Rofo 2007; 179 - A5
DOI: 10.1055/s-2007-972135

Towards distortion-free fMRI using highly accelerated parallel imaging with 32 channels at 3.0 Tesla

JF Utting 1, 2, M Tilbian 1, R Schnitker 2, M Kouwenhoven 3, T Niendorf 1
  • 1Department of Diagnostic Radiology, University of Aachen, Germany
  • 2IZKF-BIOMAT, University of Aachen, Germany
  • 3Philips Medical Systems, Best, The Netherlands

Purpose: The inherent sensitivity of Echo Planar Imaging (EPI) to inhomogeneity in the static magnetic field, B0, generates image distortion and signal loss, especially at high B0. This is particularly problematic for functional MRI. Spin-echo based techniques offer a distortion free-alternative to EPI [1]. Combined high B0 and parallel imaging with high acceleration factors (R) promise increased SNR and reduced acquisition times. The aims of this study are (i) to compare parallel imaging using SENSE [2] and the spatio-temporal correlation (k-t) approach [3], combined with EPI and TSE, with non-accelerated acquisitions; and (ii) to investigate the use of a 32 element coil array for highly accelerated brain imaging.

Methods: Imaging was performed at 3.0 Tesla (Philips Medical Systems, Best, The Netherlands), using eight-channel head and 32-channel coils, the latter combined with a purpose-built head holder. Imaging parameters: matrix 64×64; FOV=230×184mm; TR=2800ms (EPI), 3905ms (TSE); TE=19.5ms; SENSE and (TSE only) k-t with R=2, 4, 8, 12.

Results: The 8-channel head coil yielded good image quality for EPI and TSE with modest R. However, for R >2 the 32 channel coil produced less marked image artefacts, while reducing acquisitions times. Noise amplification associated with SENSE remains a concern for TSE techniques at higher R, but was minimal in k-t images.

Conclusion: Whole brain coverage within 1–2 seconds may be achieved by the combination of high B0 and parallel imaging with many element coil arrays. Significant steps towards this goal are demonstrated in this work.

References:

1. Niendorf, T., On the application of susceptibility-weighted ultra-fast low-angle RARE experiments in functional MR imaging. Magn Reson Med, 1999. 41(6): p.1189–1198.

2. Pruessmann, K.P., et al., SENSE: Sensitivity encoding for fast MRI. Magn Reson Med, 1999. 42(5): p.952–962.

3. Tsao, J., P. Boesiger, and K.P. Pruessmann, k-t BLAST and k-t SENSE: Dynamic MRI with high frame rate exploiting spatiotemporal correlations. Magn Reson Med, 2003. 50(5): p.1031–1042.