oral contrast agents used in radiology with main focus on barium.

1. ORAL CONTRAST AGENTS
DR . ARUSHI GUPTA

2. BRIEF HISTORY
• 1896 -WALTER BRADFORD discovered contrast
media.
• 1897 - First reported GI contrast study performed
using Bismuth - TOXIC!
• 1910 - Barium Sulphate used (safer)
• 1920’s - Sodium Iodide used to treat syphilis.
Iodine was found to be radio opaque to x-rays.
Basis of all modern contrast agents.
• 1927 - First reported IVU with iodised organic salts
(Uroselectan)

3. INTRODUCTION
1) CONTRAST :
• It is the difference in the optical density between
different parts of image on radiograph.
• It depends upon absorption coefficient of different
tissues.
• Absorption is dependent upon :
Thickness
Density
Atomic number

4. 2)CONTRAST MEDIUM:
• It is a chemical substance of very high or
very low atomic number or weight,
therefore it increase or decrease the
density of the organ under examination.
Or
• A substance which when introduced into
the body will increase the radiographic
contrast in an area where it was absent or
low before.

5. 3)USE:
• Arteriography
• Angiography (DSA) – Cardiology
• Venography (replaced by ultrasound Doppler)
• IVU
• Fluoroscopy – Alimentary tract, hyserosalpingography,
sialography,
• CT
• MRI
• Ultrasound – Liver, kidney
• Myelography (replaced by MRI)
• Arthrography – Knee joints.

6. PHYSIOLOGY
• Concentration and excretion
1) >90%: passive glomerular filtration.
2) 1%: liver and intestine.
• Half life: 30-60 minutes.
• Do not enter the interior of cells.
• Rapidly excreted, over 90% being
eliminated by glomerular filteration by
kidneys within 12 hrs.
• Leaves the body within 24 hours(if
normal kidney) and weeks( if diseased
kidney).
EQULIBIRIUM BETWEEN INTRA AND
EXTRAVASCULAR SPACE IN 10 MINUTES
EXCRETED
EXTRAVASCULAR SPACE
IV CONTRAST

7. MODE OF ADMINISTRATION
1) Orally.
2) Rectally.
3) Intravenously – (injection/ infusion).
4) Mechanically – Filling of a body cavity or potential space
5) Intra-muscularly

11. CONTRAST MEDIA IN GIT
• Earliest medium used in the git was
iodized oil (lipiodol). However due to its
oily nature , it did not coat the mucosa.
• Later bismuth sulphate was used .
• At present the contrast medium of
choice is barium sulphate.

12. Reasons for using barium sulphate are :
• Barium has a high atomic number 56. Therefore it is
highly radiopaque.
• Non absorbable , non toxic
• Insoluble in water/lipid
• Inert to tissues
• Can be used for double contrast studies – it coats
the mucosa in a thin layer , thus allows the
introduction of 2nd or negative contrast agent
without significant degradation.
• Route: Orally Or Rectally (aqueous suspension with
0.3 to 1 g dry weight per milliliter)

13. Properties of ideal barium preparation
• Highly density for optimum
study
• Stable suspension which
doesn’t settle
• Should not flocculate with
secretions
• Low melting characteristics to
give a good and stable mucosal
coating

14. MANUFACTURE
• Barium sulphate is obtained from the mines by chemical precipitation
in order to remove the impurities.
STEPS :
1. Mined barium sulphate is reduced to barium sulphide (soluble)
2. Barium sulphide + sodium carbonate = barium carbonate
(poisonous)
3. Barium carbonate + sulphuric acid = insoluble barium sulphate

15. • The particle size can be reduced by processing the powder in a high speed
machine
• Average particle size ranges from 0.3um to 12um.
• 0.3um particles are used along with large particles to enhance coating and
suspending properties of large particles.
• Particles towards the size 12um are generally used for low viscosity , high
density barium.
• High density barium contains a mixture of different sized particles , that also
results in increased viscosity.
• Viscosity can be reduced by the addition of additives and suspending agents.

16. DILUTION
There are 3 systems to describe a particular dilution
1) Weight by weight – w/w suspension
Specified weight of barium sulphate is used and enough water is then
added to obtain a certain total weight .
Eg. 30% w/w suspension is to weigh 30g of barium sulphate and add
70g of water to it for a total wt of 100g

17. • Weight by volume – w/v suspension
Here a specified weight of barium sulphate is determined and
enough water is added to obtain a certain total volume .
Eg 80% w/v suspension is to weigh 80gm barium sulphate and to add
enough water to make the total volume upto 100ml suspension.
• Volume by volume – v/v suspension
Not recommended.
Specific gravity :
SG = weight of 1 litre of barium solution / weight of 1 litre of water

18. • Commercially prepared barium formulations in
india are manufactured by M/s Eskayef Fine
Chemicals Ltd. Under the brand name
‘MICROBAR’ in the following specifications:
1. Microbar paste : 100% high viscosity paste.
High density , high viscosity preparation used
for conventional study of the pharynx and
oesophagus.
2. Microbar suspension: 95% moderate density
and viscosity suspension for oesophagus ,
stomach and small intestinal studies. Marketed
in one litre bottles.

19. • Microbar HD: 200% high density, low viscosity
preparation, supplied in powder form. By
adding 70 ml of water to this and shaking the
tumbler pack the desired amount of
suspension is formed which is ideal for double
contrast studies for oesphagus , stomach and
duodenum . sachets of gas producing powder
are supplied with this pack.
• Microbar for enema : one and five kg packs of
powder are available. Desired suspension can
be made.

20. How to prepare your own barium suspension?
• To prepare one litre of 50% suspension , take a small amount of water ( about
200 ml ) and add 5 gm of carboxy methyl cellulose (C.M.C) to it and mix well.
• Take 500gm of barium sulphate powder and add a little of it at a time to the
water , mixing continuously till a thick paste is formed. This will prevent
formation of clumps of the barium.
• To this paste add enough water to make up the volume of the mixture to one
litre and mix it well
• Then add the preservatives , antifoaming agents and antacids.
• The whole mixture should be mixed for 15 minutes
• This type of preparation should not be diluted otherwise it will tend to settle.
• The preparation should also not be stored for a long time

21. Characteristics influencing coating :
• Additives
Are added to influence the rate of settling, viscosity, charge, musical
coating , thickness and flocculation.
It too much additive is used, the viscosity will be so high that the
suspension flows only with difficulty.
• Density
Appropriate density is achieved by making the suspension using the
required weight of BaSO4

22. • Stabililty
It indicates that the suspension will not settle down when allowed to
stand.
Suspending agents like gum acacia or CMC are used.
These agents increases viscosity hence should be used in minimum
amount to attain the required stability.
The suspension is considered to be of adequate stability if it does not
settle at the rate of more than 1/10 at the end of 3 hours.

23. • Flocculation
Is the reduction in the number of particles by the formation of larger masses.
When the suspension comes in contact with ionic solutions like gastric and
intestinal secretions , the suspension will form clumps.
To prevent this, antacids are added which will neutralize the gastric acid and
prevent flocculation.
Antacids used :
Sodium citrate ( commonly used )
Aluminium hydroxide
Magnesium sulphate

24. • Preservatives
Plain barium is inert. Since additives are added to it , we get fungal growth. So
preservatives are added.
Previously methyl paraben was used.
Now sodium metabisulphate is used.
• Antifoaming agents
Simethicone or methylpolysiloxone are added to prevent formation of air
bubbles which mimic polyps(artifacts).
They act by reducing the surface tension of the gas bubbles enabling them to
coalesce thus facilitating gaseous release.

25. • Colouring agent
Erythocin is used
• Sweetening agent
Fruit essences are used to mask the unpleasant
taste of barium.

26. ADVERSE EFFECTS
• Chemical peritonitis due to extravasation of additives.
• Extravastion into brochial tree , urinary tract will produce inflammation.
• Barium inspissation in cases of colonic obstruction to form hard stones.
• Intravascular entry can cause embolism
• Appendicitis – not proved
• Barium encephalopathy
small amount of barium can be absorbed from the peritoneum in case of
perforation can enter circulation . It can concentrate in CSF
• long standing barium deposits are carcinogenic

27. CONTRAINDICATIONS
• Integrity of gut wall compromised or GI Perforation.
• Previous allergic reactions to barium.
• Suspected fistula between oesophagus and lung.

31. Other contrast media used :
• GASTROGRAFFIN
20ml of urograffin 76% + 20 ml of normal saline + 2 drops of sorbitol
(melting agent) which gives a better mucosal coating. Mix thoroughly
Water soluble high osmolar ionic iodine based contrast

32. Indications :
• Suspected perforation
• Suspected fistula
• History of recent biopsy
• Suspected lower intestinal obstruction
• Corrosive poisoning
• Meconium ileus
• Immediate post operation status
• Paediatrics

33. • NON IONIC CONTRAST MEDIA
Low osmolar contrast media give better opacification of the git and
cause less electrolyte disbalance and can delineate small intestine
better than ionic media due to less dilution.
But they are expensive.

34. • ORAL COCKTAIL
Mixture of barium sulphate , magnesium sulphate and a low osmolar
non-ionic contrast media.
The latter two absorb water into the bowel and dissolve barium
sulphate.
Therefore barium moves very fast in the git .

35. • AIR/CO2
To diagnose intussusception.
• WATER
To diagnose lipomatosis of colon which appears more lucent compared
to the water column

36. CONTRAST MEDIA FOR CT IN GIT
• FOR STOMACH AND SMALL BOWEL
Adequate bowel opacification and distension is required.
Ideal gut contrast agent :
• Should fill the entire bowel lumen
• Should be palatable
• Non irritating to the intestinal mucosa
• Should pass rapidly through the git without producing
artifacts
• Should coat the gut mucosa

37. • A positive contrast should increase the CT attenuation by atleast 40HU. This
can be done by using dilute solutions of water soluble media or dilute
suspension of BaSO4.
• A solution of 2-3% meglumine diatrizoate increases the CT attenuation value.
Although water soluble contrast agents pass rapidly through the gut ,
 they do not coat the gut wall
 have a poor taste
 Become diluted as they reach the terminal ileum , thus distal small bowel
may be poorly demarcated.

38. • FOR COLON
Colon and rectum may be opacified using dilute iodinated solutions 1-2%
as a 200-600ml enema.
Air contrast studies have recently been advocated as the method of choice
to evaluate the colon.
This is contraindicated in acute diverticulitis , inflammatory bowel disease
or radiation proctitis.

40. CONTRAST MEDIA FOR MRI IN GIT
• Dual aim : improving anatomic
delineation and permitting better
diagnosis of functional disorders.
Ideal gut contrast agent :
• Chemically stable
• Preferably non-metabolizable and
rapidly eliminated
• Inexpensive and easily synthesized.
• Non-toxic

41. POSITIVE CONTRAST
Water soluble
• Ferric ammonium citrate
• Manganese chloride
• Metal chelates including Gd-
DTPA
Water insoluble
• olive oil
• NEGATIVE CONTRAST
Water soluble
CO2 tablets
Perfluorocarbons
magnetites

42. THANK YOU