title: Enhancement of spectral editing efficacy of multiple quantum filters in in vivo proton magnetic resonance spectroscopy.
abstract: The performance of multiple quantum filters (MQFs) can be disappointing when the background signal also arises from coupled spins. Moreover, at 3.0 T and even higher fields the majority of the spin systems of key brain metabolites fall into the strong-coupling regime. In this manuscript we address comprehensively, the importance of the phase of the multiple quantum coherence-generating pulse (MQ-pulse) in the design of MQFs, using both product operator and numerical analysis, in both zero and double quantum filter designs. The theoretical analyses were experimentally validated with the examples of myo-inositol editing and the separation of glutamate from glutamine. The results demonstrate that the phase of the MQ-pulse per se provides an additional spectral discrimination mechanism based on the degree of coupling beyond the conventional level-of-coherence approach of MQFs. To obtain the best spectral discrimination of strongly-coupled spin systems, therefore, the phase of the MQ-pulse must be included in the portfolio of the sequence parameters to be optimized.
authors.affiliation: Department of Radiology, Seoul National University Hospital, Seoul, Republic of Korea. hyeonjinkim@snu.ac.kr
authors.forename: Hyeonjin
authors.initials: H
authors.lastname: Kim
authors.forename: Richard B
authors.initials: RB
authors.lastname: Thompson
authors.forename: Peter S
authors.initials: PS
authors.lastname: Allen
mesh_terms: D000465:Algorithms; D001923:Brain Chemistry; D002951:Citrates / Q000737:chemistry; D018698:Glutamic Acid / Q000737:chemistry; D005973:Glutamine / Q000737:chemistry; D006801:Humans; D007294:Inositol / Q000737:chemistry; D019344:Lactic Acid / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D019047:Phantoms, Imaging; D011522:Protons
chemical_list: D002951:Citrates; D011522:Protons; D005973:Glutamine; D019344:Lactic Acid; D018698:Glutamic Acid; D007294:Inositol