title: Influence of echo time in quantitative proton MR spectroscopy using LCModel.
abstract: OBJECTIVE
  The objective of this study was to elucidate the influence on quantitative analysis using LCModel with the condition of echo time (TE) longer than the recommended values in the spectrum acquisition specifications.
  
  
  METHODS
  A 3T magnetic resonance system was used to perform proton magnetic resonance spectroscopy. The participants were 5 healthy volunteers and 11 patients with glioma. Data were collected at TE of 72, 144 and 288ms. LCModel was used to quantify several metabolites (N-acetylaspartate, creatine and phosphocreatine, and choline-containing compounds). The results were compared with quantitative values obtained by using the T2-corrected internal reference method.
  
  
  RESULTS
  In healthy volunteers, when TE was long, the quantitative values obtained using LCModel were up to 6.8-fold larger (p<0.05) than those obtained using the T2-corrected internal reference method. The ratios of the quantitative values obtained by the two methods differed between metabolites (p<0.05). In patients with glioma, the ratios of quantitative values obtained by the two methods tended to be larger at longer TE, similarly to the case of healthy volunteers, and large between-individual variation in the ratios was observed.
  
  
  CONCLUSIONS
  In clinical practice, TE is sometimes set longer than the value recommended for LCModel. If TE is long, LCModel overestimates the quantitative value since it cannot compensate for signal attenuation, and this effect is different for each metabolite and condition. Therefore, if TE is longer than recommended, it is necessary to account for the possibly reduced reliability of quantitative values calculated using LCModel.
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Tsukuba.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Graduate School of Comprehensive Human Sciences, University of Tsukuba. Electronic address: tiso@md.tsukuba.ac.jp.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Isobe
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Tsukuba.
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Akutsu
authors.affiliation: Department of Radiology, Faculty of Medicine, University of Tsukuba.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Masumoto
authors.affiliation: Graduate School of Comprehensive Human Sciences, University of Tsukuba.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ando
authors.affiliation: Graduate School of Comprehensive Human Sciences, University of Tsukuba.
authors.forename: Eisuke
authors.initials: E
authors.lastname: Sato
authors.affiliation: Graduate School of Comprehensive Human Sciences, University of Tsukuba.
authors.forename: Kenta
authors.initials: K
authors.lastname: Takada
authors.affiliation: Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences.
authors.forename: Izumi
authors.initials: I
authors.lastname: Anno
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Tsukuba.
authors.forename: Akira
authors.initials: A
authors.lastname: Matsumura
mesh_terms: D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001921:Brain / Q000378:metabolism; D001932:Brain Neoplasms / Q000378:metabolism*; D002794:Choline / Q000378:metabolism; D003401:Creatine / Q000378:metabolism; D005910:Glioma / Q000378:metabolism*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008962:Models, Theoretical; D010725:Phosphocreatine / Q000378:metabolism; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results
chemical_list: D010725:Phosphocreatine; D001224:Aspartic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline
keywords: Echo time; LCModel; MRS; Quantitative analysis; T2 relaxation