1.

Overview, advantages, and limitations of the imaging techniques routinely used in nanomedicine research

Technique	Nanoparticles	Depth	Advantage	Limitation
PET/SPECT	Radio-labeled nanoparticles	No limit	Noninvasiveness and high sensitivity	Exposure to ionizing radiation and relatively low spatial resolution
CT	Gold, silver, and iodine nanoparticles	No limit	Noninvasiveness and high contrast resolution	Relatively high dose of ionizing radiation, limited soft tissue resolution, and exposure to ionizing radiation
MRI	Iron oxide nanoparticles, cobalt ferrites, and Gd 3+-labeled nanoparticles	No limit	Noninvasiveness and high spatial resolution	Relatively low sensitivity
Optical	Quantum dots	<1 cm	Noninvasiveness, and no harmful effect by nonionizing radiation	Relatively low spatial resolution
Ultrasound	Silica, nanobubble	Millimeters to centimeters	Noninvasiveness, real time, low cost, and no harmful effect by nonionizing radiation	Limited spatial resolution and unsuitable for examination of digestive organs and bone