title: Reduction of voxel bleeding in highly accelerated parallel (1) H MRSI by direct control of the spatial response function.
abstract: OBJECTIVE
  To substantially improve spatial localization in magnetic resonance spectroscopic imaging (MRSI) accelerated by parallel imaging. This is important in order to make MRSI more reliable as a tool for clinical applications.
  
  
  METHODS
  The sensitivity encoding acceleration technique with spatial overdiscretization is applied for the reconstruction of parallel MRSI. In addition, the spatial response function is optimized by minimizing its deviation from a previously chosen target function. This modified minimum-norm sensitivity encoding-MRSI reconstruction approach is applied in this article for in vivo pulse-acquire MRSI of human brain at 7T with simulated acceleration factors of 2, 4, and 9 as well as actual 4-fold accelerated MRSI.
  
  
  RESULTS
  The sidelobes of the spatial response function are significantly suppressed, which reduces far-reaching voxel bleeding. At the same time, the major enlargement of the effective voxel size, which would be introduced by conventional k-space apodization methods, is largely avoided. Regularization allows for a practical trade-off between noise minimization, effective voxel size, and unaliasing. Although not aiming at increasing the nominal spatial resolution, a better spatial specificity is achieved.
  
  
  CONCLUSIONS
  Simultaneous suppression of short- and far-reaching voxel bleeding in MRSI is analyzed and reconstruction of highly accelerated parallel in vivo MRSI is demonstrated.
authors.affiliation: Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kirchner
authors.forename: Ariane
authors.initials: A
authors.lastname: Fillmer
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Tsao
authors.forename: Klaas Paul
authors.initials: KP
authors.lastname: Pruessmann
authors.forename: Anke
authors.initials: A
authors.lastname: Henning
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D062211:Spatio-Temporal Analysis; D014018:Tissue Distribution
keywords: magnetic resonance spectroscopic imaging; minimum-norm; sensitivity encoding; spatial response function; voxel bleeding