What Is Contrast Media In Radiology?

The contrast media is chemical substances which is use to visualize the internal structure and function of the human body organs. The contrast gives the better differentiation. Contrast media are commonly used to improve the visibility of blood vessels and the gastrointestinal tract.

A radiographic contrast agent is a substance that is administered to a patient during an imaging examination to improve its diagnostic performance. Contrast agents are most often administered via the intravenous (IV) and oral routes for computed tomography (CT) and magnetic resonance imaging (MRI) examinations. However, other routes of contrast administration may be utilized, depending on the particular imaging study to be performed. For example, arteriography requires the intraarterial (IA) administration of contrast material, while arthrography requires the intraarticular injection of contrast material directly into a joint. Intrathecal contrast administration is required for myelography.

A catheter is used to inject the contrast material in some procedures. In hysterosalpingography, a catheter or cannula is placed into the external cervical os to opacify the uterine cavity. In retrograde urethrography, a Foley catheter is placed at the urethral meatus in a male to inject contrast material to evaluate the urethra. In cystography, injection of contrast material is performed through a catheter placed in the urinary bladder. In retrograde pyelography, contrast material is administered through catheters placed into the renal collecting systems with cystoscopic guidance to evaluate the pyelocalyceal systems and ureters in patients who cannot receive intravenous contrast material.

Types Of Contrast Media.

There are Mainly Two types of contrast media.

1) Positive contrast media

2) Negative contrast media

1) Positive contrast media:– The contrast media, which have high atomic number and specific weight is called positive contrast media. The positive contrast media increase the beam attenuation. Ex. Barium sulphate, iodine compound.

There are two types of positive contrast media.

A) Barium based contrast media:– The barium sulphate used in the examination of gastrointestinal study. It is the water soluble contrast media which is always given by oral and rectally and directly in the lumen.

B) Iodine based contrast media:- The ionic contrast media contain cation and anion ions. The cation is a positive charged and anion is a negative charged Particals. The iodine based contrast increase the attention of x-ray and give contrast differentiation between body tissues.

2) Negative contrast media:- The contrast media , which have low atomic number is called negative contrast media. Ex. air, oxygen, carbon dioxide. It is manly used Gynaecography, Retroperitoneal Pneumography, air encephalography, diagnostic pneumoperitoneum.

Properties Of Contrast Media.

A) Osmolality :- The 3rd generation of contrast media ( ionic dimers and nonionic monomers ) have about 50% of osmolality. But in 4th generation ( nonionic dimers) have 25% of osmolality.

B) Viscosity

C) Toxicity

D) maximum opacity of x-ray.

E) Biological effect.

F) should be safe.

Route Of Introducing The Contrast Media In Patient Body.

A) Intravenous:– The iodinated contrast media are introducing manly cubital vain during special procedure like IVP .

B) ORAL:- The barium sulphate is introducing in oral of patients body for study of upper gastrointestinal tract and iodine contrast also introducing at orally.

C) Rectal:– The barium sulphate also introducing the rectally to study of large intestine and the air water or some time iodine contrast also introducing rectally.

D) Intra Athecal:- The iodinated contrast media are given in the subarachnoid space during myelography, CT cisternography .

E) Intra Ductal:- The iodinated contrast media are directly introducing duct to study of sialography., Dacrocystography.

F) Intra Arterial:- Intra arterial, the iodinated contrast media are directly introducing to the artery during angiography. This is the conventional method to perform the angiography.

Reaction Of Contrast Media

The following reaction are may be occurs during introducing the contrast media.

A) Mild reaction:- in mild reaction, it is generally physiology change in our body. This types of reactions are not needed to treatment. Eg.

– Nausea

– Vomiting

– Itching on skin

– Sneezing

– Warmth

– Headache, Dizziness and shaking

B) Moderate reaction:– In moderate reaction, it is not a life theatening but it may needed to treatment. Eg

– Severe skin rash.

– Blood pressure high.

– Shortness of breath

– Pulmonary edema

– Laryngeal edema

– Trachycardia.

C) Severe reaction:- in Severe reaction, the patient should needed to treatment and hospitalisation. It is very rare reaction. eg.

– Low blood pressure.

– Difficulty in breathing.

– Swelling in throat

– Cardiopulmonary edema.

 Contraindications to the administration of intravascular contrast Media

• Patient refuses to receive intravascular contrast material.

• Patient did not receive premedication, when indicated, prior to scheduled contrast administration.

• Patient has renal insufficiency.

• Patient has thyroid disease that will be treated with systemic 131I radiotherapy. This contraindication applies for iodinated, not gadolinium-based, contrast material only. The reason is that iodinated contrast material transiently decreases 131I radiotracer uptake in the thyroid gland, potentially decreasing the effectiveness of subsequent radioiodide therapy.

• Patient is pregnant. This contraindication particularly applies for the intravascular administration of gadoliniumbased contrast material.

 factors require assessment of patient renal function prior to administration of intravascular contrast material.

• Patient age >60

• History of renal disease, including:

• Dialysis

• Renal transplant

• Single kidney

• Renal cancer

• Renal surgery

• History of hypertension requiring medical therapy

• History of diabetes mellitus:-  Metformin or metformin-containing drug combinations (for iodinated contrast material administration only) At our institution, when the serum creatinine level is ≤1.4 mg/dL, iodinated contrast material can be administered, assuming that there are no other contraindications. When the serum creatinine level is between 1.5 and 1.9 mg/dL or rising, iodinated contrast material can still be administered, but only after a conversation with the referring physician has taken place to discuss the risks and benefits of administering contrast material and possible diagnostic test alternatives. When the serum creatinine level is ≥2.0 mg/dL, iodinated contrast material is generally not administered unless there is an urgent medical necessity.

FAQs.

Q. Is intravascular contrast material safe for use in women who are breast-feeding?

Yes. Less than 1% of administered iodinated contrast material or gadolinium based contrast material is excreted in breast milk, and <1% of the contrast material ingested by infants through breast-feeding is absorbed through the gastrointestinal tract. Furthermore, direct toxicity or allergic sensitization or reaction in infants to absorbed contrast material has not been reported. If the mother has concerns about any potential ill effects to her infant, she may express and discard breast milk for 12 to 24 hours after having received contrast material. In anticipation of this, the mother may use a breast pump to obtain and save breast milk during the 24 hours prior to receiving contrast material.

Q. What major types of enteric contrast agent are available?

Barium sulfate enteric contrast agents (predominantly used in gastrointestinal fluoroscopic and CT studies) are utilized for distention and opacification of the gastrointestinal tract and may be administered by mouth, per rectum, via an ostomy, or via an indwelling bowel catheter. Iodinated enteric contrast agents can alternatively be utilized to distend and opacify the bowel.

Q. What are the major complications of barium sulfate enteric contrast material?

Leakage of barium sulfate enteric contrast material from the bowel into the mediastinum or peritoneal cavity can lead to mediastinitis or peritonitis, respectively. As such, when bowel perforation is suspected or known to exist, iodinated water-soluble enteric contrast material, rather than barium sulfate enteric contrast material, is administered.

Aspiration of large volumes of barium sulfate contrast material can lead to acute respiratory distress or pneumonia. Adverse reactions to barium sulfate enteric contrast material can occur but are rare and are almost always mild.

Q. What are the major complications of iodinated contrast material when used as an oral contrast agent?

Aspiration of high-osmolality iodinated oral contrast material can lead to life-threatening pulmonary edema. As such, in patients at high risk for aspiration, this can be mitigated or prevented by use of low or iso-osmolal iodinated oral contrast material or by use of barium sulfate enteric contrast material. Approximately 1% to 2% of iodinated enteric contrast material is absorbed and subsequently excreted into the urinary tract. Adverse reactions to iodinated enteric contrast material are rare but can be moderate or severe, particularly in patients with a history of prior reaction to intravascular contrast material, as well as in those with active inflammatory bowel disease, where there may be increased enteric absorption of contrast material.

Q. When do adverse reactions to intravascular iodinated contrast material usually occur?

Most reactions to intravascular iodinated contrast occur within 1 hour of intravenous administration. However, delayed adverse reactions may occasionally occur between 1 hour and 1 week following contrast administration. Such delayed reactions are seen more commonly in young adults, women, and patients with a history of allergy, are most commonly cutaneous (e.g., urticaria, rash, or angioedema), and are typically mild to moderate in severity and self-limited. The incidence of delayed allergic-like reactions has been reported to range from 0.5% to 14% and may occur more commonly with iso-osmolal dimeric contrast agents.

Q. When is premedication indicated prior to contrast administration?

The primary indication for premedication prior to contrast-enhanced imaging is the pretreatment of patients at increased risk for an acute allergic-like reaction to contrast material. Premedication generally involves the administration of corticosteroids, sometimes in conjunction with H1 blockers.

At our institution, indications for premedication include:

• Prior moderate or severe allergic-like reaction to contrast material.
• Prior intravenous contrast reaction requiring administration of epinephrine.
• Prior life-threatening reaction to any allergen or medication.
• Presence of asthma with active wheezing.
• Presence of asthma requiring intubation in the last 3 months.

Q. What is iodine “mumps”?

Iodine “mumps” is Sialoadenopathy or salivary gland swelling that may rarely occur in delayed fashion following iodinated contrast administration.

Q. What is a breakthrough reaction?

A breakthrough reaction is a repeat contrast reaction that occurs in a premedicated patient. Breakthrough reactions are most often similar to the index reaction in terms of severity and clinical presentation. Presence of severe allergies to any other substance, more than four allergies, any drug allergy, and chronic use of oral corticosteroids are associated with a higher risk of a moderate or severe breakthrough reaction.

Q. Is there a specific association between presence of a shellfish allergy and an increased allergy to iodinated contrast material?

It is an incorrectly held perception in clinical practice that shellfish allergy specially predisposes patients to contrast reaction. An allergy to shellfish does not increase the risk for an adverse reaction to iodinated contrast material any more than do other allergies.

Q. What is contrast media in radiology?

Contrast media are substances used in medical imaging to enhance the visibility of certain tissues or structures within the body.

Q. Why is contrast media used in radiology?

Contrast media improve the visualization of specific areas or organs, making it easier to diagnose and evaluate medical conditions.

Q. What are the main types of contrast media?

The main types are iodinated contrast media and gadolinium-based contrast media.

Q. How does iodinated contrast media work?

Iodinated contrast media contain iodine, which absorbs X-rays and enhances the visibility of blood vessels and organs.

Q. When is gadolinium-based contrast media used?

Gadolinium-based contrast media are primarily used in MRI scans to improve tissue differentiation.

Q. Are contrast media safe to use?

Contrast media are generally safe, but they can have risks and side effects. Your healthcare provider will assess the risks versus benefits.

Q. What are the common side effects of contrast media?

Common side effects include a warm sensation, metallic taste, and mild allergic reactions like hives.

Q. What is a contrast reaction?

A contrast reaction is an adverse response to the administration of contrast media, which can range from mild to severe.

Q. How are contrast reactions managed?

Treatment of contrast reactions depends on their severity but may involve medications like antihistamines or epinephrine.

Q. Can I have an allergic reaction to contrast media?

-Yes, some individuals may be allergic to contrast media. Allergies should be discussed with your healthcare provider before the procedure.

Q. What is contrast-induced nephropathy?

Contrast-induced nephropathy is kidney damage that can occur after the administration of iodinated contrast media, especially in people with kidney issues.

Q. How can the risk of contrast-induced nephropathy be reduced?

Hydration and adjusting the contrast media dose can help reduce the risk of kidney damage.

Q. Can pregnant women have contrast-enhanced imaging?

Pregnant women should avoid contrast media unless the benefits clearly outweigh the risks.

Q. How long does it take for contrast media to be eliminated from the body?

The elimination time varies depending on the type of contrast media, but it is usually excreted within a few hours to a few days.

Q. What is a contrast-enhanced CT scan?

A contrast-enhanced CT scan involves the use of iodinated contrast media to improve the clarity of CT images.

Q. Are there alternatives to iodinated contrast media?

In some cases, non-contrast MRI or CT scans may be used as alternatives to avoid iodinated contrast.

Q. Can children have contrast-enhanced imaging?

Yes, children can have contrast-enhanced imaging, but the procedure’s appropriateness depends on their specific medical condition.

Q. How is contrast media administered for imaging?

Contrast media can be administered orally, intravenously, or directly into a body cavity, depending on the imaging procedure.

Q. Can contrast media be used in emergency situations?

Yes, contrast media can be used in emergencies to quickly diagnose critical conditions.

Q. What is the cost of a contrast-enhanced imaging procedure?

The cost varies depending on the type of procedure, location, and healthcare provider. Check with your insurance company for coverage details.

Q. What should I tell my healthcare provider before a contrast-enhanced procedure?

Inform your provider of any allergies, medical conditions, medications, and past reactions to contrast media.

Q. Is fasting required before a contrast-enhanced exam?

Fasting may be necessary for certain exams, so follow your healthcare provider’s instructions.

Q. Can I drive home after a contrast-enhanced procedure?

In most cases, you can drive home, but it’s wise to have someone accompany you, especially if you experience side effects.

Q. Can I breastfeed after receiving contrast media?

It’s usually safe to breastfeed after contrast media administration, but consult your healthcare provider for specific guidance.

Q. What happens if I miss my contrast-enhanced imaging appointment?

Contact your healthcare provider to reschedule as soon as possible.

Q. Are there any dietary restrictions after contrast-enhanced imaging?

Your healthcare provider may recommend staying hydrated and avoiding certain foods or drinks temporarily.

Q. What is a contrast-enhanced ultrasound?

Contrast-enhanced ultrasound involves the use of microbubble contrast agents to enhance the visualization of blood flow.

Q. Can I exercise after a contrast-enhanced procedure?

Light exercise is generally fine, but consult your healthcare provider for specific post-procedure instructions.

Q. Are there age limits for contrast-enhanced imaging?

Age alone does not determine eligibility; the appropriateness of the procedure depends on the individual’s medical condition.

Q. Can contrast media be used for interventional procedures?

Yes, contrast media are often used during interventional radiology procedures to guide treatments and surgeries.

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