Contrast Flashcards
what is radiolucent
when x-rays can pass through
what is radio-opaque
when x-rays pass through at a lower extent
what property is similar for soft tissues
absorption
what absorbs more bone or soft tissue
bone
what are the two types of contrast
+ and -
describe negative contrast
- not used
- radiolucent (x-rays pass through)
- less dense than soft tissues
- absorbs less radiation than ST
- structure becomes dark
describe positive contrast
- absorbs more x-rays than ST
- more dense than ST
- radio-opaque
- structures are white
- used in RT
what contrast is barium sulphate
it is a positive agent which is found as a suspension used for the GI tract
what happens if the blood brain barrier is crossed
increased chance of substances passing through. the active section of the tumour has a high metabolic rate which has a faster uptake of contrast
what type of contrast is iodine based agents
positive
describe iodine based agents
- liquid form
- used in GI tract, kidneys and head and neck
- can be ingested, injected or used in the body cavities
- used for localisation
are ionic agents used in RT
no they have a higher osmolar contrast which dissociate into positive and negative ions
what are iso-osmolar agents
non ionic, which have no osmosis occur due to the concentration being relative to plasma.
an example of iso-osmolar
omni-opaque 300
describe non ionic agents
they contain a side chain which dissolves in water. It is a low osmolar media so the osmolarity side effects are reduced
what is the criteria for contrast
- little/no side effects
- concentrated in the area of interest
- easily administered
- stable
- appropriate storage
- appropriate viscosity
- non toxic/carcinogenic
- rapidly eliminated by the body
what are the risk factors
- extremities of age
- previous reactions
- allergies or asthma
- cardiovascular disease
- diabetes
- dehydration
- anxiety
- blood disorders
what are the minor complications (no risk)
- anxiety
- local pain
- nausea
- flushing
- uritiaria or itching
what are the intermediate complications (medical attention)
- more severe minor complications
- mild bronchospasm
- mild hypotension
what are the severe complications (urgent)
- severe minor complications
- respiratory collapse
- cardiovascular collapse
- convulsions
- unconsciousness
- cardiac arrest
- laryngeal oedema
- cardiac dysrhythmia
what are the pre cautions
- no previous reaction
- emergency drugs close by
- monitor patient closely
- must stay within the department for 30 minutes afterwards
