Fully refocused gradient recalled echo (FRGRE): factors affecting flow and motion sensitivity in cardiac MRI

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Cardiovascular Imaging
• Pulse Sequence Optimization

Background:

• The Fully Refocused Gradient Recalled Echo (FRGRE) sequence, also known as True FISP, is utilized in cardiac MRI.
• Previous implementations required optimization for improved image quality in cardiac applications.

Purpose of the Study:

• To optimize the FRGRE pulse sequence design and scanning parameters for enhanced cardiac MRI.
• To improve overall image quality and reduce artifacts in FRGRE cardiac imaging.

Main Methods:

• Implemented a 2D, multi-slice, multi-phase, breath-hold, segmented k-space, prospectively gated FRGRE sequence on a 1.5T GE Signa CV/i scanner.
• Investigated pulse sequence design changes using moment calculations and assessed cardiac image quality.
• Varied parameters including TE, TR, slice thickness, views per segment, and flip angle.

Main Results:

• Shortened TR (3.0 msec) and TE (0.9 msec) values were most influential in improving image quality.
• Placing the z gradient rephaser before the slice select gradient reduced moments and enhanced image quality.
• Increased slice thickness (8-10 mm) reduced flow artifact; doubling views per segment halved breath-hold time without quality loss.
• Optimal flip angle was ~60 degrees; flow compensation pulses unexpectedly decreased image quality.

Conclusions:

• Optimization of FRGRE sequence design and scanning parameters significantly reduces flow artifacts.
• The optimized FRGRE sequence offers improved image quality for cardiac MRI applications.
• Specific parameter adjustments, like TR/TE shortening and gradient rephaser placement, are key to artifact reduction.