Contrast media

1. Contrast MediaContrast Media

2. 22
Aims of this session Aims of this session
Why contrast agents are used Why contrast agents are used
What are the desirable features of a contrast agent What are the desirable features of a contrast agent
Types of contrast agents used in clinical settings Types of contrast agents used in clinical settings
Methods of administrating contrast agents Methods of administrating contrast agents
Examples of examinations utilising contrast agents Examples of examinations utilising contrast agents
Problems/issues associated with administrating Problems/issues associated with administrating
contrast agents contrast agents

3. 33
ContrastContrast
The difference in optical density The difference in optical density
between different parts of an image between different parts of an image
on a radiograph. It is a reflection of on a radiograph. It is a reflection of
the different absorption coefficients the different absorption coefficients
and bulk of different regions of the and bulk of different regions of the
part being radiographed part being radiographed

4. Contrast Media
It is a chemical substance of very high or
very low atomic number or weight, there
for it increase or decrease the density of
the organ under examination.

5. UNIT VII 5
“Contrast Media"
–substance placed
in the body to
provide added
contrast when
subject contrast is
low
–increases the
radiographic
contrast between
the area
containing the CM
& areas not
containing CM
Without
CM
With
CM

6. 66
Contrast MediaContrast Media
A substance which when introduced A substance which when introduced
into the body will increase the into the body will increase the
radiographic contrast in an area radiographic contrast in an area
where it was absent or low before. where it was absent or low before.

7. 77
Brief HistoryBrief History
1897 - First reported GI contrast study performed - 1897 - First reported GI contrast study performed -
Bismuth - TOXIC! Bismuth - TOXIC!
1910 - Barium Sulphate used (safer) 1910 - Barium Sulphate used (safer)
1920’s - Sodium Iodide used to treat syphilis. 1920’s - Sodium Iodide used to treat syphilis.
Iodine was found to be radio opaque to x-rays. Iodine was found to be radio opaque to x-rays.
Bases of all modern contrast agents. Bases of all modern contrast agents.
1927 - First reported IVU with iodised organic salts 1927 - First reported IVU with iodised organic salts
(Uroselectan)(Uroselectan)

8. 88
Requirements of a Contrast Agent (1)Requirements of a Contrast Agent (1)
Easy to administer
No toxicity
Stable compound. – Will not dissociate into
toxic ions
When injected the media concentrates in
area(s) required
The agent’s physical features allow the organ
to be properly demonstrated e
- even barium coating of the stomach in the
presence of an acid environment.


9. 99
Requirements of a contrast agent (2)Requirements of a contrast agent (2)
The agent should have rapid elimination.
The agent should not be carcinogenic.
The agent should have a viscosity
appropriate to the patient when
introduced.
The agent should cause minimal distress
to the patient when introduced.
The agent should be cost-effective.

10. 1010
Methods of administrationMethods of administration
Orally.
Rectally.
Intra- venously – (injection /
infusion).
Mechanically – Filling of a body
cavity or potential space.
Intra-muscularly.


11. 1111
Examples of areas where contrast Examples of areas where contrast
agents are usedagents are used

Arteriography
Angiography (DSA) – Cardiology
Venography (replaced by ultrasound-
Doppler)
IVU
Fluoroscopy – Alimentary tract,
hyserosalpingography, sialography,
Computerised Tomography (CT)
Magnetic Resonance Imaging (MRI)
Ultrasound – Liver, kidney
Myelography (replaced by MRI)
Arthrography – Knee joints.


12. Contrast Media
C.M
Negative
Air & its constitution
Positive
Iodine compound
Bso4
GIT
Water solublePowderOily

13. 1313
Types of contrast mediaTypes of contrast media
Negative Contrast Agents Negative Contrast Agents
- Air - Air
- CO- CO
2 2
- O- O
2 2

14. 1414
How do negative contrast agents How do negative contrast agents
perform?perform?
The negative contrast agents
reduce the atomic number of the
area to be demonstrated.
 These types of contrast media
will have little attenuation of the
x-ray beam.

15. 1515
Positive Contrast Agents Positive Contrast Agents
Barium based Barium based
Iodine based agents Iodine based agents
–Water soluble (Niopam) Water soluble (Niopam)
–Non soluble (Lipiodol, Myodol) Non soluble (Lipiodol, Myodol)




The positive contrast agents increase the atomic number
of the area to be demonstrated in relation to the
surrounding tissue.

16. •Powder contrast in a form of tablets e.g.
Biloptin, Cistobil.
•Oily contrast e.g. myodil, dinosil & lipidol.
•Water soluble ( addition of sugar).

18. .
Ionic e.g. urografine, urovideo, uromiro,
conray, hexbric & angoigrafine.
Non ionic e.g. Amipaque, omnipaque,
ultravist & isovist.
Note:- all nonionic C.M. are more safety
than ionic one.

19. •Water soluble C.M. found in different
concentration per ml so you must
check it carefully to calculate the dose.

20. Contraindications Iodine
(DO NOT USE)
hypersensitivity to iodine
heart or renal failure
liver disease

21. 2121
Double contrast agentsDouble contrast agents
Incorporates the use of both positive & Incorporates the use of both positive &
negative contrast media. negative contrast media.
eg during a double contrast Barium enema eg during a double contrast Barium enema
examination. examination.

CoCo
22
+ BaSo + BaSo
44
= Double Contrast = Double Contrast

22. 2222
Why use Barium Sulphate?Why use Barium Sulphate?
It has a high atomic It has a high atomic
number (Z=56) number (Z=56)
Non-toxic Non-toxic
Relatively cheap Relatively cheap
InertInert

23. 2323
Pharmacological agentsPharmacological agents
Buscopan Buscopan
Glucagon Glucagon
Maxalon Maxalon


Why are they given?Why are they given?

24. 2424
Pharmacological agentsPharmacological agents
Buscopan (20mg iv) & Glucagon (0.3mg iv) Buscopan (20mg iv) & Glucagon (0.3mg iv)
both relax smooth muscle (Glucagon more both relax smooth muscle (Glucagon more
potent & can be used on patients with potent & can be used on patients with
glaucoma & cardiovascular disease). glaucoma & cardiovascular disease).
Useful in barium enema examinations.Useful in barium enema examinations.

Maxalon (20mg iv/oral) increases gastric Maxalon (20mg iv/oral) increases gastric
peristalsis peristalsis
(useful in (useful in follow through examinations) follow through examinations)

25. 2525
Iodine based contrast agents Iodine based contrast agents
(1)(1)
Approximately 90% of all contrast media
used in x-ray imaging are loosely termed
intravascular or general contrast media.
The physical properties of the iodine based
contrast media include the ions or particles
associated with the chemical breakdown of
the contrast media when it enters a
solution.

26. 2626
Iodine based contrast agents Iodine based contrast agents
(2)(2)
The chemical composition of ionic & non-ionic
contrast media contains iodine.
On its own, iodine is unsuitable as a contrast
agent as it toxic!
The answer is to attach iodine to a “carrier”
molecule
Achieved by basing the molecule on the
benzene ring & replacing the carbon atoms at
set points with iodine to produce tri-iodinated
benzoic rings

27. 2727
Ionic Contrast AgentsIonic Contrast Agents
An ionic compound dissociates
(dissolves) into charged particles
when it enters a solution (ie blood)
Ionic media breakdown into cations
(+ive charged particles) & anions (-ive
charged particles)


28. 2828
Ionic Contrast AgentsIonic Contrast Agents
An ionic contrast agent has approximately
five times the osmolarity of human plasma
(hyperosmolar)
The iodine atoms provide the attenuation
properties
The additional chemical groups determine the
properties of the contrast agent, ie solubility,
toxicity, viscosity, osmolarity.
–

29. 2929
OsmolarityOsmolarity
The osmolarity of a solution is the measurement of The osmolarity of a solution is the measurement of
the number of molecules & particles in a solution the number of molecules & particles in a solution
per kilogram of water. per kilogram of water.

30. 3030
ViscosityViscosity
Viscosity describes the
thickness or resistance to
flow of a contrast agent
The thickness of the contrast
agent is related to the
concentration, the size of the
molecules in a specific
contrast agent & the
temperature of the contrast
agent.
The viscosity affects the rate
that the contrast media can
be injected.


Q:Why are power injection (Medrad) devices fitted with warming pads? Q:Why are power injection (Medrad) devices fitted with warming pads?

31. 3131
Medrad - Power InjectorMedrad - Power Injector
Warming pad Keeps the viscosity LOW.

32. 3232
Non-Ionic contrast mediaNon-Ionic contrast media
Often referred to as “low osmolar” Often referred to as “low osmolar”
Non-ionic contrast media do not dissolve into
charged particles when it enters a solution
For every three iodine molecules in a non-
ionic solution, one neutral molecule is
produced
Non-ionic contrast media are referred to as
3:1 compounds

33. Non-ionic contrast agents are therefore far
safer than ionic contrast agents
More expensive (++)
Non-ionic contrast agents substitute the Non-ionic contrast agents substitute the
sodium & meg side chains with non-sodium & meg side chains with non-
ionising radicals (NIRionising radicals (NIR). ).

34. 3434
Gastrograffin & GastromiroGastrograffin & Gastromiro

Water soluble iodine based contrast agents Water soluble iodine based contrast agents
Designed especially for G.I. use Designed especially for G.I. use
Characteristic aniseed taste. Characteristic aniseed taste.
Particularly useful in neonates & paediatrics Particularly useful in neonates & paediatrics
Isotonic at iodine concentrations (Gastromiro). Isotonic at iodine concentrations (Gastromiro).
–Gastrograffin = (370 mg mlGastrograffin = (370 mg ml
-1-1
) )
–Gastromiro = (300 mg mlGastromiro = (300 mg ml
-1-1
) )
Satisfactory for good images of the bowel Satisfactory for good images of the bowel
Recommended for use where there is a Recommended for use where there is a
suspected leakage into pleural or peritoneal suspected leakage into pleural or peritoneal
cavities. cavities.
Also useful in CT to distinguish bowel from other Also useful in CT to distinguish bowel from other
structures(15ml in 1 litre) structures(15ml in 1 litre)




35. 3535
Recent development of contrast Recent development of contrast
agents (1)agents (1)
Current contrast agents reaching the critical Current contrast agents reaching the critical
iso-osmolarity stage within the human body iso-osmolarity stage within the human body
Increased hydrophilicity due to an Increased hydrophilicity due to an
increased number of hydroxyl groups increased number of hydroxyl groups
provides a high affinity for water and provides a high affinity for water and
shelters the toxic iodine atoms from the shelters the toxic iodine atoms from the
human body. human body.
Particularly useful for paediatrics & hyper-Particularly useful for paediatrics & hyper-
sensitive patients.sensitive patients.

36. 3636
Recent development of contrast Recent development of contrast
agents(2)agents(2)
MRI MRI
Gadolinium is a rare earth metal “heavy Gadolinium is a rare earth metal “heavy
metal” metal”
Gadolinium is chelated to DTPA Gadolinium is chelated to DTPA
(Magnevist) (Magnevist)
By binding DTPA to the Gadolinium sites, By binding DTPA to the Gadolinium sites,
only one “free” gadolinium site is only one “free” gadolinium site is
available to attach to water molecules available to attach to water molecules
Gadolinium chelates are of small Gadolinium chelates are of small
molecular weight molecular weight
Diffuse freely & excreted by kidneys Diffuse freely & excreted by kidneys
Typical adult dose = 0.2ml/kg (20ml max) Typical adult dose = 0.2ml/kg (20ml max)

37. 3737
MRI – Example imagesMRI – Example images
MRI (Gd-DTPA) – Hepatoblastoma MRI (Gd- DTPA) Metastasis