Evaluation of in-stent stenosis by magnetic resonance phase-velocity mapping in nickel-titanium stents.
OBJECTIVE
To evaluate different grades of in-stent stenosis in a nickel-titanium stent with MRI.


METHODS
Magnetic resonance phase velocity mapping (MR-PVM) was used to measure flow velocity through a 9-mm NiTi stent with three different degrees of stenosis in a phantom study. The tested stenotic geometries were 1) axisymmetric 75%, 2) axisymmetric 90%, and 3) asymmetric 50%. The MR-PVM data were subsequently compared with the velocities from computational fluid dynamic (CFD) simulations of identical conditions.


RESULTS
Good quantitative agreement in velocity distribution for the 50% and 75% stenoses was observed. The agreement was poor for the 90% stenosis, most likely due to turbulence and the high-velocity gradients found in the small luminal area relative to the pixel resolution in our imaging settings.


CONCLUSIONS
The accuracy of the MRI velocities inside the stented area renders MRI a modality that may be used to assess moderate to severe in-stent restenosis (ISR) in medium-sized vascular stents in peripheral vessels, such as the iliac, carotid, and femoral arteries. Advances in MR instrumentation may provide sufficient resolution to obtain adequate velocity information from smaller vessels, such as the coronary arteries, and allow MRI to substitute for invasive and expensive catheterization procedures currently in clinical use.
Holton
Andrea D
AD
Department of Biomedical Engineering, University of Alabama at Birmingham, 1075 13th Street South, Birmingham, AL 35294-4440, USA.
Walsh
Edward G
EG
Brott
Brigitta C
BC
Venugopalan
Ramakrishna
R
Hershey
Bradley
B
Ito
Yasushi
Y
Shih
Alan
A
Koomullil
Roy
R
Anayiotos
Andreas S
AS
D003251:Constriction, Pathologic / Q000175:diagnosis; D003326:Coronary Circulation / Q000502:physiology; D004868:Equipment Failure; D019544:Equipment Failure Analysis; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine; D008953:Models, Anatomic; D009532:Nickel; D019047:Phantoms, Imaging; D011673:Pulsatile Flow; D012680:Sensitivity and Specificity; D015607:Stents / Q000009:adverse effects*; D014025:Titanium; D014655:Vascular Resistance
C040654:titanium nickelide; D009532:Nickel; D014025:Titanium