A medical contrast medium (or contrast agent) is a substance used to enhance the contrast of structures or fluids within the body in medical imaging. It is commonly used to enhance the visibility of blood vessels and the gastrointestinal tract.
- 1 Types
- 2 Adverse effects
Several types of contrast media are in use in medical imaging and they can roughly be classified based on the imaging modalities where they are used. Although other types exist, most common contrast agents work based on X-ray attenuation and magnetic resonance signal enhancement.
X-ray attenuation - Main article: Radiocontrast agent
Iodine and barium are the most common types of contrast medium for enhancing x-ray-based imaging methods. Various sorts of iodinated contrast media exist, with variations occurring between the osmolarity, viscosity and absolute iodine content of different media. Non-ionic dimers are favored for their low osmolarity and toxicity, but have a correspondingly higher price attached to their use.
MR signal enhancing - Main article: MRI contrast agent
This would include gadolinium for use in magnetic resonance imaging as a MRI contrast agent. In the 3+ oxidation state the metal has 7 unpaired f electrons. This causes water around the contrast agent to relax quickly, enhancing the quality of the MRI scan.
Ultrasound scattering and frequency shift - Main article: Contrast-enhanced ultrasound
Microbubble contrast agents are used to aid the sonographic examination, specifically echocardiograms, for the detection of a cardiac shunt. These bubbles are composed of agitated saline solution, most of which are too large to pass through the lung capillaries. Therefore, the only ones that reach the left side of the heart pass through an abnormal connection between the two sides of the heart, a so-called right-to-left shunt. In addition, pharmaceutically prepared microbubbles are composed of tiny amounts of nitrogen or perfluorocarbons strengthened and supported by a protein, lipid, or polymer shell. These are small enough to pass through the capillaries and are used to increase the contrast in the left ventricle, improving the visualization of its walls. The drop in density on the interface between the gas in the bubble and the surrounding liquid strongly scatters and reflects the ultrasound back to the probe. This process of backscattering gives the liquid with these bubbles a high signal, which can be seen in the resulting image.
Adverse effects - While modern contrast media are generally safe to use, medical conditions can be caused by the administration of various contrast media. Reactions can range from minor to severe, sometimes resulting in death
with death being about 0.9 per 100,000 cases. To better understand the reactions and to efficiently manage patients at risk, it is useful to classify them. Risk factors for developing severe reactions include strong allergies, bronchial asthma, cardiac disease and beta-blocker use. While the previously suspected IL-2 medication is no risk for the acquisition of adverse events.
Please refer to the drug classes from Drugs.com listed below for further information.
- iodinated contrast media
- ionic iodinated contrast media
- lymphatic staining agents
- magnetic resonance imaging contrast media
- non-iodinated contrast media
- non-ionic iodinated contrast media
- ultrasound contrast media
Contrast Media Websites
Contrast media tutorial - Department of Radiology
Contrast Media & Devices - Mallinckrodt
GE X-Ray Contrast Media - Omnipaque - GE Healthcare India
Diagnostic Imaging Products — Official Website
Diagnostic Imaging Products – Bayer HealthCare
iohexol - Medscape Reference
Manual on Contrast Media v9 - American College
Radiocontrast agent - Wikipedia
Radiocontrast agents | Drugs.com
Thomson, K; Varma, D (2010). "Safe use of radiographic contrast media". Australian Prescriber, 33:19-22. Available at http://www.australianprescriber.com/magazine/33/1/19/22/
USPharmacist.com > Intravenous Radiocontrast Media X-ray contrast media made clear
Web review: Contrast media in radiology and imaging
CREATININE CLEARANCE EQUATIONS
1) CKD-EPI CALCULATOR
2) mdcalc.com | MDRD GFR Equation
3) mdcalc.com | Creatinine Clearance (Cockcroft-Gault Equation)
Contrast Media and the Kidney
1) Contrast media and the kidney: European Society of Urogenital Radiology (ESUR) Guidelines
2) preventing iodinated contrast media induced renal failure - SFR
3) Guidelines on the Administration of Intravenous Iodinated Contrast
4) Manual on Contrast Media v8 - American College of Radiology
Renal Dosing: Drug Prescribing in Renal Failure Nephrology: 3. Safe drug prescribing for patients with renal insufficiency (Click) Drug Dosing Adjustments in Patients with Chronic Kidney Disease (Click)
Drug-Induced Acute Renal Failure (Click) Guidelines for Drug Dosing Regimens in Chronic Kidney Disease (Click)
Drug Therapy in Kidney Disease (Click)
National Kidney Foundation (Click)