Simultaneous multislice imaging in dynamic cardiac MRI at 7T using parallel transmission.

Area of Science:

• Magnetic Resonance Imaging
• Cardiovascular Imaging
• Biomedical Engineering

Background:

• 7T Cardiac MRI faces challenges with contrast heterogeneity and limited slice coverage during breath-holds.
• Parallel transmission (pTX) can mitigate contrast issues, while simultaneous multi-band (MB) radiofrequency pulses (SMS) increase the number of simultaneously excited slices.

Purpose of the Study:

• To simultaneously apply parallel transmission (pTX) and simultaneous multi-band (MB) excitation (SMS) for improved 7T cardiac MRI.
• To evaluate the effectiveness of combined pTX and SMS techniques in addressing contrast heterogeneity and increasing slice coverage.

Main Methods:

• A 16-channel transmit/receive body coil was used with pTX SMS and CAIPIRINHA.
• Modified gradient echo cine sequences were employed, investigating different calibration schemes for slice-GRAPPA reconstruction kernels across the cardiac cycle.

Main Results:

• CAIPIRINHA achieved excellent slice separation (MB=2) with minimal slice leakage (<3%).
• Cardiac cycle variations in MB leakage (up to 30%) were significantly reduced by calibrating reconstruction kernels on multiple phases.
• Acceptable results were maintained with MB=3 and in-plane GRAPPA, and two-spoke pulses improved homogeneity.

Conclusions:

• Combined pTX SMS imaging at 7T effectively addresses contrast heterogeneity in cardiac MRI.
• This approach enables larger slice coverage for breath-hold cardiac MRI scans.
• The study demonstrates the feasibility and benefits of integrating advanced acceleration techniques in high-field cardiac MRI.