title: Combining phase and magnitude information for contrast agent quantification in dynamic contrast-enhanced MRI using statistical modeling.
abstract: OBJECTIVE
  The purpose of this study was to investigate, using simulations, a method for improved contrast agent (CA) quantification in DCE-MRI.
  
  
  METHODS
  We developed a maximum likelihood estimator that combines the phase signal in the DCE-MRI image series with an additional CA estimate, e.g. the estimate obtained from magnitude data. A number of simulations were performed to investigate the ability of the estimator to reduce bias and noise in CA estimates. Noise levels ranging from that of a body coil to that of a dedicated head coil were investigated at both 1.5T and 3T.
  
  
  RESULTS
  Using the proposed method, the root mean squared error in the bolus peak was reduced from 2.24 to 0.11 mM in the vessels and 0.16 to 0.08 mM in the tumor rim for a noise level equivalent of a 12-channel head coil at 3T. No improvements were seen for tissues with small CA uptake, such as white matter.
  
  
  CONCLUSIONS
  Phase information reduces errors in the estimated CA concentrations. A larger phase response from higher field strengths or higher CA concentrations yielded better results. Issues such as background phase drift need to be addressed before this method can be applied in vivo.
authors.affiliation: Department of Radiation Physics, Umeå University, Umeå, Sweden.
authors.forename: Patrik
authors.initials: P
authors.lastname: Brynolfsson
authors.affiliation: Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden.
authors.forename: Jun
authors.initials: J
authors.lastname: Yu
authors.affiliation: Department of Medical Radiation Physics, Lund University, Lund, Sweden.
authors.forename: Ronnie
authors.initials: R
authors.lastname: Wirestam
authors.affiliation: Department of Radiation Physics, Umeå University, Umeå, Sweden.
authors.forename: Mikael
authors.initials: M
authors.lastname: Karlsson
authors.affiliation: Department of Radiation Physics, Umeå University, Umeå, Sweden.|CJ Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, Netherlands.
authors.forename: Anders
authors.initials: A
authors.lastname: Garpebring
mesh_terms: D001921:Brain / Q000033:anatomy & histology / Q000473:pathology; D001932:Brain Neoplasms / Q000473:pathology; D003287:Contrast Media; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008954:Models, Biological; D015233:Models, Statistical; D019047:Phantoms, Imaging; D012815:Signal Processing, Computer-Assisted
chemical_list: D003287:Contrast Media
keywords: contrast agent quantification; dynamic contrast-enhanced MRI; inverse problem; phase