title: A rapid inversion technique for the measurement of longitudinal relaxation times of brain metabolites: application to lactate in high-grade gliomas at 3 T.
abstract: The aim of this study was to develop a time-efficient inversion technique to measure the T1 relaxation time of the methyl group of lactate (Lac) in the presence of contaminating lipids and to measure T1 at 3 T in a cohort of primary high-grade gliomas. Three numerically optimized inversion times (TIs) were chosen to minimize the expected error in T1 estimates for a given input total scan duration (set to be 30 min). A two-cycle spectral editing scheme was used to suppress contaminating lipids. The T1 values were then estimated from least-squares fitting of signal measurements versus TI. Lac T1 was estimated as 2000 ± 280 ms. After correcting for T1 (and T2 from literature values), the mean absolute Lac concentration was estimated as 4.3 ± 2.6 mm. The technique developed agrees with the results obtained by standard inversion recovery and can be used to provide rapid T1 estimates of other spectral components as required. Lac T1 exhibits similar variations to other major metabolites observable by MRS in high-grade gliomas. The T1 estimate provided here will be useful for future MRS studies wishing to report relaxation-corrected estimates of Lac concentration as an objective tumor biomarker. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Department of Medical Biophysics, University of Toronto, ON, Canada. landheer@sri.utoronto.ca.|Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada. landheer@sri.utoronto.ca.
authors.forename: Karl
authors.initials: K
authors.lastname: Landheer
authors.affiliation: Department of Radiation Oncology, Sunnybrook Odette Cancer Center, University of Toronto, ON, Canada.
authors.forename: Arjun
authors.initials: A
authors.lastname: Sahgal
authors.affiliation: Department of Radiation Oncology, Sunnybrook Odette Cancer Center, University of Toronto, ON, Canada.
authors.forename: Sten
authors.initials: S
authors.lastname: Myrehaug
authors.affiliation: GE Healthcare, Toronto, ON, Canada.
authors.forename: Albert P
authors.initials: AP
authors.lastname: Chen
authors.affiliation: Department of Medical Biophysics, University of Toronto, ON, Canada.|Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada.
authors.forename: Charles H
authors.initials: CH
authors.lastname: Cunningham
authors.affiliation: Department of Medical Biophysics, University of Toronto, ON, Canada.|Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Graham
mesh_terms: D000465:Algorithms; D014408:Biomarkers, Tumor / Q000378:metabolism*; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D005910:Glioma / Q000000981:diagnostic imaging / Q000378:metabolism*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D019344:Lactic Acid / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods*; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D014018:Tissue Distribution
chemical_list: D014408:Biomarkers, Tumor; D019344:Lactic Acid
keywords: MRS; brain tumor spectroscopy; in vivo spectroscopy; lactate; longitudinal relaxation time; quantitative spectroscopy