BARIUM INTRODUCTION.pptx

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1. CONTRAST MEDIA USED IN GIT

2. CONTRAST MEDIA Contrast media is a liquid or solid substance or gas which increase the image contrast of anatomical structure which normally cannot be easily visualized or distinguished from surrounding tissue. Contrast media is usually specific to the image modality and organ system

3. Contrast media classification Positive contrast media Radio opaque BaSO4/Iodinated contrast/oily contrast media Negative contrast media Radiolucent Air/gas/co2 water soluble water insoluble BaSO4/oily Iodinated contrast

4. D ifferentiation b/w positive and negative contrast SINGLE CON TRAST STUDY BE DOUBLE CONTRAST STUDY BE

5. INTRODUCTION The earliest contrast medium used in the GIT was iodised oil ( lipiodol ). However, due to its oily nature, it did not coat the mucosa. Hence, later, Bismuth sulphate came to be used. At present the contrast medium of choice is Barium sulphate.

6. The reasons for using Barium sulphate for GI studies are Insoluble white powder used in GIT Ba has a high atomic number 56. I t is highly radiopaque Insoluble in water/lipid. Inert to tissues. Can be used for double contrast studies Barium will not dissolve in alcohol/water/lipid Barium is mixed with water and some ingredients to make the contrast agent. Non-absorbable and non-toxic Easily excreted via feaces .

7. PROPERTIES OF AN IDEAL BARIUM PREPARATION 1. High density for optimum study being performed. 2. Stable suspension which does not settle. 3. Should not flocculate with secretions. 4. Low melting characteristics to give a good and stable mucosal coating

8. MANUFACTURE Barium sulphate is obtained from the mines by chemical precipitation in order to remove the impurities.

9. 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. The particle size can be reduced by processing the powder in a high speed pounding, machine. Average particle size of precipitated barium sulphate ranges from 0.3 µm to ≃ 12 µm. 0.3 µm particles are used along with large particles to enhance coating and suspending properties of large particles. By themselves small particles resist wetting. Particles towards the size of 12 µm are generaly used for low viscosity, high density barium. High density barium contains, a mixture of different sized particles, that also results in increased viscosity.

10. Viscosity can be reduced by the addition of additives and suspending agents, which are proprietary, e.g., microbar H.D. 200% w /v _for double contrast studies of upper G.I. Tract . BaSO4 being insoluble in water, is used in the form of a suspension . The concentration of the suspension is indicated by weight/volume. E.g .: 100% suspension contains 100 gm of BaSO4 in 100 ml of prepared suspension .

11. DILUTION THERE ARE 3 SYSTEMS TO DESCRIBE A PARTICULAR DILUTION. Weight by weight - wlw suspension Specified weight of Barium sulphate is used and enough water is then added to obtain a certain total weight. E.g.: 30% w /w suspension is to weigh 30 g of Barium sulphate and add 70 g of water to it for a total wt. of 100 g. (1 gm of water = 1 ml of water). 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. E.g.: 80% w /v suspension is to weigh 80gm Barium sulphate and to add enough water to make the total volume upto 100 ml suspension.

12. Volume by Volume - vlv suspension. This system is possible but not recommended. A unit volume of dry barium sulphate can vary considerably, depending on the degree of packing. Thick and thin barium are meaningless terms. Weight of 1 litre of Barium solution ------------------------------------------------ Weight of 1 litre of water Specific gravity: S.G

13. Mixing This is a very important step to assure a stable suspension. Use of a high speed and high shear mixer ensures melting of the Barium sulphate particles and also mixes the particles evenly in the suspension. This ensures that the suspension is stable. It should be mixed for atleast 15 min. continuously, to assure stability just before the suspension is administered. Commercially prepared Barium formulations in India are manufactured by M/ s. Eskayef Fine Chemicals Ltd. under the brand name of 'MICROBAR' in the following specifications.

14. Microbar paste: 100% W/V 2. Microbar suspension: 95% W/V 3. Microbar HD: 200% high density, low viscosity 4. Microbar for enema : One and five kg packs of powder are available MICROBAR

15. Microbar paste: 100% high viscosity paste in collapsible tubes. This is a high density, high viscosity preparation used for conventional studies of the pharynx and oesophagus .

16. 2. Microbar suspension: 95% moderate density and viscosity suspension for oesophagus , stomach and small intestinal studies. Marketed in one litre bottles.

17. 3. Microbar HD: 200% high density, low viscosity preparation, supplied in a powder form in a tumbler pack. By adding 70 ml of water to this and shaking the tumbler the desired amount of suspension is formed which is ideal for double contrast studies for oesophagus , stomach and duodenum. Sachets of gas producing powder are supplied with the pack.

18. 4. Microbar for enema : One and five kg packs of powder are available. Desired suspension can be prepared.

19. 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 500 gm 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, antifoarning agents and antacids. The whole mixture should then be mixed for 15 minutes, using a high speed mixer to form a good suspension. 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.

20. ADVANTAGES OF BARIUM SULPHATE PREPARATION Non-absorbable. Therefore Barium does not get degraded throughout the bowel. Suitable for double contrast studies as it coats the mucosa in a thin layer, thus allows the introduction of 2nd or negative contrast agent without significant degradation. Low cost Excellent coating Easily excreted in GIT. Excellent mucosal coating Demonstration of mucosal pattern.

21. DIASDVANTAGES OF BASO4 High morbity-peritonitis (impaction/constipation) Aspiration Intrastation-pulmonary embolus

22. CHARACTERISTICS INFLUENCING COATING 1 . ADDITIVES Additives are added to influence the rate of settling, viscosity, mucosal coating, thickness and flocculation. If too much of an additive is used, the viscosity will be so high that the suspension flows only with difficulty. Exact additives added by the manufacturers are kept as a trade secret, but a varied range of additives can be used when we prepare our own Barium sulphate suspension to achieve the required properties .

23. The appropriate density is achieved by making the suspension using the required weight of Barium sulphate powder. Measuring Barium powder using cups cannot be a standard preparation because the compactness of filling the cup will vary. In addition the powder at the top of the packet is made up of larger particles and hence will have lesser weight as compared to the powder at the bottom which is finer and more compact. 2.DENSITY

24. 3.S TABILITY It indicates that the suspension will not settle down when allowed to stand. Suspending agents like Gum acacia or carboxyrnethyl cellulose (CMC) are used to prevent settling. These agents increase the viscosity of the suspension, 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. CMC is hygroscopic, therefore retains water and prevents settling of the particles. Hence it prevents sedimentation and size of the particle remains the same.

25. 4.FLOCCULATION 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 intestinal or gastric secretion, the suspension will form clumps. To prevent this, antacids are added which will neutralise the gastric acid and prevent flocculation. They will also make the suspension alkaline so that the intestinal secretions which are alkaline will not cause flocculation. Antacids used are • Sodium citrate (commonly used). • Aluminium hydroxide. • Magnesium sulphate.

26. 5.Preservatives Plain Barium sulphate is inert. Since additives are added to it, we get fungal growth. So preservatives are needed. Previously Methyl paraben was used. Now Sodium metabisulphate is used. 6.Antifoaming agents Simethicone or Melthylpolysiloxone 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 .

27. 7.COLORING AGENT Erythrocin is used. 8.Sweetening agent Saccharine or fruit essences are used to mask the unpleasant chalky taste of barium and produce less nausea. Chocolate is not commonly used because of possible allergic reaction.

28. ADVERSE EFFECTS 1. Chemical peritonitis due to extravasation of additives of Barium sulphate. 2. Extravasation into bronchial tree, urinary tract and other body cavities will produce inflammation. 3. Barium inspissation in cases of colonic obstruction to form hard stones. 4. Intravascular entry of Barium can cause embolism. 5. Appendicitis-not proved. 6. Barium Encephalopathy. Small amount of Barium can absorbed from the peritoneum in case of perforation j, Circulation j, Concentrates in CSF with detectable levels j, Encephalopathy 7. Previous contrast media extravasated may mimic cancer due to inflammation. Longstanding barium deposits are carcinogenic.

29. OTHER CONTRAST MEDIA USED Gastrograffin 20 ml of Urograffin 76% + 20 ml of Normal Saline + 2 drops of Sorbitol (melting agent) which gives a better mucosal coating. Mix thorough! y. Indications Suspected perforation. 2. Suspected fistula. 3. History of recent biopsy. 4. Suspected Lower Intestinal obstruction. 5. Corrosive poisoning. 6. Meconium ileus/plug syndrome. 7. Immediate post operation status.

30. Non-ionic Contrast Media Low osmolar contrast media give better opacification of the GIT and due to low osmolarity because less electrolyte imbalance and can delineate small intestine better than ionic media due to less dilution. But they are expensive . 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. Air/CO2 To diagnose intussusception. Water To diagnose Lipomatosis of colon which appears more lucent compared to the water column.

31. CONTRAST MEDIA FOR CT IN GIT Techniques employed in CT are chosen to maximize delineation of normal anatomic structures, accurately identify pathologic processes and ensure optimal utilization and operational efficiency. For Stomach and Small Bowel To a large extent, the sensitivity of CT in diagnosing pathology depends on adequate bowel opacification and distension, as the basic radio pathologic finding in a variety of diseases is thickening of the intestinal wall. Therefore, the gut in question must be distended and filled with a contrast agent. That permits the wall of the bowel to be assessed accurately.

32. CONTRAST MEDIA FOR CT IN GIT

33. THE IDEAL GUT CONTRAST AGENT • Should fill the entire bowel lumen • Should be palatable • Non-irritating to the intestinal mucosa • Should pass rapidly through the GI tract without producing artifacts or stimulating vigorous intestinal peristalsis. • Preferably the contrast media should coat the gut mucosa so that the presence of bowel lesion is detectable when the lumen is not distended. A positive contrast material must increase the CT attenuation value of bowel lumen at least by 40HU.

34. This can be done by using dilute solutions of water soluble media or dilute suspensions of Barium sulphate. Conventional BaSO4 suspension are too dense resulting in streak artifacts when administered. The commercial introduction of dilute 1-2% BaSO4 solutions containing special suspending agents has permitted dilute barium to remain homogeneously suspended as it passes through the GI tract. A solution of 2-3% Meglumine diatrazoate increases the CT attenuation value of the gut enough to permit a reliable differentiation from the surrounding tissues. Although water soluble contrast agents pass rapidly through the gut, they do not coat the gut wall and have a poor taste.

35. SPECIAL TECHNIQUES • Glucagon injection (0.1 mg iv / im ) can be used for reducing gut motility and motion artifacts. • Octapeptide injections to briefly stimulate small bowel peristalsis. • Metaclopramide 10 mg orally, 45 minutes before CT study rapidly empties the stomach and improves opacification of ileum. COLON Colon and rectum may be opacified using dilute iodinated solutions 1-2% as a 200-600 ml enema.

36. CT RECTAL CONTRAST

37. Air contrast studies have been recently advocated as the method of choice to evaluate the colon. This is contraindicated in acute diverticulitis, inflammatory bowel disease or radiation proctitis

38. CONTRAST MEDIA FOR MRI IN GIT GI contrast agents for MRI are being developed with the dual aims of improving anatomic delineation and permitting better diagnosis of functional disorders. Ideal Characteristics for MRI contrast • Chemically stable. • Preferably non- metabolisable and rapidly eliminated. • Inexpensive and easily synthesized. • Non-toxic in doses appropriate for contrast enhancement .

39. Positive Contrast Agents Water soluble: • Ferric ammonium citrate. • Manganese chloride. [e.g., Lumentlance-Bracco ] • Metal chelates including Gd -DTPA. • Olive oil Negative Contrast Agents Water soluble: • CO2 tablets • Perfluorocarbons • Magnetites • Side effects-Relatively safe Castro intestinal side effects are the commonest among the minimal side effects.