Off-resonance angiography: a new method to depict vessels--phantom and rabbit studies.
OBJECTIVE
To evaluate the utility of inversion recovery with on-resonant water suppression (IRON) in combination with injection of the long-circulating monocrystalline iron oxide nanoparticle (MION)-47 for contrast material-enhanced magnetic resonance (MR) angiography.


METHODS
Experiments were approved by the institutional animal care committee. Eleven rabbits were imaged at baseline before injection of a contrast agent and then serially 5-30 minutes, 2 hours, 1 day, and 3 days after a single intravenous bolus injection of 80 micromol of MION-47 per kilogram of body weight (n = 6) or 250 micromol/kg MION-47 (n = 5). Conventional T1-weighted MR angiography and IRON MR angiography were performed on a clinical 3.0-T imager. Signal-to-noise and contrast-to-noise ratios were measured in the aorta of rabbits in vivo. Venous blood was obtained from the rabbits before and after MION-47 injection for use in phantom studies.


RESULTS
In vitro blood that contained MION-47 appeared signal attenuated on T1-weighted angiograms, while characteristic signal-enhanced dipolar fields were observed on IRON angiograms. In vivo, the vessel lumen was signal attenuated on T1-weighted MR angiograms after MION-47 injection, while IRON supported high intravascular contrast by simultaneously providing positive signal within the vessels and suppressing background tissue (mean contrast-to-noise ratio, 61.9 +/- 12.4 [standard deviation] after injection vs 1.1 +/- 0.4 at baseline, P < .001). Contrast-to-noise ratio was higher on IRON MR angiograms than on conventional T1-weighted MR angiograms (9.0 +/- 2.5, P < .001 vs IRON MR angiography) and persisted up to 24 hours after MION-47 injection (76.2 +/- 15.9, P < .001 vs baseline).


CONCLUSIONS
IRON MR angiography in conjunction with superparamagnetic nanoparticle administration provides high intravascular contrast over a long time and without the need for image subtraction.
Korosoglou
Grigorios
G
Russell H. Morgan Department of Radiology and Radiological Science, Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
Shah
Saurabh
S
Vonken
Evert-Jan
EJ
Gilson
Wesley D
WD
Schär
Michael
M
Tang
Lijun
L
Kraitchman
Dara L
DL
Boston
Raymond C
RC
Sosnovik
David E
DE
Weiss
Robert G
RG
Weissleder
Ralph
R
Stuber
Matthias
M
D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage; D052203:Ferrosoferric Oxide / Q000008:administration & dosage; D018810:Magnetic Resonance Angiography / Q000379:methods*; D053758:Nanoparticles / Q000008:administration & dosage; D019047:Phantoms, Imaging; D011817:Rabbits; D012044:Regression Analysis
D003287:Contrast Media; C499827:monocrystalline iron oxide nanoparticle; D052203:Ferrosoferric Oxide
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