MR angiography with an ultrasmall superparamagnetic iron oxide blood pool agent.
The purpose of the study was to investigate the use of a dextran-coated ultrasmall superparamagnetic iron oxide (USPIO) as a blood pool contrast agent for thoracic and abdominal MR angiography. Abdominal and thoracic MR angiography was performed in six healthy volunteers using two-dimensional and three-dimensional spoiled gradient echo (SPGR) sequences before and after intravenous administration of USPIO. Doses ranged from 1.1 to 2.6 mg Fe/kg. Flip angle was varied from 20 to 60 degrees. Subjective image quality, analysis of signal-to-noise ratio (SNR), and blood T1 relaxation times were measured. USPIO significantly lowered the T1 of blood (from 1,210 ms precontrast to 159 ms postcontrast at a dose of 2.6 mg Fe/kg) (P < .01). Image quality on coronal fast three-dimensional breath-hold SPGR images of the abdomen increased with increasing dose and was maximum at the highest dose, producing an aortic SNR of 9.6 compared to 1.8 precontrast. Axial two-dimensional time-of-flight (TOF) aortic SNR was reduced significantly from 13 on precontrast to 6 on the postcontrast images at the highest dose (P < .05) due to T2* shortening effects. There was little flip angle dependence on image quality. Due to the T1 shortening effect and long intravascular half-life, USPIO improved visualization of vascular anatomy using three-dimensional fast SPGR imaging. The echo time must be minimized to minimize signal loss from T2* shortening effects. The blood pool distribution of USPIO is useful for equilibrium-phase MR angiography.
Anzai
Y
Y
Department of Radiology, University of Michigan School of Medicine, Ann Arbor 48109-0030, USA.
Prince
M R
MR
Chenevert
T L
TL
Maki
J H
JH
Londy
F
F
London
M
M
McLachlan
S J
SJ
D000005:Abdomen / Q000098:blood supply*; D000328:Adult; D000792:Angiography; D003287:Contrast Media; D004305:Dose-Response Relationship, Drug; D005240:Feasibility Studies; D005260:Female; D005290:Ferric Compounds / Q000008:administration & dosage / Q000493:pharmacokinetics; D006207:Half-Life; D006801:Humans; D007275:Injections, Intravenous; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010690:Phlebography; D012016:Reference Values; D012680:Sensitivity and Specificity; D013909:Thorax / Q000098:blood supply*
D003287:Contrast Media; D005290:Ferric Compounds; C000499:ferric oxide