Chapter 5 Contrast Media Flashcards
(50 cards)
What are the two types of radiographic contrast media?
Positive and negative contrast media
Positive contrast media increase radiographic opacity, while negative contrast media reduce it.
What is an example of positive contrast media?
Barium (Z=56) and iodine (Z=53)
Positive contrast media increase absorption of x-ray photons.
What is the K-absorption edge (K-edge) effect?
An abrupt increase in photoelectric absorption when x-ray beam energy is beyond the binding energy of inner k-shell electrons.
This effect is utilized to enhance contrast in imaging.
What is an example of negative contrast media?
Room air, CO2, NO2
Negative contrast media reduce the absorption of x-ray photons.
What is the primary formulation of barium used in veterinary medicine?
Micro-pulverised liquid barium preparations
Barium sulfate is commonly used in GI contrast studies.
What is the purpose of emulsifiers, stabilizers, and dispersants in barium preparations?
To maintain barium in suspension
This ensures even distribution in the barium-water mixture.
What concentration expressions are used for barium sulfate suspension?
Weight/volume (w/v) and weight/weight (w/w)
These expressions indicate the percentage of barium sulfate in relation to the final product.
What are potential adverse effects of barium leakage?
Mediastinitis, peritonitis/septic peritonitis, fibrinous adhesions, granulomatous nodules
Leakage can occur from GI perforation.
What is recommended if GI perforation is of concern?
An iodinated, nonionic, water-soluble contrast medium
This is safer in cases of potential perforation.
What can aspiration of barium lead to?
Pneumonia and acute respiratory distress
Large volumes of aspirated barium can cause severe respiratory issues.
What are the two main classifications of iodine-based contrast media?
Water-soluble and water-insoluble
Water-soluble media are primarily used in clinical practice.
What is the most common route of administration for iodinated contrast media?
IV administration
Other routes include oral, rectal, injection into the urinary system, or intrathecal injection.
How does protein binding affect the excretion of iodinated contrast media?
Higher protein binding leads to longer plasma retention and less renal excretion
This can result in more biliary excretion.
What is the difference between ionic and nonionic contrast media?
Ionic media dissociate into ions; nonionic media do not
Nonionic media have a higher solubility due to polar hydroxyl groups.
What is the osmolality of contrast media expressed as?
Milliosmole per kilogram of water (mOsm/kg water)
Osmolality is influenced by the number of independent particles in solution.
What is the effect of higher osmolality in contrast media?
Increased adverse reactions
High-osmolality media draw fluid into the bowel, diluting the contrast.
What does the contrast ratio represent?
The number of iodine atoms per number of particles in solution (I/P ratio)
A higher I/P ratio implies greater opacity.
What is the effect of viscosity on contrast media?
High viscosity can complicate injection
Viscosity is inversely affected by factors that improve solubility and hydrophilicity.
What is the only available water-insoluble contrast medium?
Ethiodized oil medium (Lipiodol)
It is used in embolization solutions during interventional radiology.
What are acute and delayed adverse reactions to iodinated contrast media?
Acute: within 1 hour; Delayed: within hours to 1 week
Acute reactions are often hypersensitivity, while delayed reactions are typically T-cell mediated skin reactions.
What are common mild reactions in humans to iodinated contrast media?
Nausea, vomiting, urticaria
Severe reactions can include bronchospasm and pulmonary edema.
What are two risk factors for hypersensitivity reactions to iodinated contrast media?
Previous reaction to contrast medium and having asthma or severe allergies
These factors increase the likelihood of adverse reactions.
What is contrast-induced acute kidney injury (CI-AKI)?
A sudden decrease in kidney function within 48 hours of IV injection of iodinated contrast medium
CI-AKI can result from various pathophysiological mechanisms.
What are some risk factors for CI-AKI in humans?
Pre-existing renal impairment, dehydration, diabetes, older age
High-osmolar ionic contrast media are associated with greater nephrotoxicity.
