(2 + 1)D-CAIPIRINHA accelerated MR spectroscopic imaging of the brain at 7T
Magnetic Resonance in Medicine
Purpose: To compare a new parallel imaging (PI) method for multislice proton magnetic resonance spectroscopic imaging ( 1 H-MRSI), termed (2 þ 1)D-CAIPIRINHA, with two standard PI methods: 2D-GRAPPA and 2D-CAIPIRINHA at 7 Tesla (T). Methods: (2 þ 1)D-CAIPIRINHA is a combination of 2D-CAIPIRINHA and slice-CAIPIRINHA. Eight healthy volunteers were measured on a 7T MR scanner using a 32-channel head coil. The best undersampling patterns were estimated for all three PI methods. The artifact powers,
... g-factors, Cram er-Rao lower bounds (CRLB), and root mean square errors (RMSE) were compared quantitatively among the three PI methods. Metabolic maps and spectra were compared qualitatively. Results: (2 þ 1)D-CAIPIRINHA allows acceleration in three spatial dimensions in contrast to 2D-GRAPPA and 2D-CAIPIRINHA. Thus, this sequence significantly decreased the RMSE of the metabolic maps by 12.1 and 6.9%, on average, for 4 < R < 11, compared with 2D-GRAPPA and 2D-CAIPIRINHA, respectively. The artifact power was 22.6 and 8.4% lower, and the CRLB were 3.4 and 0.6% lower, respectively. Conclusion: (2 þ 1)-CAIPIRINHA can be implemented for multislice MRSI in the brain, enabling higher accelerations than possible with two-dimensional (2D) parallel imaging methods. An eight-fold acceleration was still feasible in vivo with negligible PI artifacts with lipid decontamination, thus decreasing the measurement time from 120 to 15 min for a 64 Â 64 Â 4 matrix.