Upakar Paudel UCMS

1. Contrast Media and Its Types
Upakar Paudel
B.Sc.MIT 2nd Year
Roll no-6
UCMS Bhairahawa, Nepal

2. Introduction
• Contrast agents are the substances which possess an atomic no or
have an e- density which differs significantly from that of surrounding
structures & permits the visualization of the details of internal organs
that would not otherwise be demonstrable.
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3. History
• 1896, walter B. Cannon use radiopaque sustances.
• 1904, colloidal silver was used in retrograde urography.
• 1910, Krause use barium sulphate for visualisation of GIT.
• 1923, Osborne reported the opacification of UT after the injection of
10% NaI soln.
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4. History
• 1928, compound with no of pyridine rings containing iodine .
• 1952, first tri-iodinated compound (sodium acetrizoate) was
introduced.
• Until the early 1970s all CM were ionic compounds with osmolalities
of 1200-2000 mosmal/kg.
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5. History
• Ionic monomer:
1954, diatrizoate (urografin)
1962, iothalamate (conray)
1962 – 1972,
Metrizoate,Iodamide,Ioxithalamate,
Ioglicate
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6. History
• Non-ionic monomers
1969 Metrizamide (Amipaque®)
1974 Iopamidol (Isovue®)
1976 Iohexol (Omnipaque®)
1979 Iopromide (Ultravist®)
post 1980 Iopentol
(Imagopaque®),Iomeprol,Ioxilan.
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7. History
• Ionic dimers
1978 Ioxaglate(Hexabrix®)
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• Nonionic dimers
Post 1980
Iodecol
Iotrolan (Isovist®)
Iodixanol (Visipaque®)

8. Function of contrast media
• CM alters the attenuation of x-ray beam by altering the density of
related structures.
• The atomic no of the related structures also alter & helps in
visualisation of similar density structures within the region of
interest.
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9. Classification of CM
On the basis of physical properties:
• Negative Contrast Media.
• Positive Contrast Media
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10. Negative CM
• Gaseous substances which has low atomic number and specific weight,
absorb X-rays to a lesser extent than the surrounding body structures.
CO2
N2O
Air
O2
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11. Positive CM
• Substances which, because of their higher specific weight and atomic
number, absorb X-rays to a greater extent than the body tissues.
Barium sulphate
Iodinated contrast media
Contrast media for MRI and Ultrasound.
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12. Barium sulphate
• Ba Suspension is made up of pure Ba Sulphate.
• Particles of Ba must be small (0.1-3μm),which makes more stable in
suspension.
• Barium, having atomic no 56, is a good contrast agent for GI
examinations because it is very dense and won’t be absorbed by the
GI tract.
• In most situation it is diluted with water to give a lower density.
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13. Ba sulphate
• Solution has a pH of 5.3, which makes it stable in gastric acid.
• Examinations of different parts of GI tract require Ba preparation
with differing properties & different concentration.
• A non ionic suspension medium is used, otherwise its particles would
aggregate into clumps.
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14. Advantage of Ba
• Excellent coating which can be achieved.
• Allowing the demonstration of normal and abnormal mucosal
patterns.
• Economic because of lower cost.
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15. Iodinated CM
• Most of IV CM contain Iodine which has 53 atomic no. & 127 atomic
weight.
• Total iodine content in the body is 50 mg.
• It is Preferred because
 High contrast density due to high atomic
no.
Low toxicity.
•Conc ranges from 140-370mgI/ml.
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16. Iodinated CM
• They are water soluble .
• It is classified as:
Ionic
Non-ionic
Ionic monomers CM High-osmolar
Ionic dimer CM Low-osmolar
Monoionic/diionic
non-ionic monomer CM Low-osmolar
Non-ionic dimer CM. Iso-osmolar
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17. Ionic CM
• In solution, ionic contrast media ionize into two particles, i.e. the
cation and the anion.
• The anion in an ionic contrast medium is the triiodinated benzoic acid
part while the cation is usually sodium, calcium or meglumine.
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18. Ionic monomers
• Iodine to particle ratio is 3:2
• Sodium or meglumine act as cations.
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19. Ionic monomers
• Examples:
Iothalamic Acid
Has better neural tolerence but decrease
cardiovascular tolerence.
Eg. Conray
Diatrizoic Acid
Increase solubiliy
Decrease plasma protein binding & increase
glomerulus filtration.
Improves patient tolerence.
Eg. Urografin
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20. Ionic dimer
• Monoionic dimers ionize to give two particles but the number of iodine
atoms present is 6. Therefore the iodine atom to particle ratio is 6:2,
i.e.3 .Eg: Hexabrix.
• Diionic dimers ionise to give three particles (two cations and one anion)
with six iodineatoms present so that the iodine atom to particle ratio is
6:3, i.e. 2.
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21. Non-ionic monomer
• The molecule does not ionize & do not give two particles.
• Formed by replacing the cation radical portion of benzene ring with a
non-dissociating organic chain.
• It remains as one single molecule when in solution because of an amide
group on the acid part.
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22. Non-ionic monomer
• Less toxic effect becoz of removal of acid group & replacement of large
no of OH group which make them more hydrophilic.
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23. Non-ionic monomer
• These molecules do not ionize in solution so that the iodine to particle
ratio is 3:1. Therefore these are also ratio-3 molecules.
• Eg: Iohexol (Omnipaque), Ioversol (Optiray) Iopromide (Ultravist).
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24. Non-ionic dimer
• These molecules will give six iodine atoms for every molecule so that
their iodine atom to particle ratio is 6:1 which makes them ratio-6
molecules.
• Disadvantage is high viscosity becoz of relatively large size of molecule.
• Eg: Iodecol, Iotrolan (Isovist), Iodixanol (Visipaque®)
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25. Osmolality
• Osmolality is measure of no. of particles of solute in solution per kg
of water.
• Osmolality can be described as the property of a liquid to give up its
water to or to take up water from another liquid separated by a semi-
permeable membrane.
• Hypo-osmolar liquid gives up water to the second liquid.
• Hyper-osmolar liquid takes up water from the second liquid.
• Iso-osmolar liquids have the same osmolality and do not exchange
water.
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26. Osmolality
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Low and iso-osmolar compounds are tolerated
better by the body and give rise to fewer side
effects

27. Osmolality
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28. Osmolality
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29. Viscosity
• Viscosity is a measure of the flow properties of solutions.
• Iodine conc. determines the injection speed.
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30. Characteristics of an ideal IV CM
• provides maximum opacity to X-rays;
• is biologically inert;
• has high water solubility;
• is chemically stable;
• is selectively excreted;
• has a low viscosity;
• exerts minimal osmotic effects;
• is safe; and
• is not expensive
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31. Application of CM
•Contrast media may be introduced into the body via
The gastro-intestinal tract (oral or rectal).
Into the circulatory system (usually by the intravenous or intra-arterial
routes)
Into the cerebrospinal fluid (usually by the intrathecal route)
Directly into a duct or tract (e.g. lymph vessels, lacrimal duct, salivary duct,
etc).
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32. Contd…
• Barium Sulphate is used in GI tract:
Ba Swallow, 200-250% w/v.
Ba meal, 250% w/v.
Ba follow-through, 60-100% w/v.
Small bowel enema, 60% w/v.
Barium enema, 115% w/v.
CT of GI tract, 1-2% w/v.
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33. Contd…
• To achieve double contrast effect:
 for Oesophagus, Stomach & Duodenum-
CO2 & less often, air is used.
CO2 is administered orally in the form of
gas producing granules/ powder.
For large bowel, room air is administered
per rectum via hand pump attached to the
enema tube.
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34. 34

35. • Ionic CM
This type of CM can used in:
Fistulography
Sinography
HSG
MCU
RGU
CT GI tract (Oral CM)
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36. • Non-ionic CM:
This type of CM we can used widely.
IVU, CT , Angiography
Myelography- specially used Iohexol.
Arthrography of joint with air.
Non-ionic dimer are suitable for
bronchography.
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37. CM used in MRI
• 1981, first CM enhanced, ferric chloride in GI tract.
• 1984, gadolinium compound used as diagnostic IV MRI contrast agent.
• Now a days, frequently MRI examinations are performed with CM.
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38. Types of MRI CM
• Ferromagnetic
• Paramagnetic
• Super-paramagnetic
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39. Ferromagnetic
• Retain magnetism even when the applied field is removed.
• It may cause particle aggregation and cell function interference.
• So unsafe for MR contrast agents.
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40. Paramagnetic
• Have magnetic moments which align to the applied field
• Alignment return to normal after gradient field is turned off.
• May be made soluble by chelation and hence can be used IV.
• Maximum effect is on protons of water molecule, shortening the T1
relaxation time– increased signal intensity on T1 images.
• Eg: Gadolinium.
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41. Gadolinium
• Gadolinium is a rare earth metal “heavy metal”
• Gadolinium is chelated to diethylene triamine penta-acetic acid
(DTPA)
• Generic name is demeglumine gadopentate.(Magnevist)
• By binding DTPA to the Gadolinium sites, only one “free” gadolinium
site is available to attach to water molecules
• Diffuse freely & excreated by kidneys
• Gadolinium chelates are small mole. Wt. substance.
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42. Super-paramagnetic
• Are aggregation of paramagnetic ions in a crystalline lattice.
• cause abrupt change in local magnetic field which results in rapid
proton dephasing and reduction of T2 relaxation time – produce
decreased signal intensity on T2 images.
• Are less soluble than PM agents- so available only as colloidal
suspensions.
• Eg: Particals of iron oxide.
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43. USG CM
• Gas micro-bubbles are used
• Should be less than 7 μm.
• The gas molecules are encapsulated in palmitic acid, galactose or
albumen.
• US contrast media depend on interaction bet encapsulated micro-
bubbles and US beam.
• Allow imaging of vascular structures which cannot be evaluated even
with sophisticated doppler techniques.
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44. USG CM
•Levovist
Most widely used.
Microbubbles of air enclosed by a thin layer of
palmitic acid in a galactose sol.
Stable in blood for 1- 4 min.
•Echovist
Precursor of levovist
Bubbles in galactose but no palmitic acid.
Can’t pass thro pulm beds
Used for tubal patency.
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45. USG CM
• Albunex-
Sonicated air micro-bubbles coated with
human serum albumen.
Used in echocardiography.
Survives only a short time in left ventricle.
Little enhancement of arterial tree.
• EchoGen
An emulsion of dodecafluoropentane which
changes its phase converting into echogenic
gas micro-bubbles by hypobaric activation
prior to iv injection.
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46. USG CM
• SonoVue
An aqueous suspension of stabilised sulphur
hexafluoride micro-bubbles.
After reconstitution of the lyophilisate with
saline, the suspension is stable and can be
used for upto 4 hrs.
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47. Conclusion
• Use of contrast media helps for easy diagnosis of diseases by tissue
differentiation.
• Choice of CM depends on the type of procedure being performed.
• On going development of CM, more safe for patients.
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48. References
• A guide to radiological procedures: Stephen Chaman & Richard
Nakielny, 5th edition.
• Contrast media chemistry, pharmacology and pharmaceutical
aspects, John Stephen Forte.
• Clark’s special procedures. Latest edition.
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49. ???
• What is contrast media?
• Classify contrast media?
• What is negative CM?
• What is positive CM?
• Applications of contrast media?
• Differentiate ionic & non-ionic CM?
• What are the uses of double contrast technique?
• Characteristic of an ideal IV CM.
• Types of MRI contrast media.
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