Contrast Administration (26) Flashcards
Differential attenuation
Basis of CT:
Beam varies based on attenuating property of tissues
Most common contrast agents (2)
Water-soluble Iodine
Barium Sulfate
Only contrast acceptable for IV injection
Water-soluble iodine
Means of detoxifying Iodine
chemical binding to benzene ring
Contrast agents that dissociate into charged particles in water/blood
Ionic Contrast Agents
Osmolarity
measure of osmotic pressure of a solution concerning the number of particles per volume of solution: “the number of particles in a volume of fluid”
Blood/Human Serum Osmolarity (level)
~300 mOsm/L
Impact of osmolarity difference b/w contrast/blood
Damaged/destroyed blood cells
Benefit of Non-ionic Contrast
Lower osmolality–>gen less side effects
The majority of CT contrast media has lower osmolality resulting in
Fewer side effects
Iso-osmolar
Example:
Osmolarity virtually identical to blood
Visipaque 320
Metrizoate (Isopaque 370)
Ionic/2100
Ioxaglate (Hexabrix)
Ionic/580
Iohexol (Omnipaque 350)
Non-ionic/884
Iopamidol (Isovue 370)
Non-ionic/796
Iopromide (Ultravist 370)
Non-ionic/774
Iodixanol (Visipaque 320)
Non-ionic/290
Barium Sulfate (4)
High Z=56 great for GI enhancement
Suspension not water soluble
Enteric only
Barium escaping GI tract must be surgically evacuated
Barium Sulfate: CT vs Fluoro
Concentration much lower in CT (2% vs 40%) d/t high resolution of CT (and –> cause severe artifact)
Osmolality
(Osmotic) concentration of solution:
total solute particles per kg
Osmolarity
Concentration of a solution:
total solute particles per L
The majority of CT contrast media has lower side effects d/t
Lower osmolality
Contrast agents that are more toxic in part because of increased osmolarity
Ionic Contrast Agents
Iopromide
Ultravist 370
