Contrast media are substances is used to highlight areas of the body in radiographic contrast is to surrounding tissues. The contrast media is enhance the radioopacity and optical density of the area must under investigation so that the tissue or structure absorption differentials are sufficient to produce adequate contrast used with adjacent structures. When used for imaging purposes contrast media can be administered by injection and must be insertion or ingestion. Radiographic contrast has been used to enhance the contrast of radiographic images, is inspired air became the first recognized contrast agent in radiographic examination of the chest. The first iodine based contrast is used was a derivative of the chemical ring pyridine. It meanings it can be employed for the examinations such as angiography and computed tomography (CT).
REQUIREMENTS OF THE IDEAL CONTRAST MEDIUM
Currently there is no contrast medium on the market that is must considered to be ideal, but the ideal of contrast medium should fulfill certain requirements for safe and affective application. It should be easy to administer, must non-toxic, it is a stable compound. Another ,it is are concentrated in the required are must be injected. Contrast media are divided into two main categories. The first is are negative contrast media which are radiolucent and of low atomic number causing the part in which it is placed to be more readily penetrated by x-ray than the surrounding tissue. Gases are commonly used to produce negative contrast on radiographic image. The second type is positive contrast media it these are of a high atomic number , causing the part in which placed to be less readily penetrated by x-rays than the surrounding tissue. Barium and iodine based solutions are used in medical imaging to produce positive contrast. Both positive and negative contrast can be employed together in double contrast examinations to produce a radiographic image. Double contrast examinations permit optimum visualization by producing a high inherent whilst allowing adequate penetration of the area under examination. Large amounts which may be dense enough to mask important information.
NEGATIVE CONTRAST MEDIA
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Introduced by the patients during a radiographic examination, inspiration during chest radiography or can also be introduced by the radiographer as part of the examination in a double contrast barium enema.
Introduced into cavities of the body for example in the knee when performing an arhrogram to demonstrate the knee joint.
Introduced into the gastrointestinal tractin conjuction with a barium sulphate solution to demonstrate the mucosal pattern,double contrast barium meal.For the barium meal it is formulated as effervescent powder Carbex granules or readily mixed carbonated barium sulphateBaritop.Carbon dioxide can also be introduced inti the colon when performing a double contrast barium enema.
POSITIVE CONTRAST MEDIA
Barium and iodine solutions are used to create positive contrast on images.
Barium sulphate solutions used in gastrointestinal imaging
High atomic number producing good radiographic contrast, insoluble, stable, relatively inexpensive ,excellent coating properties of the gastrointestinal mucosa. Barium sulphate mixed with additives and dispersing agents ,held in suspension in water. Also added to the suspension is a defoaming agent ,employed to prevent bubbles that may mimic pathology in the gastrointestinal tract. Flavourings are usually added to oral solutions, making them more palatable for patients. Patients rarely have allergic reactions to barium sulphate solutions but may react to the preservatives or additives in the solutions. Barium sulphate preparations are usually safe as long as the gastrointestinal tract. If barium sulphate escape into the peritoneal cavity ,inflammation and peritonitis may occur. Escaped barium in the peritoneum causes pain and hypovolaemic shock and, despite treatment which includes fluid replacement therapy ,steroids and antibiotics ,there is still a 50% mortality rate of those who survive,30% will developed peritoneal adhesions and granulomas. When preparing the barium solutions for administration it is important to check expiry dates and ensure the packaging is intact. Solutions administrated rectally should be administrated at body temperature to improves patient tolerability and also reduce spasm of the colon. Barium sulphate solutions are contraindicated for the following pathologies, suspected peforation, suspected fistula or to check an anastomosis site, suspected partial or complete stenosis, paralytic ileus, haemorrhage in their the gastrointestinal tract, toxic megacolon, prior to surgery or endoscopy, if the patient has had a recent gastrointestinal wide bore biopsy usually within 3-5 days. These can be administrated orally, rectally or mechanically via stomas. The patientâ€™s consent must be given prior to the administration of barium contrast solutions. The patient should be reassured about the examination and given the opportunity to ask questions.
Iodine-based contrast media in medical imaging
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The largest group contrast media used in imaging departments are the water soluble organic preparations in which molecules of iodine are the opaque agent. The carrier molecules are organic, containing carbon, and are of low toxicity and high stability. The iodine based compound are divided into four groups depending upon their molecular structure, ionic monomers, ionic dimmers ,non-ionic monomers, non-ionic dimmers
These are low osmolar agents and do not dissociate into two particles in a solution, making them more tolerable and safer to use than ionic contrast.
PATIENT SELECTION AND PREPARATION
There are three main objectives, namely to ensure patients in the preparation of contrast media used according to the patient's condition and patient indications. Besides reducing the risk of negative reactions to contrast media are given. The last objective is the preparation of athletes for any emergency in the event of a reaction to contrast media. While the understanding of the history of the patient diagnotic essential to the proper preparation of contrast media and is compatible with the patient. Diagnotic patient's history should be ascertained and must not fall into the category of contra indications.
CONTRAST MEDIA injection
To perform this task, the cooperation of the patient during the injection is absolutely necessary because it can prevent the leakage of contrast media of blood vessels during injection. if the patient complained of pain or swelling at the injection occurs, immediately stop the injection. The most important injection should be performed using power injection through a flexible plastic cannula. Additionally, must control the flow rate appropriate to the size of the catheter is used. size 22 gauge can menghaslkan 5ml/sec. while the size 20 gauge or more are to flow 3ml/sec or more. Antecubital are blood vessels most suitable for power injection. injection power supply must be done carefully so as to avoid leakage of blood vessels during injection. current injection, communication with patients is very important. If any problems occur, the injection should be stopped immediately.
NEGATIVE EFFECTS OF THE USE OF CONTRAST MEDIA
TYPE OF REACTION
Circumstances in which the patient will feel nauseated or vomit. This reaction does not require special treatment where the patient will return to normal after 20 to 30 minutes.
This reaction is not harmful to patients, but requires treatment. This situation occurs with some symptoms such as uricaria, vasovagal reaction, and mild bronocospasm. This reaction requires careful observation until the patient returns to normal.
This category of reaction is extremely rare. smpton patients will experience such as shortness of breath, diffuse erythema, and cardiac arest. patients need immediate treatment for their risk to the patient's life.
Contrast media is a chemical used in the procedures or special techniques to improve the quality of diagnostic imaging radografi in terms of clarity of an image. using contrast media, the resulting images can help the process be made more precise diagnostic and easy.