Table 1.

Advantages and disadvantages of imaging modalities used with targeted or non-targeted imaging agents.

Modality	Advantages	Disadvantages	Contrast agents	Radiation
CT	Unlimited tissue depth penetration	Radiation exposure	Krypton	X-rays
	High spatial resolution	Poor soft tissue contrast	Xenon
	Can be used for whole body imaging		Iodine
	Low acquisition time		Barium
	Anatomical imaging
Positron emission tomography (PET)	Unlimited tissue depth penetration	Radiation exposure	11C	High energy γ-rays
	Can be used for whole body imaging	Low spatial resolution and long acquisition time	18F
	Detailed anatomical information can be obtained when combined with CT or MRI	Expensive	64Cu
MRI	Unlimited tissue depth penetration	Expensive	Gd 3+	Radio waves
	Non-ionizing radiation	Long acquisition time and limited sensitivity	SPIO, USPIO
	High spatial resolution and excellent soft tissue contrast
	Whole body imaging possible
Ultrasound	High spatial resolution	Cannot be used for whole body imaging	Microbubbles	High frequency sound
	Real time imaging with low acquisition time
	Highly sensitive and inexpensive
OI	High spatial resolution	Cannot be used for whole body imaging limited tissue depth penetration	Fluorescent dyes and molecules Light sensitive NPs	Visible or near-infrared light
	Real time imaging with low acquisition time
	Highly sensitive and inexpensive