title: A phase rotation scheme for achieving very short echo times with localized stimulated echo spectroscopy.
abstract: In a single-voxel stimulated echo localization sequence in magnetic resonance spectroscopy, magnetic field gradients are inserted within the echo time (TE) to filter signals generated through coherence pathways other than that leading to the stimulated echo. There is a significant penalty for these gradients as they increase the minimum TE, thereby leading to significant signal loss from spin-spin relaxation and phase distortions in coupled spin systems. Here, an RF phase rotation technique is described for a stimulated echo localization sequence that allows removal of the gradients in the TE intervals and, subsequently, reduction of the minimum TE to only 6 ms. Experiments carried out on six healthy volunteers on a 1.5-T whole-body MR system show a significant signal increase in the metabolite concentrations when measured with a 6-ms TE (N-acetyl-aspartate, 12%, P=.002; creatine, 15%, P=.04; and glutamate+glutamine, 92%, P=.02) compared to concentrations measured with data collected at TEs of 15 and 20 ms.
authors.affiliation: Department of Biomedical Engineering, University of Virginia Health System, Charlottesville, VA 22908-0759, USA. jack.knight-scott@virginia.edu
authors.forename: Jack
authors.initials: J
authors.lastname: Knight-Scott
authors.forename: Dattesh D
authors.initials: DD
authors.lastname: Shanbhag
authors.forename: S Andrea
authors.initials: SA
authors.lastname: Dunham
mesh_terms: D000328:Adult; D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology*; D002794:Choline / Q000032:analysis; D003401:Creatine / Q000032:analysis; D004151:Dipeptides / Q000032:analysis; D005260:Female; D018698:Glutamic Acid / Q000032:analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007294:Inositol / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D019047:Phantoms, Imaging; D012016:Reference Values; D013997:Time Factors
chemical_list: D004151:Dipeptides; C027172:isospaglumic acid; D018698:Glutamic Acid; D007294:Inositol; D003401:Creatine; D002794:Choline