13.1, 2 Radiology and Contrast Media Flashcards
What is a contrast media?
A constrast medium is:
a substance put into body
improve visibility of internal structures during radiography
What are positive and negative contrast mediums? Give examples of both.
Positive: appear more radiopaque (white) than surrounding tissues (high atomic no. = barium, iodine, gadolinium)
Negative: appear more radiolucent (black) (gases of low density = air, oxygen, water, CO2)
How is contrast media administered?
Oral, IV, Rectal, IA, fill a space or cavity
What are the side effects of using contrast media?
- reactions due to osmolality
- endothelial damage
- thrombosis and thrombophlebitis
- vasodilation
- vascular pain
What types of modalities can contrast media be used in?
- Fluoroscopy
- CT
- MRI
- Arteriograms
- US
What properties make an ideal contrast media substance?
- low osmolality and viscosity
- high water solubility
- biologically inert
- safe
- heat and chemically stable
- cost effective
What is the difference between idiosyncratic and non-idiosyncratic reactions?
idiosyncratic - within 20 mins
non-idiosyncratic - after 30 mins
What are the CT/MRI imaging planes?
axial (transverse), coronal, sagittal, oblique (diagonal)
How can the 2 biological effects of radiation exposure be classified?
- Deterministic: threshold of no effect and then a steep rise after the threshold
- Stochastic: risk is directly proportional to dose
How do we measure radiation?
READ
R - radioactivity = amt of ionising radiation relesed
E - expose = amt travelling through air
A - absorbed dose
D - dose equiv = combines absorbed and medical effects
What does ALARA stand for?
As Low As Reasonably Achievable
Outline some MRI contraindications
- cardiac pacemaker
- implanted/external medical pump
- cochlear implant
- catheter with metallic components
