Variable-density velocity-selective magnetization preparation for non-contrast-enhanced peripheral MR angiography

Area of Science:

• Magnetic Resonance Imaging
• Medical Imaging Physics
• Cardiovascular Imaging

Background:

• Velocity-selective (VS) magnetization preparation is a promising technique for non-contrast-enhanced magnetic resonance angiography (NCE-MRA).
• Conventional VS-MRA methods suffer from aliased saturation, leading to signal loss in arteries.
• This signal loss, related to the velocity field-of-view (vFOV), can compromise diagnostic accuracy.

Purpose of the Study:

• To develop an improved VS preparation pulse sequence to overcome aliased saturation issues in NCE-MRA.
• To enhance arterial signal and reduce signal loss compared to existing VS-MRA techniques.
• To optimize k-space sampling for improved velocity encoding and signal uniformity.

Main Methods:

• Developed a novel VS preparation sequence utilizing non-uniform k-space sampling.
• Employed a variable density sampling strategy to diffuse aliased excitation over velocity.
• Optimized the sampling function to maximize signal in the velocity passband and minimize variance.
• Validated the method using Bloch simulations and in-vivo peripheral NCE-MRA in healthy subjects.

Main Results:

• The proposed variable density VS-MRA significantly reduced arterial signal loss compared to conventional methods.
• Demonstrated a higher arterial signal-to-noise ratio (58.50 ± 14.29 vs. 55.54 ± 12.32; p < 0.05).
• Achieved improved artery-to-background contrast-to-noise ratio (22.75 ± 7.57 vs. 20.60 ± 6.51; p < 0.05).

Conclusions:

• The novel variable density VS preparation effectively mitigates aliased saturation in NCE-MRA.
• This technique offers superior image quality by preserving arterial signal.
• The optimized sequence holds potential for enhanced non-contrast angiography applications.