Contrast-optimal simultaneous multi-slice bSSFP cine cardiac imaging at 0.55 T

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Cardiovascular Imaging
• Medical Physics

Background:

• Balanced steady-state free precession (bSSFP) is valuable for cardiac function assessment.
• Simultaneous multi-slice (SMS) acceleration is desirable but faces challenges at conventional field strengths.
• Excessive specific absorption rate (SAR) and banding artifacts limit flip angle optimization in bSSFP at higher field strengths.

Purpose of the Study:

• To evaluate the feasibility of using contrast-optimal flip angles (FA) with SMS bSSFP for cardiac function assessment at 0.55T.
• To determine if this approach overcomes limitations of conventional field strengths.

Main Methods:

• Blipped-CAIPI bSSFP with spiral sampling was used for ventricular function assessment at 0.55T.
• Cine images were acquired with single band and SMS factors (2 and 3) across various flip angles (60°-160°).
• Left ventricular blood and myocardial signal intensity, normalized by background noise, and blood-myocardium contrast were analyzed.

Main Results:

• Myocardial signal intensity decreased with increasing FA, while blood signal intensity increased, particularly for single band up to ~100° for SMS.
• Blood-myocardium contrast peaked at specific FAs: 160° for single band, 120° for SMS 2, and 100°-120° for SMS 3.
• Optimal contrast was achieved with reduced myocardial signal at higher FAs.

Conclusions:

• Contemporary 0.55T MRI scanners with advanced gradients support contrast-optimal FA for SMS accelerated bSSFP cardiac cine imaging.
• This technique achieves high image quality without compromising cardiac function assessment.
• Contrast-optimal flip angles were identified as 140°-160° for single band and 100°-120° for SMS 2 and 3.