The industry standard of computed tomography (CT) contrast media power injectors changed over time from single-head to dual-head systems. The advantage of a power (or pressure) injector with two syringes is that a saline solution can be injected first to open the veins, followed by a second injection with contrast agent. Then the first head flushes the saline to maintain contrast flow. As a result, much less contrast agent is needed (about 30 percent less), helping to reduce costs. Dual-head contrast media injectors also provide greater patient safety by reducing the pressure of the flow rate, helping to prevent damage to the veins.
Contrast delivery is much more controlled and efficient when using a dual-head power injector (also called double-piston injector). Also, these medical devices are required to accommodate the quick imaging times typical for a multi-detector CT scanner.

See also Contrast Media Injector, Single-Head CT Power Injector, CT Power Injector, Multi-Head Contrast Media Injector, Syringeless CT Power Injector.

An embolization can occur by movement of a blood clot, piece of tissue, or pocket of air or gas through the bloodstream until it stops in place, cutting off the flow of blood.
An embolization during a medical procedure is the insertion of material such as gelatin sponge or metal coils through a catheter into a blood vessel to stop hemorrhaging, excessive bleeding or cut off blood flowing to a tumor or arteriovenous malformation.

Ischemia refers to a lack of adequate blood flow to an organ, such as the heart or the brain, which may be the result of a blood clot, blood vessel constriction or a hemorrhage.

See also Regional Cerebral Blood Flow, Blood Brain Barrier, Cerebral Blood Pool Imaging and Hematoma.

Adverse reactions on contrast agents are rare, but like all other pharmaceuticals, contrast media are not completely without side effects.
Adverse effects to contrast media include allergic symptoms, anaphylactoid reactions, chemotoxic reactions, idiosyncratic reactions, contrast-induced nephropathy, iodide-induced hyperthyroidism and local tissue damage. An adverse reaction can be related to dose, the toxicity, and the physio-chemical properties of the contrast agent, for example osmolality, viscosity, and hydrophilicity.
Side effects such as a metallic taste in the mouth, generalized warmth or flushing, nausea and vomiting, increase with rapid flow and large volume of the injected agent. Although venous tolerance is usually good, there have been reports of sensation like burning, stinging or numbness and of venospasm.

Characterization of adverse reactions include:

(A or amp) The SI base unit of electric current.
Definition: Two parallel conductors, infinitely long and having negligible cross section should be placed 1 meter apart in a perfect vacuum. One ampere is the current that creates between them a force of 0.2 µN (micronewton) per meter of length.
One ampere represents a current flow of 1 coulomb of charge per second.
One ampere of current results from a potential distribution of 1 volt per ohm of resistance, or from a power production rate of 1 watt per volt of potential.
The unit is known informally as the amp, but A is its official symbol and is named for the French physicist André-Marie Ampère.
See also System International.