title: Prospective motion correction for magnetic resonance spectroscopy using single camera Retro-Grate reflector optical tracking.
abstract: OBJECTIVE
  To introduce and evaluate a method of prospective motion correction for localized proton magnetic resonance spectroscopy (1H-MRS) using a single-camera optical tracking system.
  
  
  METHODS
  Five healthy participants were scanned at 3T using a point-resolved spectroscopic sequence (PRESS) with a motion-tracking module and phase navigator. Head motion in six degrees was tracked with a Retro-Grate Reflector (RGR) tracking system and target via a mirror mounted inside the bore. Participants performed a series of three predetermined motion patterns during scanning.
  
  
  RESULTS
  Left-right rotation (Rz) (average 12°) resulted in an increase in the total choline to total creatine ratio (Cho/Cr) of +14.6 ± 1.5% (P = 0.0009) for scans without correction, but no change for scans with correction (+1.1 ± 1.5%; P = 0.76). Spectra with uncorrected Z-translations showed large lipid peaks (skull) with changes in Cho/Cr of -13.2 ± 1.6% (P = 0.02, no motion correction) and -2.2 ± 2.4% (P = 0.51) with correction enabled. There were no significant changes in the ratios of N-acetylaspartate, glutamate+glutamine, or myo-inositol to creatine compared to baseline scans for all experiments.
  
  
  CONCLUSIONS
  Prospective motion correction for 1H-MRS, using single-camera RGR tracking, can reduce spectral artifacts and quantitation errors in Cho/Cr ratios due to head motion and promises improved spectral quality and reproducibility.
authors.affiliation: Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu, Hawaii, USA.
authors.forename: Brian C
authors.initials: BC
authors.lastname: Andrews-Shigaki
authors.forename: Brian S R
authors.initials: BS
authors.lastname: Armstrong
authors.forename: Maxim
authors.initials: M
authors.lastname: Zaitsev
authors.forename: Thomas
authors.initials: T
authors.lastname: Ernst
mesh_terms: D000328:Adult; D016477:Artifacts; D015415:Biomarkers / Q000032:analysis*; D001921:Brain / Q000378:metabolism*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D008297:Male; D008875:Middle Aged; D009038:Motion; D055096:Optical Devices
chemical_list: D015415:Biomarkers