpretation Flashcards
What is radiographic conrast media?
Media that is administered to the patient and is either more radioopaque or radiolucent than the surrounding tissue.
What 5 things does contrast media provide?
- shape
- size
- position
- internal structure
- sometimes function
What appearance do negative contrasts have?
Radiolucent appearance –> low radiographic opacity e.g. air and gases
What appearance do positive contrasts have?
Radiopaque appearance e.g. barium, meglumine, iohexol, diatrozoate. This type of media has a high atomic number.
What is a downfallof contrast media?
Can have adverse effects.
What are the 7 properties of ideal contrast agents?
- differ from tissue under examination in terms of ability to absorb x-rays
- non-irritant, non-toxic
- accurately delineate the body part being examined
- persist for the duration of the study
- be totally eliminated afterwards
- be easily administered
- be cost effective.
What do you always need to do before taking a contrast radiograph?
Take a plain (survey) radiograph first.
What is another rule in terms of taking images when using contrast?
Need to take enough images!
1. need to take 4 images, one in each plane of the body e.g RLR, LLR, VD and DV
Is it worth taking another image after the contrast has left the animal?
Yes, because the contrast might be stuck in something that was previously missed.
where are negative contrast agents most commonly used?
In the bladder and GIT.
What is a double contrast study?
It is when a negative contrast agent is used with a positive contrast agent
what are the advantages of using negative contrast study?
It is cheap, quick and convenient.
It is also relatively safe.
What is a benefit of using double contrast study, what does it enable us to see?
Gives good margins.
What are three disadvantages of using negative contrast alone?
- poor mucosal detail if used alone
- air will be slowly eliminated from the body and therefore will confuse later studies.
- chance of air embolus in the blood - safer to use carbon dioxide as more soluble.
why is carbon dioxide safer to use?
Because it is more soluble therefore less likely to form an embolus.
What is an example when you would use barium sulphate studies?
GI contrast studies.
Name 5 advantages of using barium sulphate?
- low toxicity
- inert
- excellent MUCOSAL DETAIL
- may be therapeutic
- relatively cheap
How is barium sulphate administered?
As a suspension, paste, or mixed with food
What are the two disadvantages of using barium sulphate?
- careful with aspiration (do not administer under GA)
2. becomes quite an irritant if enters body cavities therefore need to be careful with suspected perforations!
Name 8 reasons for using a water soluble iodine preparation?
- myelography
- Cardiovascular system
- urinary tract
- joints
- salivary glands
- tear ducts
- fistulas/ sinuses
- GIT
What are the two types of water soluble iodine preparations?
- Ionic
2. Non-ionic
How is ionic administered?
Suitable for IV or direct administration (but NOT myelography) e.g. meglumine diatrozoate
How is non-ionic administered?
Suitable for myelography and any other use e.g. iohexol.
Which type of water soluble iodine preparations are recommended and why?
non-ionic as fewer side-effects.
Which type of water-soluble iodine preparation can be used for myelography?
Non-ionic
What is the third class of water-soluble iodine preparations and what is it used for?
Gastro-intestinal preparations used solely for GIT contrast studies.
What are the advantages of water-soluble iodine preparations (2)?
- very versatile and can be injected directly IV.
2. is rapidly absorbed if leaks into body cavity.
Name 5 disadvantages of using water-soluble iodine preparations?
- Hyperosmolar (ionic) –>might cause unpleasant side effects in conscious animals e.g. nausea and vomiting.
- Irritant if injected around the blood vessels (ionic)
- dose is weight related and iodine can be toxic if too high dose.
- IV administration is contra-indicated in animals with hypovolaemia, hypotension or cardiac/renal failure
- Might cause acute iodine-induced renal failure. although this is rare.
What is the advice before using water-soluble iodine preparations?
GA, use the non-ionic formulation, adequate hydration.
what is myelography?
This is contrast radiography of the spine and the subarachnoid space.
what is intravenous ureography and excretion urography?
contrast into veins and excreted by kidneys
cystography?
Contrast study of the bladder.
Urethrography?
This is a contrast study of the urethra
cardio-angiography?
This is a contrast study of the heart and the blood vessels.
Arthrography?
This is a contrast study of the joints.
Dacryocystography?
Lacrimal passages.
Pneumocystography?
Infusion of air into the bladder.
Double contrast cystography?
Infusion of positive contrast, followed by air into the bladder.
What imaging modality is commonly used instead of myelography?
MRI
What is commonly used instead of angiocardiography?
ultrasound.
What contrast study would give the best mucosal detail of the bladder?
Double contrast cystogram.
what are CT and MRI?
Cross-sectional imaging.
Name 3 benefits of CT and MRI?
- Avoids superimposition
- Superior to radiography for a lot of conditions
- They are very good for surgical planning of a disease e.g. oncology
Name 4 disadvantages of MRI and CT?
- Radiography and US might be more efficient
- Long periods of restraint required, especially in MRI
- cost
- availability.
Is MRI better for soft tissue or for bone?
Soft tissue
Name 7 examples where CT would be particularly useful?
- nasal cavities
- middle ear
- joints
- pharynx
- lungs
- thoracic and abdominal masses
- portosystemic shunts (angiography)
Name 4 examples where MRI would be particularly useful?
- nervous system
- middle ear
- soft tissue masses e.g. in the head
- some joints e.g. shoulder, stifle, muscles and tendons
Which is more appropriate for imaging the skull?
CT
What 7 things should be included on a radiography report?
- Sufficient to make someone else reading understand the radiograph you are talking about without it being pointed out.
- use roentgen terms to describe
- focus on important points
- also describe areas with no lesions toshow they have been thought about
- should put the abnormalities listed and prioritised according to significance
- differential diagnosis and likelihood
- further diagnostic tests necessary
How should you view an image?
In a dark room with a good quality screen size and image. High resolution LCD>
Which orientation should you use to view your images?
Standard orientation
What is border obliteration?
This is when the structures are of the same opacity and are in contact.
What is silhouette sign and border effecement?
The same as border obliteration.
What is more common in older animals?
Multiple diseases
What should you not use measurements for?
DO NOT base diagnosis on measurements alone!
What is a search error?
This is failure to examine the whole radiograph
e.g. overlooking absence of normal structure because found something that fits an answer. over-reliance on pattern recognition where you have seen something similar before.
distraction by dramatic abnormality.
What are judgement of analysis errors?
Over-reading or over-reading.
What are the 4 things that lead to under-reading?
- failure to recognise poor technique
- lack of knowledge
- commiting to a diagnosis before radiography
- interpretating a certain combination of signs as a specific diagnosis.
What 4 things lead to over-reading a radiography?
- misinterpret normal anatomy
- classification of incidental findings as significant
- mistaking artefacts for pathology
- faulty reasoning e.g. found a lesion, but incorrectly localised,
What are the three key things we are hoping for with radiography?
- narrow differential diagnosis
- find location of problem
- specific diagnosis.
