Self-gated cine phase-contrast balanced SSFP flow quantification at 0.55 T

Area of Science:

• Cardiovascular Imaging
• Magnetic Resonance Imaging
• Biophysics

Background:

• Cardiac MRI often requires electrocardiogram (ECG) gating for accurate flow quantification.
• Low-field MRI systems present challenges for achieving high-quality imaging and flow measurements.
• Balanced SSFP (bSSFP) sequences are known for speed but typically lack intrinsic flow sensitivity.

Purpose of the Study:

• To implement and validate cine phase-contrast balanced SSFP (PC-bSSFP) for low-field (0.55T) cardiac MRI.
• To enable self-gated and referenceless PC-bSSFP flow quantification in the aorta.
• To leverage radial trajectories and bSSFP properties for improved flow sensitivity and reduced scan times.

Main Methods:

• A free-running, tiny golden-angle radial PC-bSSFP sequence was developed and tested on 0.55T and 1.5T systems.
• Cardiac and respiratory self-gating was integrated for ECG-free scanning during breath-hold and free-breathing.
• Referenceless single-point PC-bSSFP was achieved using in-plane phase-cancelation and background phase fitting.

Main Results:

• PC-bSSFP provided high-quality cine magnitude and phase images at 0.55T with sufficient SNR and velocity-to-noise ratio.
• Flow quantification by PC-bSSFP closely matched phase-contrast spoiled gradient-echo methods (RMSEv = 5.8 cm/s).
• Referenceless PC-bSSFP results agreed well with two-point PC-bSSFP, reducing scan time by 50%.

Conclusions:

• PC-bSSFP is a feasible technique for low-field (0.55T) cardiac MRI.
• It allows simultaneous, high-quality aortic flow measurements during breath-hold and free-breathing without ECG gating.
• This approach offers a promising alternative for accessible cardiac flow assessment.