title: Accuracy and reproducibility of a quantitative magnetic resonance imaging method for concurrent measurements of tissue relaxation times and proton density.
abstract: OBJECTIVE
  To evaluate the accuracy and reproducibility of a quantitative magnetic resonance (qMR) imaging method (QRAPMASTER) for simultaneous measurements of T1 and T2 relaxation times, and proton density (PD).
  
  
  METHODS
  Measurements of T1, T2, and PD with qMR were performed using phantoms with different relaxation times and concentrations of heavy water. Healthy volunteers were examined with different head coils. Regional measurements were performed in normal-appearing white and gray matter from the healthy control subjects, and in multiple sclerosis (MS) patients.
  
  
  RESULTS
  In phantom measurements, QRAPMASTER slightly underestimated T1, and T2 variations between repeated measurements were modest. PD was generally overestimated. The overall relative difference was -1.2±5.3% (T1), -6.6±1.9% (T2), and 0.7±5.1% (PD). In healthy volunteers, there were no statistically significant differences of T1, T2 or PD using different head coils. Values of T1, T2, and PD obtained in healthy controls and MS patients were within reference ranges. However, significant differences were found in normal-appearing gray and white matter.
  
  
  CONCLUSIONS
  QRAPMASTER can be considered a sufficiently accurate and reproducible method for use in clinical practice. Neuropathology in normal-appearing brain tissue may be revealed using this MR method, with putative implications for quantification of tissue damage in neurological diseases.
authors.affiliation: Department of Radiology, Faculty of Medicine and Health, Örebro University, Sweden. Electronic address: wolfgang.krauss@regionorebrolan.se.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Krauss
authors.affiliation: Department of Neurology and Neurophysiology, Faculty of Medicine and Health, Örebro University, Sweden; Faculty of Medicine and Health, Örebro University, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Gunnarsson
authors.affiliation: Faculty of Medicine and Health, Örebro University, Sweden.
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Andersson
authors.affiliation: Faculty of Medicine and Health, Örebro University, Sweden; Department of Medical Physics, Faculty of Medicine and Health, Örebro University, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Thunberg
mesh_terms: D000328:Adult; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009103:Multiple Sclerosis / Q000473:pathology*; D019047:Phantoms, Imaging; D011522:Protons; D015203:Reproducibility of Results
chemical_list: D011522:Protons
keywords: Multiple sclerosis; PD mapping; Quantitative MRI; Synthetic MRI; T1 mapping; T2 mapping