This chapter reviews new blood pool agents and studies performed to evaluat
e them. The major differences between a variety of blood pool agents are id
entified. These agents include large gadolinium (Gd)-labeled polymers, ultr
asmall superparamagnetic particles of iron oxide (USPIO), and MS-325, a sma
ll Gd chelate that binds to serum albumin (HAS). The chapter also outlines
some early phase I trials on normal human subjects.