System stability of a 3T-MRI during continuous EPI scan

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Neuroimaging
• Biomedical Engineering

Background:

• The ATR-Brain Activity Imaging Center (ATR-BAIC) routinely uses echo planar imaging (EPI) for extended durations (up to 30 min).
• Ensuring the stability and consistent image quality of EPI sequences is crucial for reliable neuroimaging research.
• Evaluating new MRI hardware, such as a 3 Tesla (3T) system, against established systems (1.5T) is essential for optimizing imaging protocols.

Purpose of the Study:

• To assess the general stability and image characteristics of a newly installed 3T MRI system.
• To compare the performance of the 3T system with a conventional 1.5T system, focusing on EPI sequences.
• To identify potential limitations and advantages of the 3T system for long-duration EPI scans.

Main Methods:

• Comparative analysis of image stability and quality metrics between 1.5T and 3T MRI systems.
• Focus on echo planar imaging (EPI) sequences, including evaluation of image shifts, signal fluctuations, and temporal signal-to-noise ratio (TSNR).
• Long-term data acquisition to assess stability over extended scanning periods (up to 30 minutes).

Main Results:

• The 3T system demonstrated significantly reduced image shifts compared to the 1.5T system, despite similar B0 shift levels.
• Signal fluctuations were substantially lower (1/2-1/3 reduction) in the 3T system.
• The 3T system achieved a higher temporal signal-to-noise ratio (TSNR), with improvements of 1.7-2.0x (CP-coil) and 2.5-4.0x (12ch-coil) over the 1.5T system.
• Low-frequency periodic fluctuations and increased noise were observed in the latter half of long 3T scans.
• Spatial non-uniformity of TSNR and linear trends in voxels were noted in the 3T data.

Conclusions:

• The 3T MRI system offers enhanced stability and superior image quality for EPI compared to the 1.5T system.
• While generally improved, potential issues like periodic fluctuations and spatial non-uniformity in the 3T system require further investigation and optimization.
• The findings support the utility of the 3T system for advanced neuroimaging applications requiring high-quality EPI data.