T2* BOLD Contrast Brain Imaging at 7.0 T: Echo Planar Imaging vs. Single Shot Turbo Spin Echo

Purpose: MRI at high magnetic field strengths promises a more comprehensive understanding of the human brain through improved localisation of functional activation. This potential is accompanied by challenges including increased B₀ inhomogeneity and RF power deposition.

The aim of this study is optimal imaging for functional MRI at 7.0 Tesla. EPI and displaced UFLARE – a single-shot spin echo variant – were combined with parallel imaging to mitigate image distortion and signal drop-out in EPIand reduce RF power deposition in UFLARE.

Materials and Methods: Images were acquired at 7.0 T (Achieva, Philips Medical Systems, Best, Netherlands), using a sixteen channel receive- and a volume transmit coil (Nova Medical, Wilmington, MA, USA); 128×128 matrix; 4000ms TR; TE of 24ms for EPI, 38ms for UFLARE with echo shift (τ) of 20ms and 100⁰ refocusing RF pulses to restrict power deposition. SENSE and “k-t“ parallel imaging were applied.

Results: Distortion free T₂*-weighted images at 7.0 T were acquired with displaced UFLARE. A SENSE factor R=2 considerably improved the quality of EPI. Higher SENSE factors caused significant artifacts in both EPI and UFLARE images.However, the k-t technique is less sensitive to coil design and lends itself to the temporally varying signals of fMRI.

Conclusion: Displaced UFLARE offers the flexibility of T₂ or (variable) T₂*-weighting and the resulting image contrast and anatomical fidelity may contribute to improved localisation of brain activation, especially at ultra-high B₀. Displaced UFLARE combined with k-t presents a promising approach for fMRI at 7.0 T.