title: A preliminary study of the effects of trigger timing on diffusion tensor imaging of the human spinal cord.
abstract: OBJECTIVE
  Diffusion tensor and diffusion-weighted spinal cord imaging remain relatively unexplored techniques despite demonstrations that such images can be obtained and may yield clinically relevant findings. In this study, we examined the temporal dynamics of spinal cord motion and their impact on diffusion tensor image quality.
  
  
  METHODS
  Four healthy volunteers underwent phase contrast-based velocity mapping and segmented echo-planar diffusion tensor scans of the cervical spinal cord. Regions of interest in the cord were used to identify the temporal patterns of motion. The delay of data acquisition after the cardiac trigger was varied to correspond to either quiescence or motion of the cord.
  
  
  RESULTS
  The cervical spinal cord consistently displayed maximal velocities in the range of 0.5 cm/s and accelerations of up to 25 cm/s(2). In both these respects, the cervical cord values were greater than those of the medulla. Despite this pronounced motion, approximately 40% of the cardiac cycle can be described as relatively calm, with absolute velocities and accelerations less than 20% of the maximum values. Confining image acquisition to this window reduced ghosting artifacts and increased the consistency with which the dominant direction of diffusion was along the rostral-caudal axis in both gray and white matter of the spine. Preliminary clinical application and fiber tracking in pathologic cases was feasible, and alterations of the diffusion properties by multiple sclerosis lesions, tumor, and syringomyelia were seen.
  
  
  CONCLUSIONS
  Acquiring DTI data during the quiescent phase of spinal cord motion can reduce ghosting artifacts and improve fiber tracking.
authors.affiliation: Institute for Neuroradiology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Summers
authors.forename: P
authors.initials: P
authors.lastname: Staempfli
authors.forename: T
authors.initials: T
authors.lastname: Jaermann
authors.forename: S
authors.initials: S
authors.lastname: Kwiecinski
authors.forename: S
authors.initials: S
authors.lastname: Kollias
mesh_terms: D000328:Adult; D016880:Anisotropy; D016477:Artifacts; D003971:Diastole / Q000502:physiology; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008526:Medulla Oblongata / Q000473:pathology / Q000503:physiopathology; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D009412:Nerve Fibers / Q000473:pathology / Q000502:physiology; D010092:Oximetry / Q000379:methods; D012680:Sensitivity and Specificity; D013116:Spinal Cord / Q000473:pathology / Q000503:physiopathology*; D013122:Spinal Diseases / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D013599:Systole / Q000502:physiology; D013997:Time Factors