, Aspiring pilot, Alaskan. 1  Well, if you want to be a USAF drone pilot, the process is 5+ years, and relatively difficult, the most difficult section being the flight training itself. Manned flight school has a ~30% washout rate, so I assume the drone program is similar.
A bottle of Omniscan contrast agent. MRI contrast agents are a group of contrast media used to improve the visibility of internal body structures in magnetic resonance imaging (MRI). The most commonly used compounds for contrast enhancement are gadolinium-based.
History. The earliest report on contrast agents in ultrasound imaging dates back to 1968. The first investigations used air-filled microbubbles, which were highly unstable, dissolved rapidly in blood and lost their echogenicity; furthermore, significant amounts were filtered by the lungs because of their large diameter.