title: J-refocused coherence transfer spectroscopic imaging at 7 T in human brain.
abstract: Short echo spectroscopy is commonly used to minimize signal modulation due to J-evolution of the cerebral amino acids. However, short echo acquisitions suffer from high sensitivity to macromolecules which make accurate baseline determination difficult. In this report, we describe implementation at 7 T of a double echo J-refocused coherence transfer sequence at echo time (TE) of 34 msec to minimize J-modulation of amino acids while also decreasing interfering macromolecule signals. Simulation of the pulse sequence at 7 T shows excellent resolution of glutamate, glutamine, and N-acetyl aspartate. B(1) sufficiency at 7 T for the double echo acquisition is achieved using a transceiver array with radiofrequency (RF) shimming. Using an alternate RF distribution to minimize receiver phase cancellation in the transceiver, accurate phase determination for the coherence transfer is achieved with rapid single scan calibration. This method is demonstrated in spectroscopic imaging mode with n = 5 healthy volunteers resulting in metabolite values consistent with literature and in a patient with epilepsy.
authors.affiliation: Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut 06520-0882, USA. jullie.pan@yale.edu
authors.forename: J W
authors.initials: JW
authors.lastname: Pan
authors.forename: N
authors.initials: N
authors.lastname: Avdievich
authors.forename: H P
authors.initials: HP
authors.lastname: Hetherington
mesh_terms: D001704:Biopolymers / Q000032:analysis*; D001921:Brain / Q000033:anatomy & histology* / Q000378:metabolism*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D014018:Tissue Distribution
chemical_list: D001704:Biopolymers