title: Reproducibility of brain metabolite concentration measurements in lesion free white matter at 1.5 T.
abstract: BACKGROUND
  Post processing for brain spectra has a great influence on the fit quality of individual spectra, as well as on the reproducibility of results from comparable spectra. This investigation used pairs of spectra, identical in system parameters, position and time assumed to differ only in noise. The metabolite amplitudes of fitted time domain spectroscopic data were tested on reproducibility for the main brain metabolites.
  
  
  METHODS
  Proton spectra of white matter brain tissue were acquired with a short spin echo time of 30 ms and a moderate repetition time of 1500 ms at 1.5 T. The pairs were investigated with one time domain post-processing algorithm using different parameters. The number of metabolites, the use of prior knowledge, base line parameters and common or individual damping were varied to evaluate the best reproducibility.
  
  
  RESULTS
  The protocols with most reproducible amplitudes for N-acetylaspartate, creatine, choline, myo-inositol and the combined Glx line of glutamate and glutamine in lesion free white matter have the following common features: common damping of the main metabolites, a baseline using only the points of the first 10 ms, no additional lipid/macromolecule lines and Glx is taken as the sum of separately fitted glutamate and glutamine. This parameter set is different to the one delivering the best individual fit results.
  
  
  CONCLUSIONS
  All spectra were acquired in "lesion free" (no lesion signs found in MR imaging) white matter. Spectra of brain lesions, for example tumors, can be drastically different. Thus the results are limited to lesion free brain tissue. Nevertheless the application to studies is broad, because small alterations in brain biochemistry of lesion free areas had been detected nearby tumors, in patients with multiple sclerosis, drug abuse or psychiatric disorders.
  
  
  CONCLUSIONS
  Main metabolite amplitudes inside healthy brain can be quantified with a normalized root mean square deviation around 5 % using CH3 of creatine as reference. Only the reproducibility of myo-inositol is roughly twice as bad. The reproducibility should be similar using other references like internal or external water for an absolute concentration evaluation and are not influenced by relaxation corrections with literature values.
authors.affiliation: Grönemeyer Institut für Mikrotherapie, Universitätsstraße 142, D-44799, Bochum, Germany. busch@groenemeyer.com.
authors.forename: Martin H J
authors.initials: MH
authors.lastname: Busch
authors.affiliation: Beuth Hochschule für Technik Berlin, Luxemburger Straße 10, D-13353, Berlin, Germany. vollmann@beuth-hochschule.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Vollmann
authors.affiliation: Grönemeyer Institut für Mikrotherapie, Universitätsstraße 142, D-44799, Bochum, Germany. mateiescu@groenemeyer.com.
authors.forename: Serban
authors.initials: S
authors.lastname: Mateiescu
authors.affiliation: Ruhr Universität Bochum, Universitätsstraße 150, D-44801, Bochum, Germany. manuel.stolze@rub.de.
authors.forename: Manuel
authors.initials: M
authors.lastname: Stolze
authors.affiliation: Amedo Smart Tracking Solutions, Universitätsstraße 142, D-44799, Bochum, Germany. deli@amedo-gmbh.com.
authors.forename: Martin
authors.initials: M
authors.lastname: Deli
authors.affiliation: Grönemeyer Institut für Mikrotherapie, Universitätsstraße 142, D-44799, Bochum, Germany. garmer@groenemeyer.com.
authors.forename: Marietta
authors.initials: M
authors.lastname: Garmer
authors.affiliation: Grönemeyer Institut für Mikrotherapie, Universitätsstraße 142, D-44799, Bochum, Germany. koca@groenemeyer.com.
authors.forename: Dietrich H W
authors.initials: DH
authors.lastname: Grönemeyer
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D055442:Metabolome; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D066127:White Matter / Q000378:metabolism*