Functional magnetic resonance imaging of the kidney using macromolecular contrast agents.
BACKGROUND
Functional magnetic resonance (MR) imaging of the kidney relies on low-molecular-weight contrast agents. These agents are glomerular filtration markers and are neither secreted nor reabsorbed by the tubules but are filtered at the glomerulus. Low-molecular-weight contrast agents provide limited functional information. A new generation of macromolecular magnetic contrast agents is under development for MR angiography. These agents may provide additional renal functional information not provided by low-molecular-weight agents.


METHODS
We review the use of macromolecular contrast agents such as gadolinium-bound albumin (Gd-albumin), gadolinium-bound dendrimer (Gd-dendrimer), and ultrasmall particles of iron oxide (USPIO) in specific renal parenchymal diseases. These data are largely derived from animal studies because many of these agents have not been extensively deployed in human populations.


RESULTS
Different specific uses have been documented for macromolecular contrast agents. Gd-albumin appears to detect the source of proteinuria and localize the site of recurrent proteinuria after transplantation. Gd-dendrimer uptake reflects damage to the proximal straight tubule in the outer medulla. USPIO agents demonstrate sites of inflammatory changes within the kidney.


CONCLUSIONS
Although not yet in widespread clinical use, macromolecular MR contrast agents may play a role in the evaluation of functional diseases of the kidneys.
Choyke
P L
PL
Molecular Imaging Program, National Cancer Institute, Building 10, Room B3B69, Bethesda, MD 20892-1002, USA. pchoyke@nih.gov
Kobayashi
H
H
D000418:Albumins; D003287:Contrast Media / Q000008:administration & dosage*; D050091:Dendrimers; D003911:Dextrans; D052203:Ferrosoferric Oxide; D005682:Gadolinium; D019786:Gadolinium DTPA; D006801:Humans; D007501:Iron; D007668:Kidney / Q000033:anatomy & histology / Q000473:pathology*; D007674:Kidney Diseases / Q000175:diagnosis*; D046911:Macromolecular Substances; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D010087:Oxides
D000418:Albumins; D003287:Contrast Media; D050091:Dendrimers; D003911:Dextrans; D046911:Macromolecular Substances; D058185:Magnetite Nanoparticles; D010087:Oxides; C058946:albumin-(gadolinium-DTPA); C097921:ferumoxtran-10; D005682:Gadolinium; D007501:Iron; D019786:Gadolinium DTPA; D052203:Ferrosoferric Oxide