title: Iterative 3D projection reconstruction of (23) Na data with an (1) H MRI constraint.
abstract: OBJECTIVE
  To increase the signal-to-noise ratio (SNR) and to reduce artifacts in non-proton magnetic resonance imaging (MRI) by incorporation of a priori information from (1) H MR data in an iterative reconstruction.
  
  
  METHODS
  An iterative reconstruction algorithm for 3D projection reconstruction (3DPR) is presented that combines prior anatomical knowledge and image sparsity under a total variation (TV) constraint. A binary mask (BM) is used as an anatomical constraint to penalize non-zero signal intensities outside the object. The BM&TV method is evaluated in simulations and in MR measurements in volunteers.
  
  
  RESULTS
  In simulated BM&TV brain data, the artifact level was reduced by 20% while structures were well preserved compared to gridding. SNR maps showed a spatially dependent SNR gain over gridding reconstruction, which was up to 100% for simulated data. Undersampled 3DPR (23) Na MRI of the human brain revealed an SNR increase of 29 ± 7%. Small anatomical structures were reproduced with a mean contrast loss of 14%, whereas in TV-regularized iterative reconstructions a loss of 66% was found.
  
  
  CONCLUSIONS
  The BM&TV algorithm allows reconstructing images with increased SNR and reduced artifact level compared to gridding and performs superior to an iterative reconstruction using an unspecific TV constraint only.
authors.affiliation: Department of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Gnahm
authors.forename: Michael
authors.initials: M
authors.lastname: Bock
authors.forename: Peter
authors.initials: P
authors.lastname: Bachert
authors.forename: Wolfhard
authors.initials: W
authors.lastname: Semmler
authors.forename: Nicolas G R
authors.initials: NG
authors.lastname: Behl
authors.forename: Armin M
authors.initials: AM
authors.lastname: Nagel
mesh_terms: D000328:Adult; D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology* / Q000378:metabolism*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017670:Sodium Compounds / Q000378:metabolism*; D012975:Sodium Isotopes / Q000493:pharmacokinetics; D014018:Tissue Distribution; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; D017670:Sodium Compounds; D012975:Sodium Isotopes
keywords: anatomical prior knowledge; iterative reconstruction; non-proton MRI; projection reconstruction; sodium MRI