title: Improvement of gagCEST imaging in the human lumbar intervertebral disc by motion correction.
abstract: OBJECTIVE
  To investigate whether motion correction improves glycosaminoglycan chemical exchange saturation transfer imaging (gagCEST imaging) of intervertebral discs (IVDs).
  
  
  METHODS
  Magnetic resonance gagCEST imaging of 12 volunteers was obtained in lumbar IVDs at 3 T using a prototype pulse sequence. The data were motion-corrected using a prototype diffeomorphism-based motion compensation technique. For both the data with and that without motion correction (datac, datauc), CEST evaluation was performed using the magnetisation transfer ratio asymmetry (MTRasym) as a means of quantifying CEST effects. MTRasym and the signal-to-noise ratio (SNR) of the MTRasym map in the nucleus pulposus (NP) were compared for datac and datauc. A visual grading analysis was performed by a radiologist in order to subjectively quantify the quality of the MTRasym analysis (score 1: best quality, score 5: worst quality). Furthermore, a landmark analysis was performed in order to objectively quantify the motion between CEST images using the mean landmark distance dmean.
  
  
  RESULTS
  MTRasym and SNR were significantly higher for the motion-corrected data than for the uncorrected CEST data (MTRasym(datac) = 3.77 % ± 0.95 %, MTRasym(datauc) = 3.41 % ± 1.54 %, p value = 0.001; SNR(datac) = 3.88 ± 2.04, SNR(datauc) = 2.77 ± 1.55, p value < 0.001, number of IVDs = 48). The visual grading analysis revealed a higher reliability for datac (maximum score = 2) compared with datauc (maximum score = 5). The landmark analysis demonstrated the superiority of the motion-corrected data (dmean(datac) = 0.08 mm ± 0.09 mm, dmean(datauc) = 0.36 mm ± 0.09 mm, p value = 0.001).
  
  
  CONCLUSIONS
  Our study showed significant improvements in the ability to quantify CEST imaging in IVDs after the application of motion correction compared with uncorrected datasets.
authors.affiliation: Medical Faculty, Department of Diagnostic and Interventional Radiology, University Dusseldorf, Moorenstrasse 5, 40225, Dusseldorf, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Müller-Lutz
authors.forename: Christoph
authors.initials: C
authors.lastname: Schleich
authors.forename: Benjamin
authors.initials: B
authors.lastname: Schmitt
authors.forename: Melike
authors.initials: M
authors.lastname: Topgöz
authors.forename: Gael
authors.initials: G
authors.lastname: Pentang
authors.forename: Gerald
authors.initials: G
authors.lastname: Antoch
authors.forename: Hans-Jörg
authors.initials: HJ
authors.lastname: Wittsack
authors.forename: Falk
authors.initials: F
authors.lastname: Miese
mesh_terms: D000328:Adult; D005260:Female; D006025:Glycosaminoglycans / Q000378:metabolism*; D006801:Humans; D007403:Intervertebral Disc / Q000378:metabolism*; D008159:Lumbar Vertebrae / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009038:Motion; D012016:Reference Values; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio; D055815:Young Adult
chemical_list: D006025:Glycosaminoglycans