Improved in-stent magnetic resonance angiography with high flip angle excitation.
OBJECTIVE
To optimize the intraluminal signal intensity of a nitinol stent by performing contrast-enhanced three-dimensional magnetic resonance angiography (CE-MRA) with varying flip angles (FAs).


METHODS
Contrast-enhanced magnetic resonance angiography at 1.5 T and FAs of 30 degrees, 100 degrees, and 150 degrees was performed on five sheep with 10 iliac nitinol stents (Memotherm-FLEXX). Maximum-intensity projections (MIPs) and composite images of MIPs were performed and compared.


RESULTS
Reconstructed MIPs at an FA of 150 degrees showed a slightly disturbed lumen visibility inside the stent accompanied by low-grade lumen visibility outside the stent and vice versa for an FA of 30 degrees. Composite images of a 30 degrees MIP added to a 150 degrees MIP resulted in improved image quality compared with the standard MIP of a single FA.


CONCLUSIONS
Signal loss due to radiofrequency shielding inside nitinol stents imaged by CE-MRA can be reduced by applying high FAs. Composite MIP images allow simultaneous visualization of the lumen inside as well as outside the stent.
Meyer
J M
JM
Department of Diagnostic Radiology, University of Technology Aachen, Pauwelsstrasse 30, Aachen, D-52074, Germany. meyer@rad.rwth-aachen.de
Buecker
A
A
Spuentrup
E
E
Schuermann
K
K
Huetten
M
M
Hilgers
R D
RD
van Vaals
J J
JJ
Guenther
R W
RW
D000497:Alloys; D000818:Animals; D003287:Contrast Media; D019786:Gadolinium DTPA; D007083:Iliac Artery / Q000473:pathology / Q000601:surgery; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D012756:Sheep; D015607:Stents
D000497:Alloys; D003287:Contrast Media; C013616:nitinol; D019786:Gadolinium DTPA