Prospective Motion Correction for Magnetic Resonance Spectroscopy Using Single Camera Retro-Grate Reflector Optical Tracking

Purpose: 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. Materials and 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 degrees) 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. Conclusion: 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.