title: Advantages and limitations of prospective head motion compensation for MRI using an optical motion tracking device.
abstract: OBJECTIVE
  Subject motion appears to be a limiting factor in numerous magnetic resonance (MR) imaging (MRI) applications. In particular, head tremor, which often accompanies stroke, may render certain high-resolution two- (2D) and three-dimensional (3D) techniques inapplicable. The reason for that is head movement during acquisition. The study objective is to achieve a method able to compensate for complete motion during data acquisition. The method should be usable for every sequence and easily implemented on different MR scanners.
  
  
  METHODS
  The possibility of interfacing the MR scanner with an external optical motion-tracking system capable of determining the object's position with submillimeter accuracy and an update rate of 60 Hz is shown. Movement information on the object position (head) is used to compensate for motion in real time by updating the field of view (FOV) by recalculating the gradients and radiofrequency parameter of the MR scanner during acquisition of k-space data, based on tracking data.
  
  
  RESULTS
  Results of rotation phantom, in vivo experiments, and implementation of three different MRI sequences, 2D spin echo, 3D gradient echo, and echo planar imaging, are presented. Finally, the proposed method is compared with the prospective motion correction software available on the scanner software.
  
  
  CONCLUSIONS
  A prospective motion correction method that works in real time only by updating the FOV of the MR scanner is presented. Results show the feasibility of using an external optical motion-tracking system to compensate for strong and fast subject motion during acquisition.
authors.affiliation: Department of Cognitive Computing and Medical Imaging, Fraunhofer Gesellschaft, Institute for Computer Graphics, Fraunhoferstr 5, D-64283 Darmstadt, Germany. christian.dold@igd.fraunhofer.de
authors.forename: Christian
authors.initials: C
authors.lastname: Dold
authors.forename: Maxim
authors.initials: M
authors.lastname: Zaitsev
authors.forename: Oliver
authors.initials: O
authors.lastname: Speck
authors.forename: Evelyn A
authors.initials: EA
authors.lastname: Firle
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hennig
authors.forename: Georgios
authors.initials: G
authors.lastname: Sakas
mesh_terms: D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology*; D017352:Echo-Planar Imaging / Q000295:instrumentation / Q000379:methods*; D019416:Head Movements; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D055095:Optics and Photonics / Q000295:instrumentation*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity