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Body of human consists of soft tissues and bony structures. As among the soft tissues itself, there are very little differences in density to provide enough contrast to visualize the anatomic details. It is necessary to differentiate the density of the organ to provide desired contrast. The factor associates with the contrast include the characteristic of the tissues that comprise the anatomical part, technical factors utilized, characteristic of the images receptor; automatic processor and contrast media agents. The usage of the contrast media has increase as there are developments in technology. Contrast media is use in computer tomography (CT), magnetic resonance imaging (MRI) and digital subtraction angiography (DSA). Some other familiar procedures include barium enema, excretory urograms and barium meal or swallow.
Contrast media is a substances that is used to increase contrast structure or fluid in the body.Contrast media is usually used to visualization and differentiation of soft tissue structure.Contrast media is used because soft tissues more difficult to demonsrate than bony structure (usually used for blood vessels and gastrointestinal tract).Contrast agent that usually used is iodine or barium.
The contrast media is divided into two (2) groups or types; negative contrast agents (radiolucent) and positive contrast agents (radiopaque). Negative contrast media agents or also called radiolucent material is the material that allows x-ray to pass through it because of its low atomic number. Examples of radiolucent or negative contrast media are air, oxygen, carbon dioxide and nitrous oxide. Negative contrast media is already filled inside the anatomical areas such as lung. Any anatomic area which filled with negative contrast media appears darker on radiograph images.
They are categorized as drugs because they can be absorbed into the systemic circulation and may affect a physiologic response.When an anatomical area is filled or outlined by these agents,the images of the organ appears to be white (positive contrast) whereas negative agents make the organ appear dark.
GASTRO-INTESTINAL TRACT (GI)
Barium sulphate or white chalky isoluble in water is usually used to increase contrast in gastrointestinal tract.Barium sulphate almost same as 'iodine' in terms of contrast qualities,but it cannot be absorbed by the body.Therefore good choice for GI studies.But,not suitable if a perforated stomach or intestine is suspected (barium comes out and go to peritoneal cavity and cause death).
In such cases water-soluble iodine contrast agent is used because it is easily absorbed if spillage into abdominal cavity occurs.Allergic reactions almost nonexistent withBaSO4.
BaSO4 is used for GI tract and administered orally or rectally as an example Barium enema.
Allergic reactions to latex enema tips can cause anaphylactic responses.Other contrast media include gastrografin,useful if a rupture of GI tract suspected as an example perforated ulcer ruptured appendix.Unlike BaSO4 gastrografin is easily absorbed into the blood stream.
Intravascular contrast agents is iodined based.It is organic mixed (non-ionic) or ionic.Organic agent with iodine has side effects because it is not separate into molecule.There are side effects because it is injected with high osmolar solution.As an example,it sends more iodine atom to every molecule.If the iodine content is high,x-ray effects will be more high.
The old type of contrast agent type,Thorosthat is based on thorium dioxide,but it is useless because it is turn to carcinogenic (can cause skin cancer) .There are many difference molecules.
Example of the iodine molecule is iohexol,iodixanol,ioversol.Contrast media that based on iodine is water-soluble and not dangerous to body.This contrast agents is commercial as colourless-solvent.Usually this contrast agent is used in intra-artery,intrathecally likes in discography (back bone) and intra-abdominal.
TYPES OF CONTRAST MEDIA
There are two types of contrast media,positive agents and negative contrast agents.The negative agents is carbon dioxide and air,used to decrease organ density to produce contrast.The positive agents is barium and iodinated contrast media.They produce increase density difference by creating white or opaque areas on the image.
There are solution or gases introduced into the body to provide contrast between an organ and its surrounding tissue.
There are three types of contrast media,iodined based,barium based and air or gases.
Iodined contrast media usually classified into ionic and non-ionic.This iodined contrast media have high osmolarity value and many side effects likes urografin,telebrics,gastrografin and mores.Non-ionic contrast media,has low osmolarity value and don't have side effects likes omnipect,ultravist,visipect and mores.Both of this contrast media usually used at radiology department,because of the dangerous reactions with body and the solvent.It is usually used prior to increase contrast of blood vessels and changes of tissue,but it can be used for urination tract,uterus and fallopian tube.It can cause patients fells to pass urine and also feels like metal at the lips.
Iodine contrast agents usually used for Angiogram (artery studies) ,Venagram (vena studies), VCUG (voiding cystourethrography) and IVU (intravenous urography).
Oil-based iodine contrast media are made of fatty acids found commonly in plants and animals. Oil-based iodine contrast media are insoluble in water and not flow easily it relatively viscous. Oil-based iodine contrast media are decomposed when exposed to light, heat or air. Therefore, it should be stored in a cool, dark area. Don't attempt to use any media of contrast that have darkened from their original pale yellow or pale ember color because the dark color indicates that they have decomposed.
Barium sulphate usually used in digestive system imaging.Materials that exists as white chalky,insoluble-water made up from mud that mixed with water and inserted into the intestine tract (gastrointestinal tract). Barium sulfate is one (1) of type used in radiography. Barium sulfate with atomic number of 56 is radiopaque. Barium sulfate is not soluble in water therefore it requires to be shaken or mixed into suspension in water. Depending on the environment of the barium sulfate, such as acid in the stomach, it has tendency to clump and progress suspension called flocculation. Any stabilizing acids such as sodium carbonated usually use to prevent flocculation.
Barium sulfate suspension must be concentrated enough to absorb x-ray. But these suspensions must able to flow easily yet coats the lining of the organs. Barium sulfate is applied to the procedure of study to the small intestine and oral formulations. For the study of the lower bowel or lower intestinal, barium sulfate is recommended to be mixed with water to reduce irritation to the colon and yet to help patient to hold the enema during the examination. Administration of the barium sulfate can cause complication. If patient is suspected to have perforation in digestive tract, barium sulfate is contraindicated. This is because the barium sulfate is not naturally absorbed by body, if it enter the area of cavities like peritoneal cavity or pelvic cavity may cause peritonitis and must be surgically removed.
There are five types of barium,barium enema (large intestine studies),barium swallow / meal (oesophagus studies),barium meal (stomach studies),barium follow through (stomach and small intestine studies) and CT Pneumocolon / virtual colonoscopy.
CLEANSING ENEMA OR BOWEL PREPARATION FOR BARIUM STUDIES(BARIUM ENEMA)
This is particularly for patients undergoing barium studies of the lower GIT.There are many ways of bowel preparation according to the radiologist,saline enema,hypertonic enema,soap suds enema,barium enema (to diagnose pathological conditions of the lower GI tract).Cleansing enema is filling the colon with the liquid such as normal saline to flush out fecal contents.Ensure catheter inserted into rectum.
Normal saline is the safest solution for cleansing enema is because it has the same osmolarity as that in the interstitial space that surround the colon.Therefore it will not change the fluid balance in the body and also well tolerated by infants and children because of the very little change in the fluid and electrolyte balance.
SELECTION OF CONTRAST MEDIA
It is ability to mix with the body fluids (not toxic to body),viscosity (thickness of fluid / solution),ionic strength (molecular concentration),osmolality (weight of the ion) and potential for toxicity.
EXPECTED SIDES EFFECT
Medical conditions can cause by any inserted of contars media.There are reactions can happen from small to serious and sometimes can cause death.Iodine contrast agent is safe drugs,negative reactions is exixts but not always happen.Expected side effects are flushing or warm feelings,nausea and or vomiting,headache,altered taste,coughing,dyspnea,rapid pulse,rapid respiration,shock,seizures and cardiac arrest.
This reactions occur to contrast injection via oral or rectum and also retrograde piligram.The reactions is same like anaphylactoid reactions, but it is not caused by igE-mediated imunisation reactions.Patients that has contrast reactions,has high risk to get anaphylactoid reactions.Treatments before contrast is injected with corticosteroid has shown increasing of negative reactions.
Small(no need treatment),vomiting and bleeding stool,medium,irritation on skin,asthma and serious (threaten lifeand need intensive treatment) is difficulties in breathing.
Cointrast did not even give to patient unless doctor is helping to avoid any allergic reactions.Usually patient is asking before giving the contrast media (doctor ask the patient) includes if patient has any allergic reactions,asthma or diabetes.
"Nephrotoxicity" (toxicity at the kidney) is undergoes examination using contrast media of iodine based.Kidney that not functioning (creatinine more than 2oo micromole/litre) well only giving contrast media if needed.At the conditions,specifics contrast media is better for kidney,can giving to avoid contrast induced nephropathy.
Metformin,an diabetes oral anti-agent,stops for 48 hours because of injection contrast media intravascular and metformin uses not continues until the kidney starts to functioning in normal state.This is because if contrast media cause kidney damage and patient take metformin continuously (secretes by kidney),maybe there are toxic in metformin,increase the 'lactic acidosis'.dangerous / serious complication.
INCREASE MAGNETIC RADIATION SIGNAL
It is include gadolinium for uses in MRI (magnetic reasonance imaging) as contrast agents.At the 3+ oxidation,metal have seven electron not repaired.This cause water at agent contrast surrounding relax immediately,increasing scanning of MRI quality.
Microbubbles contrast agents is used in sonography especially ecacardiogram to detect heart storage.This bubbles is from a little nitrogen amount or fluorocarbon and helps with protein,lipids or polimer.Decreasing density on internal surface between gas in bubbles and fluids surrounding and ultrasounds is reflacts out.
Sistolic blood pressure (less than 8ommHg),heart not functioning well,diabetes and kidney not functioning well.