J-refocused coherence transfer spectroscopic imaging at 7 T in human brain

Area of Science:

• Neuroimaging
• Magnetic Resonance Spectroscopy
• Biophysics

Background:

• Short echo time (TE) acquisitions in magnetic resonance spectroscopy (MRS) are susceptible to macromolecule interference, complicating baseline determination.
• J-evolution of cerebral amino acids causes signal modulation, which is problematic for accurate quantification.

Purpose of the Study:

• To implement and validate a double echo J-refocused coherence transfer sequence at 7 Tesla (T) for improved MRS.
• To minimize J-modulation of amino acids and reduce macromolecule signal interference.

Main Methods:

• A double echo J-refocused coherence transfer sequence with an echo time (TE) of 34 msec was implemented at 7 T.
• Radiofrequency (RF) shimming with a transceiver array ensured B(1) sufficiency.
• Alternate RF distribution minimized receiver phase cancellation for accurate phase determination.

Main Results:

• Simulations at 7 T demonstrated excellent resolution of glutamate, glutamine, and N-acetyl aspartate.
• The method achieved accurate phase determination for coherence transfer with rapid single scan calibration.
• Spectroscopic imaging in healthy volunteers yielded metabolite values consistent with existing literature.

Conclusions:

• The developed double echo sequence effectively minimizes J-modulation and macromolecule interference at 7 T.
• This technique offers improved accuracy for metabolite quantification in neurological studies.
• The method shows promise for clinical applications, as demonstrated in an epilepsy patient.