title: Finite magnetic relaxation in x-space magnetic particle imaging: Comparison of measurements and ferrohydrodynamic models.
abstract: Magnetic Particle Imaging (MPI) is an emerging tomographic imaging technology that detects magnetic nanoparticle tracers by exploiting their non-linear magnetization properties. In order to predict the behavior of nanoparticles in an imager, it is possible to use a non-imaging MPI relaxometer or spectrometer to characterize the behavior of nanoparticles in a controlled setting. In this paper we explore the use of ferrohydrodynamic magnetization equations for predicting the response of particles in an MPI relaxometer. These include a magnetization equation developed by Shliomis (Sh) which has a constant relaxation time and a magnetization equation which uses a field-dependent relaxation time developed by Martsenyuk, Raikher and Shliomis (MRSh). We compare the predictions from these models with measurements and with the predictions based on the Langevin function that assumes instantaneous magnetization response of the nanoparticles. The results show good qualitative and quantitative agreement between the ferrohydrodynamic models and the measurements without the use of fitting parameters and provide further evidence of the potential of ferrohydrodynamic modeling in MPI.
authors.affiliation: Department of Chemical Engineering, University of Florida, 1030 Center Drive, Gainesville, FL 32611, USA.
authors.forename: R
authors.initials: R
authors.lastname: Dhavalikar
authors.affiliation: Department of Bioengineering, University of California, Berkeley, CA 94720, USA.
authors.forename: D
authors.initials: D
authors.lastname: Hensley
authors.affiliation: Department of Chemical Engineering, University of Florida, 1030 Center Drive, Gainesville, FL 32611, USA.
authors.forename: L
authors.initials: L
authors.lastname: Maldonado-Camargo
authors.affiliation: Department of Bioengineering, University of California, Berkeley, CA 94720, USA.
authors.forename: L R
authors.initials: LR
authors.lastname: Croft
authors.affiliation: Department of Mechanical and Aerospace Engineering, University of Florida, 231 MAE-A, Gainesville, FL 32611, USA.
authors.forename: S
authors.initials: S
authors.lastname: Ceron
authors.affiliation: Magnetic Insight, Inc. Newark, CA 94560, USA.
authors.forename: P W
authors.initials: PW
authors.lastname: Goodwill
authors.affiliation: Department of Bioengineering, University of California, Berkeley, CA 94720, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Conolly
authors.affiliation: Department of Chemical Engineering, University of Florida, 1030 Center Drive, Gainesville, FL 32611, USA; J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida,1275 Center Drive, Gainesville, FL 32611 ,USA.
authors.forename: C
authors.initials: C
authors.lastname: Rinaldi
keywords: Magnetic particle imaging (MPI); ferrohydrodynamics; relaxation; x-space MPI