Contrast Media Flashcards
How does contrast media work?
Soft tissue provides little difference in attenuation by the x-ray beam but introducing contrast where it did not previously exist we improve our visualisation of soft tissue structures
What are the different types of contrast media?
Negative contrast media: dark
Air CO2 O2
Positive contrast media: bright
Iodine based
Barium based
Gadolinium based
How does negative contrast media preform?
The negative contrast media reduces the atomic number of the area to be demonstrated
these types of contrast media will reduce attenuation of the extra beam
How does positive contrast media perform?
The positive contrast media increases atomic number of the area to be demonstrated in relation to the surrounding tissue
x-rays considerably attenuated by the contrast media
Examples of positive contrast media:
Barium based - baritop
Gadolinium based - gadovist
Iodine based
- water soluble -niopam,omnipaque, visipaque
Non soluble - lipoidal- seldom used
Why use barium sulphate?
High anatomical no.
Relatively cheap
Non toxic
Inert - sulphate makes it non-toxic
Excellent coating properties for GI
Defoaming agent - no bubbles
Dispersing agent so even distribution of particles
Exposure factors with Barium:
High energy- above 100kv
Compton effect predominates
Bowel more obvious
Lower contrast between Ba and soft tissues/bone
Higher contrast between air and soft tissue/barium
Problems with ionic CM?
The body is far more sensitive to ionic CM so more allergic reactions occur
Ionic contrast media still In regular use is gastrografin - but given orally in certain situations
What are the two categories contrast media is divided into iodine?
High osmolar contrast media
Low osmolar contrast media
What is osmolality?
The osmolality of a solution is the measurement of the osmotic pressure relative to pure water
The higher the iodine the higher the osmolality
Any solution that has an osmolality over blood plasma is said to be hyperosmolar

Non-ionic + ionic CM are hyperosmolar
Three types of osmolality?
Hypotonic - gains + swells
Hypertonic- loses - shrinks
Isotonic - same
Iodine best compounds – ionic plus non-ionic?
Both ionic and nonionic CM contain iodine
Iodine - unstable - on its own
Attach iodine to carrier molecule
Non-ionic contrast – LOCM?
Manufacturers needed to make a contrast media which was as near to the osmolality of blood plasma as possible
Non ionic LOCM:
Visipaque
Omnipaque
Lomeron
Optiray
Advantages and disadvantages of ionic and ionic media?
Ionic media –
Dissociate in solution
Less expensive
can be tolerated in body cavities
Non-ionic media:
Closer to body homeostasis
More expensive
Better tolerated by patients
Can be used in the circulatory system
Reduced no. Of side effects
Stimulates less histamine release
Decreases vasodilation
Reduced effect on blood brain barrier
What is the ideal contrast medium?
Ease of administration
Non-toxic
Stable
Concentrates in area of interest
Non-carcinogenic
Appropriate viscosity
Easy for patient to tolerate
Cost effective
Ideal intravenous contrast media:
Water soluble
Storage stability
Non-antigenic
Optimum viscosity/density
Ease of excretion post exam
ISO-osmolality
Non toxic
Affordable 
Iodine contrast media exposure factors?
Low atomic no.
Maximum contrast is achieved by using a lower energy setting -70Kv
(High energy will reduce contrast)
Methods of Administration of contrast media?
Orally
Rectally
IV - injection/infusion
(Aciticubital fossa) - risk extravasion
Mechanically filling body cavity or potential space
Areas where contrast media is used?
CTIVU - urinary
Fluoroscopy- GI Tract
Arthrography - MRI
HSG
Urethrogram
CT
MRI
US
RNI
Gastrografin and gastromiro:
Water soluble iodine based CM
Especially for GI
Good images of the bowel
Used when suspected leak into peritoneal or pleural space
What are iodised oils?
In frequently used in radiography

Carb X granules what are they and what do they do?
Sherbert like granules
On contact with patients mouth form carbon dioxide from making a negative contrast medium
Used in barium meals
 what is pharmacological media?
Buscopan and glucagon - both relax smooth muscle
Useful in large bowel examinations
Maxalon increases gastric peristalsis- follow through
Adverse reactions to contrast media?
Idiosyncratic anaphylactic reactions:
Not dose dependant
Anaphylactic
Unpredictable
Fatal 1 in 170000
Non-idiosyncratic reactions:
Chemotoxic & hypersmolar
Vasovagal
Minimised by used of LOCM
predictable reactions
Dose dependant
Specific organs affected by adverse reaction to CM:
Cardiovascular toxicity
Nephrologixal toxicity
Neurotoxicity
Cardiovascular toxicity – symptoms/signs
Pain
Thrombus formation
Platelet aggression
Osmotic effect
Fluid shifts
Ventricular arrhythmia
Nephrological toxicity – signs and symptoms
Predisposing conditions
Renal output leading to renal impairment – increased creatinine
Predisposing conditions:
Pre-existing kidney disease
Diabetes melitis
Multiple myeloma
Dehydration
Large volume of contrast administered
Patient age
EGFR – kidney disease
Neurotoxicity?
Related to osmolality
More likely in patients with brain tumours and brain abscesses
How do we protect patients from adverse reactions?
Indentify high risk patients Questionnaire:
Minimises potential risk and allows for any pro-prolapse measures
At risk groups for adverse reactions?
Age
Allergies
Anxiety
Asthma
Cardiac arrest
Dehydration
Diabetes
