Neurointervention.  2011 Aug;6(2):71-77. 10.5469/neuroint.2011.6.2.71.

Optimization of MR Parameters of 3D TOF-MRA for Various Intracranial Stents at 3.0T MRI

• Choi JW
• Roh HG
• Moon WJ
• Chun YI
• Kang CH

• KMID: 1783986
• DOI: http://doi.org/10.5469/neuroint.2011.6.2.71

Abstract

PURPOSE
The in-stent signal reduction of the stented artery caused by susceptibility artifact or radiofrequency shielding artifact limited the use of time-of-flight MR angiography (TOF-MRA) as a follow-up tool after intracranial stenting. We showed the degree of an artifact according to different stent types, and optimized MR parameters for TOF-MRA in patients with intracranial stent on 3.0 T MRI.
MATERIALS AND METHODS
Four stents (Neuroform, Wingspan, Solitaire, and Enterprise) were placed in a vascular flow phantom and imaged by changing flip angle (FA; 20degrees,30degrees,40degrees,50degrees and 60degrees) and bandwidth (BW; 31, 42 and 62.5 KHz) using TOF-MRA. Source data of each image set with different FA and BW were reconstructed with the maximal intensity projection (MIP) technique, and MIP images were used to evaluate the in-stent signal reduction of each stent according to the change of MR parameters. The in-stent signal reduction was assessed by calculating the relative in-stent signal (RIS) inside the stent as compared with background and signal intensity of the tube outside the stent. The optimal FA and BW of each stent were determined by comparing the RIS in each stent by one-sample t test. Finally, one neuroradiologist chose one image set with the best image quality.
RESULTS
The mean RIS for Neuroform, Wingspan, Solitaire and Enterprise stent was 66.3 +/- 6.0, 44.2 +/- 5.8, 22.8 +/- 3.3 and 8.2 +/- 2.9, respectively. The significantly high RIS of each stent was obtained with FA/BW value of 20degrees/31 KHz (Neuroform), 20degrees/31 KHz and 30degrees/42 KHz (Wingspan), 40degrees/42 KHz and 50degrees/31 KHz (Solitaire) and 40degrees/31 KHz and 50degrees/31 KHz (Enterprise). Among these MIP images with significantly high RIS, images with FA/BW value of 20degrees/31 KHz (Neuroform and Wingspan) and 50degrees/31 KHz (Solitaire and Enterprise) had the best image quality.
CONCLUSION
The degree of artifact was variable according to the design of each intracranial stent. The luminal visualization of closed-cell design stents such as Solitaire and Enterprise can be improved by higher FA. Thus, MR parameter should be adjusted according to the type of intracranial stents.

Keyword

Magnetic resonance imaging; Magnetic resonance angiography; Artifacts; Stents

MeSH Terms

Angiography
Arteries
Artifacts
Follow-Up Studies
Humans
Magnetic Resonance Angiography
Magnetic Resonance Imaging
Phenobarbital
Stents
Phenobarbital

Figure

• 

  Fig. 1 Relative In-stent Signal According to the Change of FA.Bars represent RIS for each stent according to the change of FA at BW of 31 KHz. The number in the boxes means RIS value for each stent.

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  Fig. 2 Mean Relative In-stent Signal According to the Change of Bandwidth.Bars represent mean RIS (mean of RIS at FA of 30° and 40°) for each stent according to the change of BW. The number in the boxes means mean RIS value for each stent.

• 

  Fig. 3 MIP images of the each stent with significantly high RIS. MIP images of Neuroform (A, FA/BW; 20°/31 KHz), Wingspan (B.1, FA/BW; 20°/31 KHz, and B.2, FA/BW; 30°/42 KHz), Solitaire (C.1, FA/BW; 40°/42 KHz, and C.2, FA/BW; 50°/31 KHz) and Enterprise (D.1, FA/BW; 40°/31 KHz, and D.2, FA/BW; 50°/31 KHz). A band-like artifact (arrowhead) is visible at the end of the each stent due to platinum marker. A complete signal loss of the lumen (arrow) near the proximal marker of the Solitaire stent was shown.

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