title: Simultaneous imaging and R2* mapping using a radial multi-gradient-echo (rMGE) sequence.
abstract: OBJECTIVE
  To demonstrate a rapid MR technique that combines imaging and R2* mapping based on a single radial multi-gradient-echo (rMGE) data set. The technique provides a fast method for online monitoring of the administration of (super-)paramagnetic contrast agents as well as image-guided drug delivery.
  
  
  METHODS
  Data are acquired using an rMGE sequence, resulting in interleaved undersampled radial k-spaces representing different echo times (TEs). These data sets are reconstructed separately, yielding a series of images with different TEs used for pixelwise R2* mapping. A fast numerical algorithm implemented on a real-time reconstruction platform provides online estimation of the relaxation rate R2*. Simultaneously the images are summed for the computation of a high-resolution image.
  
  
  RESULTS
  Convenient high-resolution R2* maps of phantoms and the liver of a healthy volunteer were obtained. In addition to stable intrinsic baseline maps, the proposed technique provides particularly accurate results for the high relaxation rates observed during the presence of (super-)paramagnetic contrast agents. Assuming that the change in R2* is proportional to the concentration of the agent, the technique offers a rough estimate for dynamic dosage.
  
  
  CONCLUSIONS
  The simultaneous online display of morphological and parametric information permits convenient, quantitative surveillance of contrast-agent administration.
authors.affiliation: Institute of Biomedical Engineering, University of Karlsruhe, Karlsruhe, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Winkelmann
authors.forename: Tobias
authors.initials: T
authors.lastname: Schaeffter
authors.forename: Steffen
authors.initials: S
authors.lastname: Weiss
authors.forename: Holger
authors.initials: H
authors.lastname: Eggers
authors.forename: Olaf
authors.initials: O
authors.lastname: Doessel
mesh_terms: D000465:Algorithms; D003287:Contrast Media / Q000008:administration & dosage; D003911:Dextrans; D052203:Ferrosoferric Oxide; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007501:Iron / Q000008:administration & dosage; D008099:Liver / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D010087:Oxides / Q000008:administration & dosage; D019047:Phantoms, Imaging
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D010087:Oxides; D007501:Iron; C065507:ferumoxides; D052203:Ferrosoferric Oxide