Spoiling without additional gradients: Radial FLASH MRI with randomized radiofrequency phases

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Pulse Sequence Design
• Biophysics

Background:

• Radial fast low angle shot (FLASH) sequences are crucial for real-time MRI.
• Minimizing repetition times (TR) is essential for high-speed imaging.
• Spoiling transverse magnetizations is necessary to prevent image artifacts.

Purpose of the Study:

• To develop a gradient-free method for spoiling transverse magnetizations in radial FLASH MRI.
• To reduce repetition times (TR) for faster imaging acquisition.
• To enhance the efficiency of radial FLASH MRI sequences.

Main Methods:

• Analysis of residual transverse magnetizations and artifacts in radial gradient echo sequences.
• Comparison of constant and randomized RF phases against conventional RF spoiling (gold standard).
• Assessment of spoiling performance using numerical simulations, phantom experiments, and in vivo human brain MRI.

Main Results:

• Randomized RF phases demonstrate highly efficient spoiling in radial FLASH sequences without gradient rewinding or spoiler gradients.
• Spoiling performance is significantly dependent on the radial trajectory, with interleaved multiturn schemes showing excellent results.
• Simulations, phantom, and in vivo data confirm the effectiveness of the proposed method.

Conclusions:

• Randomized RF phases provide effective spoiling of transverse magnetizations in radial FLASH MRI, eliminating the need for additional spoiler gradients.
• This technique facilitates shorter repetition times, crucial for high-speed real-time MRI applications.
• The findings offer a pathway to improved efficiency and speed in MRI acquisition.