Contrast Media

Question 1

How does contrast media work?

Answer 1

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

Question 2

What are the different types of contrast media?

Answer 2

Negative contrast media: dark
Air CO2 O2

Positive contrast media: bright
Iodine based
Barium based
Gadolinium based

Question 3

How does negative contrast media preform?

Answer 3

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

Question 4

How does positive contrast media perform?

Answer 4

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

Question 5

Examples of positive contrast media:

Answer 5

Barium based - baritop

Gadolinium based - gadovist

Iodine based
- water soluble -niopam,omnipaque, visipaque

Non soluble - lipoidal- seldom used

Question 6

Why use barium sulphate?

Answer 6

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

Question 7

Exposure factors with Barium:

Answer 7

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

Question 8

Problems with ionic CM?

Answer 8

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

Question 9

What are the two categories contrast media is divided into iodine?

Answer 9

High osmolar contrast media

Low osmolar contrast media

Question 10

What is osmolality?

Answer 10

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

Question 11

Three types of osmolality?

Answer 11

Hypotonic - gains + swells

Hypertonic- loses - shrinks

Isotonic - same

Question 12

Iodine best compounds – ionic plus non-ionic?

Answer 12

Both ionic and nonionic CM contain iodine

Iodine - unstable - on its own

Attach iodine to carrier molecule

Question 13

Non-ionic contrast – LOCM?

Answer 13

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

Question 14

Advantages and disadvantages of ionic and ionic media?

Answer 14

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

Question 15

What is the ideal contrast medium?

Answer 15

Ease of administration
Non-toxic
Stable
Concentrates in area of interest
Non-carcinogenic
Appropriate viscosity
Easy for patient to tolerate
Cost effective

Question 16

Ideal intravenous contrast media:

Answer 16

Water soluble
Storage stability
Non-antigenic
Optimum viscosity/density
Ease of excretion post exam
ISO-osmolality
Non toxic
Affordable 

Question 17

Iodine contrast media exposure factors?

Answer 17

Low atomic no.
Maximum contrast is achieved by using a lower energy setting -70Kv

(High energy will reduce contrast)

Question 18

Methods of Administration of contrast media?

Answer 18

Orally
Rectally
IV - injection/infusion
(Aciticubital fossa) - risk extravasion
Mechanically filling body cavity or potential space

Question 19

Areas where contrast media is used?

Answer 19

CTIVU - urinary
Fluoroscopy- GI Tract
Arthrography - MRI
HSG
Urethrogram
CT
MRI
US
RNI

Question 20

Gastrografin and gastromiro:

Answer 20

Water soluble iodine based CM
Especially for GI
Good images of the bowel
Used when suspected leak into peritoneal or pleural space

Question 21

What are iodised oils?

Answer 21

In frequently used in radiography



Question 22

Carb X granules what are they and what do they do?

Answer 22

Sherbert like granules

On contact with patients mouth form carbon dioxide from making a negative contrast medium

Used in barium meals

Question 23

 what is pharmacological media?

Answer 23

Buscopan and glucagon - both relax smooth muscle

Useful in large bowel examinations

Maxalon increases gastric peristalsis- follow through

Question 24

Adverse reactions to contrast media?

Answer 24

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

Question 25

Specific organs affected by adverse reaction to CM:

Answer 25

Cardiovascular toxicity

Nephrologixal toxicity

Neurotoxicity

Question 26

Cardiovascular toxicity – symptoms/signs

Answer 26

Pain

Thrombus formation

Platelet aggression

Osmotic effect

Fluid shifts

Ventricular arrhythmia

Question 27

Nephrological toxicity – signs and symptoms
Predisposing conditions

Answer 27

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

Question 28

EGFR – kidney disease

Question 29

Neurotoxicity?

Answer 29

Related to osmolality

More likely in patients with brain tumours and brain abscesses

Question 30

How do we protect patients from adverse reactions?

Answer 30

Indentify high risk patients Questionnaire:
Minimises potential risk and allows for any pro-prolapse measures

Question 31

At risk groups for adverse reactions?

Answer 31

Age
Allergies
Anxiety
Asthma
Cardiac arrest
Dehydration
Diabetes