Nanoparticles may become the workhorse of the molecular imaging age. Although each microscopic agent is only about 250 nm in diameter, they pack an amazing punch measured in their high relaxivity rate as an MR contrast agent, high count rates during SPECT imaging, and echogenic properties during sonography.
Lipid-encapsulated liquid perfluorocarbon nanoparticles, developed at Washington University in St. Louis, can carry 500 indium atoms per particle or 50,000 MR-enhancing gadolinium atoms per particle. They can also raise reflexivity of fibrin thrombi in vivo by an order of magnitude of two.
The Nanotechnology Working Group of the National Institute of Health's National Heart, Lung, and Blood Institute recognizes that nanoparticles could have an immediate impact on the diagnosis and treatment of unstable intravascular plaque. Its recommendations, published in December 2003, note that nanoparticle-enhanced MR imaging can identify at-risk patients. The agents can then serve as a delivery vehicle for drugs that are released with focused ultrasound, near-infrared energy, or a magnetic pulse aimed at the thrombus.