Contrast-enhanced blood-pool MR angiography with optimized iron oxides: effect of size and dose on vascular contrast enhancement in rabbits.
OBJECTIVE
To investigate intravascular enhancement of bolus-injectable small and ultrasmall superparamagnetic iron oxides (USPIOs) of different particle sizes and relaxivities for first-pass and blood-pool magnetic resonance (MR) angiography.


METHODS
Iron oxides with different particle sizes (hydrodynamic diameters, 21, 33, 46, and 65 nm) were bolus injected intravenously at three doses (10, 20, and 40 micromol per kilogram body weight). An extracellular contrast agent (gadopentetate dimeglumine) served as a control. MR angiography was performed multiple times after intravenous injection (5-120 minutes and 24 hours later). Signal enhancement was calculated from signal intensity measurements in the abdominal aorta and renal and iliac arteries.


RESULTS
Highest enhancement was seen during the first pass with all contrast agents. USPIO enhancement in the abdominal aorta increased significantly with decreasing particle size (65 nm vs 33 nm, 65 nm vs 21 nm; P <.01).


CONCLUSIONS
The smallest iron oxide provided signal enhancement comparable with that of gadopentetate dimeglumine at 40 micromol iron per kilogram for first-pass investigations, with prolonged signal enhancement up to 25 minutes, allowing multiple measurements after injection of a single bolus.
Allkemper
Thomas
T
Department of Clinical Radiology, University Hospital Münster, Albert-Schweitzer-Strasse 33, 48129 Münster, Germany.
Bremer
Christoph
C
Matuszewski
Lars
L
Ebert
Wolfgang
W
Reimer
Peter
P
D000704:Analysis of Variance; D000818:Animals; D001012:Aorta, Abdominal / Q000033:anatomy & histology; D003287:Contrast Media; D007083:Iliac Artery / Q000033:anatomy & histology; D007089:Image Enhancement / Q000379:methods; D007275:Injections, Intravenous; D007501:Iron / Q000008:administration & dosage*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D010087:Oxides / Q000008:administration & dosage*; D010316:Particle Size; D011817:Rabbits; D012077:Renal Artery / Q000033:anatomy & histology
D003287:Contrast Media; D010087:Oxides; D007501:Iron