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Published on: November 20, 2015
Optimization of MR Parameters of 3D TOF-MRA for Various Intracranial Stents at 3.0T MRI
Jin Woo Choi1, Hong Gee Roh, Won-Jin Moon
1Department of Radiology, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Korea.
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; 20°,30°,40°,50° and 60°) 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 20°/31 KHz (Neuroform), 20°/31 KHz and 30°/42 KHz (Wingspan), 40°/42 KHz and 50°/31 KHz (Solitaire) and 40°/31 KHz and 50°/31 KHz (Enterprise). Among these MIP images with significantly high RIS, images with FA/BW value of 20°/31 KHz (Neuroform and Wingspan) and 50°/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.
Insights
Optimizing magnetic resonance imaging (MRI) parameters for time-of-flight MR angiography (TOF-MRA) improves visualization of intracranial stents. Adjusting flip angle and bandwidth based on stent design reduces artifacts, enhancing follow-up imaging after stenting.
Area of Science:
- Medical Imaging
- Neuroradiology
- Biomedical Engineering
Background:
- Susceptibility and radiofrequency shielding artifacts in time-of-flight MR angiography (TOF-MRA) limit intracranial stent visualization.
- Artifacts hinder the use of TOF-MRA for post-intracranial stenting follow-up.
- Stent design significantly influences artifact severity and signal reduction.
Purpose of the Study:
- To evaluate artifact degree across different intracranial stent types.
- To optimize magnetic resonance (MR) parameters for TOF-MRA in patients with intracranial stents.
- To improve luminal visualization of stented intracranial arteries on 3.0 T MRI.
Main Methods:
- Four intracranial stents (Neuroform, Wingspan, Solitaire, Enterprise) were tested in a vascular flow phantom.
- Time-of-flight MR angiography (TOF-MRA) was performed varying flip angle (FA) and bandwidth (BW).
- Relative in-stent signal (RIS) was calculated to assess signal reduction; optimal parameters were determined using statistical analysis.
Main Results:
- Significant in-stent signal reduction varied by stent type, with Enterprise showing the least signal (8.2 ± 2.9).
- Optimal FA/BW combinations were identified for each stent to maximize signal.
- Best image quality was achieved with specific FA/BW settings: 20°/31 KHz for Neuroform/Wingspan and 50°/31 KHz for Solitaire/Enterprise.
Conclusions:
- Intracranial stent artifact severity is dependent on stent design.
- Higher flip angles can improve luminal visualization for closed-cell stents (Solitaire, Enterprise).
- Tailoring MR parameters to specific stent types is crucial for effective TOF-MRA follow-up.
